TAXONOMY AND ECOLOGY OF NEMATODES OFAGRICULTURAL FIELDS AND

WASTELANDS

THESIS

SUBMITTED FOR THE AWARD OF THE DEGREE OF

Doctor of Philosophy IN

ZOOLOGY

BY

GAURAV KUMAR SINGH

DEPARTMENT OF ZOOLOGY ALIGARH MUSLIM UNIVERSITY

ALIGARH (INDIA) 2011

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IRFAN AHMAD Ph.D. DEPARTMENT OF ZOOLOGY Professor Aligarh Muslim University,

Aligarh – 202002, INDIA ahmadirfi@gmail.com

Date: ………………….

Certificate

This is to certify that the research work presented in the thesis entitled,

“Taxonomy and Ecology of Nematodes of Agricultural Fields and Wastelands” by

Mr. Gaurav Kumar Singh is original and was carried out under my supervision. I have

permitted Mr. Singh to submit it to the Aligarh Muslim University, Aligarh in

fulfillment of the requirements for the degree of Doctor of Philosophy in Zoology.

IRFAN AHMAD (Supervisor)

Acknowledgements

I bow in deep reverence to GOD the Almighty, who blessed me with an innumerable favour of

academic work.

It has been a great opportunity for me to work under the able guidance of Prof. Irfan Ahmad,

Chairman, Department of Zoology, Aligarh Muslim University, Aligarh. I express my sincere

gratitude for his ever-lasting important advices, valuable suggestions, stimulating discussions,

constructive criticism, sense of perfection and precision which enabled me to complete this work. Inspite

of his tight departmental commitments he kept his door open wide for me. His affectionate instinct and

constant encouragement were always a boon to me. Any error if still remains is entirely my own.

I am thankful to the Chairmen (past and present), Department of Zoology, Aligarh Muslim

University, Aligarh for providing necessary laboratory facilities for the work.

I feel more than obliged to all my respected teachers Prof. M. Shamim Jairajpuri (INSA

Senior Scientist), Prof. Wasim Ahmad, Prof. Qudsia Tahseen and Prof. Mahalaqa Choudhary for

their valuable advices and kind suggestions.

I wish to acknowledge my seniors and lab colleagues, Dr. Noorus Sabah, Dr. Md.

Mahamood, Dr. Ali Asghar Shah, Mr. Puneet Kumar, Ms. Gazala Yousuf & Ms. Nadia Sufyan.

I am also thankful to my senior Dr. Md. Baniyamuddin and colleagues Dr. Shikha Ahlawat,

Ms. Uzma Tauheed, Mrs. Tabinda Nusrat , Ms. Malka Mustaqim and Ms. Sumaiya Ahad for

their constant inspirations and support.

Special thanks are due to my friend and colleague Vijay Vikram Singh for his unconditional

and constant help during compilation of this work.

Thanks are also due to my friends Imran and Vimal for their constant encouragement during

the course of present work.

Last but not the least, I would like to thank my wife for making me believe that I can do it and

my little angel for giving me cheers of my life.

My brothers Mr. Umesh Singh and Mr. Saurabh and my bhabhi Mrs. Meenakshi deserve

special thanks for creating ideal milieu at home which helped me to complete the present work.

The financial assistance from the Ministry of Environment and Forest, Government of India,

New Delhi is also thankfully acknowledged.

Gaurav Kumar Singh

CONTENTS

PART – A

Page

INTRODUCTION 1

HISTORICAL BACKGROUND 12

MATERIALS AND METHODS 21

SYSTEMATICS 24

ORDER RHABDITIDA 24

SUBORDER CEPHALOBINA 24

SUPERFAMILY CEPHALOBOIDEA 25

FAMILY CEPHALOBIDAE 26

SUBFAMILY CEPHALOBINAE 26

Genus Pseudacrobeles 27

Pseudacrobeles ventricauda sp. n. 28

Pseudacrobeles mucronatus sp. n. 34

SUBFAMILY ACROBELINAE 41

Genus Acrobeles 42

Acrobeles mariannae 42

Genus Acrobeloides 47

        Acrobeloides glandulatus sp. n. 47

Genus Cervidellus 54

Cervidellus neoalutus sp. n. 54

Cervidellus minutus sp. n. 60

Genus Chiloplacus 66

Chiloplacus aligarhensis sp. n. 66

Genus Nothacrobeles 73

Nothacrobeles punctatus sp.n. 73

Genus Stegellata 80

Stegellata ophioglossa 80

Genus Zeldia 85

Zeldia tridentata 85

SUPERFAMILY PANAGROLAIMOIDEA 90

FAMILY PANAGROLAIMIDAE 90

SUBFAMILY TRICEPHALOBINAE 91

Genus Tricephalobus 91

Tricephalobus quadripapilli sp. n. 92

FAMILY BREVIBUCCIDAE 98

Subfamily Brevibuccinae 98

Genus Brevibucca 98

Brevibucca postamphidia sp. n 99

Genus Plectonchus 105

Plectonchus coptaxii sp. n. 105

SUMMARY 112

PART – B

INTRODUCTION 115

MATERIALS AND METHODS 125

RESULTS 131

DISCUSSION 153

REFERENCES 162

Part – A Taxonomy

Introduction

The nematodes are a successful group of invertebrates placed at a low

level in the taxonomic hierarchy of the animal kingdom. They are the most

diverse phylum, and one of the most diverse of all animals. They have

successfully adapted to nearly every ecological habitat from marine to fresh

water, from the Polar regions to the tropics, as well as the highest to the lowest of

elevations. They are ubiquitous in freshwater, marine, and terrestrial

environments, where they often outnumber other animals in both individual and

species counts, and are found in the locations as diverse as Antarctica and

oceanic trenches. Some of them also can withstand complete dryness on the

surface of rocks. Their size too is extremely variable ranging from less than 100

µm (Greefiella minutum) to greater than 8 metres (Placentonema gigantissima).

The nematodes are the planets most abundant metazoa; of every five animals,

four are nematodes (Platt, 1994; Bongers & Ferris, 1999). They are particularly

abundant in marine, freshwater, and soil habitats. A square yard of woodland or

agricultural habitat may contain several million nematodes. The existence of

nematodes living in water, soil or in parasitizing the plants remained largely

unknown perhaps, because of their exceedingly small size, absence of any

colouration, mostly underground habitat and the difficulties encountered in their

isolation.

The phylum Nematoda is characterized by high species diversity. It has

been estimated that the total number of described and undescribed species might

be ranged from 0.1 to 100 million (May, 1988; Hammond, 1992;

Lambshead,1993; Coomans, 2000). The nematodes are not only numerically

    1 

 

abundant, but they are also very diverse in terms of species. Usually species

richness at a single site is high with an average of 20-60 species per soil sample.

In soil, the nematodes dominate in number as well as species over all

other soil inhabiting animals collectively and have occupied all possible habitats

representing a very wide range of biological diversity. Soil nematode

communities have the potential to provide insights into many soil processes and

functions as most nematodes are active in soil throughout the year (Ritz &

Trudgill, 1999). Nematodes can be used as bioindicators of soil health because

they are ubiquitous and have diverse feeding behaviours and life strategies

(Bongers & Bongers, 1998; Neher, 2001). They occupy several trophic grades

and a central position in the soil food web and play significant roles in biological

processes such as nitrogen cycling and plant growth patterns (Neher, 2001). Soil

nematodes stabilize soil ecosystems, promote substance cycling and energy flow

(Ingham et al., 1985). The ecological classification of terrestrial nematodes have

usually been based on feeding biology (trophic functions) and on life strategies;

colonizers versus persisters (Bongers, 1990). Yeates et al. (1993) classified the

terrestrial nematodes into eight trophic groups viz., plant feeding, hyphal feeding,

substrate ingestion, predation on animals, bacterial feeding, unicellular eukaryote

feeding, dispersal/infective stage of parasites and omnivorous. Free-living

nematodes promote decomposition of soil organic matter, mineralization of plant

nutrients and nutrient cycling, amend soil physico-chemical property and

improve soil fertility (Ferris et al., 2004). Some free living nematodes suppress

bacterial, fungal and nematode diseases (Khan & Kim, 2007).

    2 

 

All terrestrial ecosystems consist of aboveground and belowground

components that interact to influence community- and ecosystem-level processes.

Several recent studies have indicated that biotic interactions in soil can regulate

the structure and functioning of the above ground communities (Wardle et al.,

2004). Soil nematode communities can provide unique insights into many aspects

of soil processes; they can offer a holistic measure of the biotic and functional

status of soils (Ritz & Trudgill, 1999). They are good environmental indicators

because of their strong relationships with land management (Todd, 1996; Neher

and Campbell, 1994; Liang et al., 1999; Fiscus and Neher, 2002) and

aboveground vegetation (Ingham et al., 1985; Bongers and Bongers, 1998;

Bongers and Ferris, 1999; Yeates, 1999).

Measurement of meiofaunal diversity and abundance is an important but

time consuming process. Morphological identification of individual organisms to

named species is often not technically possible due to sheer abundance, small

size, and lack of expert knowledge of the groups encountered. This is especially

true of nematodes, whose diversity in soils and sediments remains essentially

unknown. Surveys of benthic sediments suggest that the total species number for

marine nematodes may exceed 1 million (Lambshead 1993; Lambshead 2001),

with only a few thousand described in the scientific literature (Malakhov 1994;

De Ley & Blaxter 2002). In terrestrial systems, nematode diversity appears to be

under-reported (Lawton et al., 1998), with, for example, only about 200 species

of soil nematodes being described from the British Isles (Boag & Yeates 1998).

The maximum number of nematode taxa described from a single soil site is 228

from a prairie in Kansas, USA (Orr & Dickerson 1966; Boag & Yeates 1998).

    3 

 

Nematodes are arguably the most numerous metazoans in the soil and aquatic

sediments (Lambshead, 2004), the extraordinary species diversity, paucity of

trained taxonomists, labour intensive work for traditional morphological

identification of soil fauna challenges the nematode taxonomy. To develop new

technology for identification, classification, genome relatedness and diversity, in

nematode genepools the technology to be developed will use molecular,

biosystematic, informatic and genetic tools. New approaches are coming in use to

aid species identifications within the context of a classical morphological system.

Currently a shift from the purely phenotypic to using a combination of both

phenotypic and molecular methods is observed (Powers et al., 1997; Powers,

2004). Also, the phylogenetic species concept has gained more support recently

(Adams, 1998, 2002) and ways to extend its theoretical appeal into practicality

have been evaluated (Nadler, 2002).

For years, morphological identification was the only method widely used

to identify nematodes. As our knowledge of nematodes of agronomical

importance increased, it became clear that morphology alone did not reveal the

complete picture of observed pathological differences between populations

within morphologically delimited species. As a result, new methods have been

looked for that can better predict observed pathological behaviors among

populations within species. Numerous molecular techniques have been developed

that are capable of identifying and quantifying nematodes at the species level and

below. Techniques such as isoenzyme pattern analysis, restriction fragment

length polymorphism (RFLP) analysis, random amplified polymorphic DNA

(RAPD) analysis, polymerase chain reaction (PCR), quantitative polymerase

    4 

 

chain reaction (qPCR), and sequencing of diagnostic rDNA regions have all been

used successfully to identify and quantify several agriculturally important plant-

parasitic nematodes. These methods have their own advantages and limitations.

Most of these methods have been widely used in the diagnostics of agriculturally

important nematodes. DNA sequences of marker genes, Denaturing Gradient Gel

Electrophoresis (DGGE) and the more recently developed method of

pyrosequencing are the three methods employed in biodiversity studies of

freeliving forms. Andre et al. (2002) highlighted the need for the development

and consistency of methods in soil faunal monitoring; commenting that molecular

techniques for community analysis are now widely used in soil microbiology and

have greatly expanded our knowledge of soil microbes. Molecular methods

provide an alternative to traditional morphological identification for routine

assessment of described species. Their application has enabled profiling of

environmental samples of soil microbial populations, overcoming the need to

culture and identify bacteria and fungi from complex mixtures (Amann et al.,

1995) and similarly may reduce the taxonomic expertise currently required to

characterise microfaunal communities.

Blaxter et al. (1998) produced the first molecular phylogenetic framework

of the phylum Nematoda. They constructed a database of small subunit (SSU)

sequences from 53 taxa, including 41 new sequences to construct a phylogenetic

tree of nematodes. Sequences were aligned with reference to a secondary-

structure model and on the basis of similarity. They recognise three major clades:

Clade I groups the vertebrate-parasitic order Trichocephalida with the insect-

parasitic Mermithida, plant-parasitic Dorylaimida and free-living Mononchida,

    5 

 

Clade II links the plant-parasitic Triplonchida with the free-living Enoplida &

Monhysterida and clade C+S groups Chromadorida and Secernentea. Within

Secernentea three major clades were identified (clades III, IV and V). Clade III

represents a grouping of vertebrate- and arthropod-parasitic taxa from the orders

Ascaridida, Spirurida, Oxyurida and Rhigonematida. Clade IV a ‘cephalobid’

clade, groups the plant-parasitic orders Tylenchida and Aphelenchida, the

vertebrate-parasitic genus Strongyloides and the entomopathogenic genus

Steinernema with free-living bacteriovores of the rhabditid families Cephalobidae

and Panagrolaimidae. Clade V groups C. elegans and other members of the

suborder Rhabditina with the vertebrate-parasitic order Strongylida, the

entomopathogenic genus Heterorhabditis and the order Diplogasterida. De Ley

and Blaxter (2002, 2004) updated the classification of the phylum Nematoda

using molecular data available from additional species, with morphological data

to assist the placement of taxa for which SSU sequences were not yet available.

They used SSU phylogenies to develop a novel classification reflecting recent

evolutionary findings and proposing the infraorders Cephalobomorpha,

Panagrolaimomorpha and Tylenchomorpha, all within a considerably expanded

suborder Tylenchina.

Nematodes of the suborder Cephalobina Andrassy, 1974 include an

ecologically and morphologically diverse array of species that range from soil

dwelling microbivores to parasites of vertebrates (Strongyloidoidea, including

Strongyloides) and invertebrates [entomopathogens used commercially for

biological control (Steinernema)]. Despite a long history of study, certain of these

microbivores (Cephaloboidea) present some of the most intractable problems in

    6 

 

nematode systematics (De Ley, 1997); the lack of an evolutionary framework for

these taxa has prevented the identification of natural groups and inhibited

understanding of soil biodiversity and nematode ecology.

The Cephaloboidea are a relatively distinctive group of widely distributed

bacterial-feeding soil nematodes, most frequently represented by the family

Cephalobidae, which includes more than 275 nominal species and 24 genera.

These nematodes, which are often striking in their labial morphology, are found

in soils worldwide and are typically the most abundant microbivores in nutrient-

poor soils such as deserts (Freckman and Mankau, 1986) and dry Antarctic

valleys (Freckman and Virginia, 1997). Despite their abundance and

cosmopolitan distribution, cephalobs have been among the most difficult

nematodes to diagnose, identify and classify. Historically these genera have

primarily been recognized based on variation in labial morphology, but molecular

phylogenies show the same general labial (probolae) morphotype often results

from recurrent similarity, a result consistent with the phenotypic plasticity of

probolae for some species in ecological time. The taxonomy, identification and

classification of cephalobs have become more difficult with time. For example,

genera that once seemed discrete based on morphological observations of

relatively few species have been blurred by discovery and description of

additional species with confounding character combinations, or overlaps between

characters previously considered diagnostic (De Ley, 1997). As a result, the

morphological characters originally proposed for distinguishing most genera are

now thought to be of questionable value, as demonstrated for Acrobeloides,

Cephalobus, Chiloplacus, Eucephalobus and Pseudacrobeles (De Ley, 1997).

    7 

 

More potentially disturbing are longstanding reports of substantial intraspecific

variation of lip structures within and between natural and in vitro cultured

populations of certain species of Cephalobidae (Allen and Noffsinger, 1972;

Anderson, 1965, 1968; Anderson and Hooper, 1970), with the range of variation

within single species sometimes exceeding differences used to discriminate

among genera. Addressing these systematic problems by developing a

phylogenetic framework for cephalobs is essential, because investigations of soil

biodiversity and ecology almost invariably require identification of cephalobs,

and taxa from this suborder are increasingly used as model organisms for

comparative developmental studies (Baldwin et al., 1997; Dolinski et al., 2001;

Félix et al., 2000; Goldstein et al., 1998; Schierenberg, 2000). Moreover, a

comprehensive phylogenetic framework for cephalobs has the potential to

provide insights into the evolution of features that may be associated with

nematode parasitism of plants, annelids, insects, and vertebrates.

Proposed phylogenetic affinities of cephalobs have been quite diverse.

For much of the early history of nematode taxonomy, cephalobs were considered

very closely related to rhabditids, the group that includes the premier nematode

model organism Caenorhabditis elegans. Other authors have proposed closer

affinities with certain predominantly parasitic nematodes, most notably with the

fungivorous or phytophagous tylenchs (Siddiqi, 1980), the annelid parasitic

drilonematids (Coomans and Goodey, 1965; De Ley and Coomans, 1990;

Lisetskaya, 1968; Spiridonov et al., 2005), and the entomopathogenic

steinernematids (Poinar, 1993). Regions of 28S rDNA subunit, including the

D2/D3 variable domains, have been used to infer relationships among certain

    8 

 

closely related species, primarily congeners (Baldwin et al., 2001; De Ley et al.,

1999; Nadler et al., 2003; Stock et al., 2001), Molecular phylogenies with

taxonomically broader representation for cephalobs have been inferred using

sequences from SSU (18S) ribosomal DNA (Blaxter et al., 1998; Félix et al.,

2000; Goldstein et al., 1998) and RNA polymerase II genes (Baldwin et al.,

1997). These studies have provided new insights into the relationships of

cephalobs to other major groups of nematodes, including the unexpected Wnding

that Tylenchida and Aphelenchida, which include the most economically

important plant parasites among nematodes, share most recent common ancestry

with cephalobs (Blaxter et al., 1998). A phylogeny of Cephaloboidea also

provides the opportunity to test the monophyly of other genera and examine their

relationships. Molecular phylogenetic trees can further serve as independent

frameworks for the investigation of morphological characters in nematodes

(Baldwin et al., 1997; Nadler & Hudspeth, 1998).

Recently Nadler et al. (2006) studied the phylogeny of Cephalobina. The

phylogenetic analyses of ribosomal (LSU) sequence data from 53 taxa revealed

strong support for monophyly of taxa representing the cephaloboidea, but do not

support the monophyly of most genera within this superfamily. Trees inferred

from LSU sequences, include a large clade containing most (but not all) genera

classically representing cephalobs plus plant parasites from the orders Tylenchida

and Aphelenchida. Published phylogenies inferred from SSU rDNA, although

including far fewer cephalob taxa, also recover this relationship (Blaxter et al.,

1998; Félix et al., 2000). Thus, both SSU and LSU sequence data indicate that

certain plant parasitic species share most recent common ancestry with

    9 

 

cephalobs, contrary to most traditional evolutionary concepts. Although the LSU

trees reveal that a large group of taxa normally classified as cephalobs are

monophyletic, the exclusion of certain genera and the close relationship of some

plant parasites indicates that even newer classification proposals for these taxa

(De Ley and Blaxter, 2002) will require some amendments to reflect these

findings. The LSU trees clearly refute the hypothesis that Macrolaimellus is more

closely related to chambersiellids (represented by Macrolaimus and Fescia in the

LSU trees), and strongly support its inclusion in Cephaloboidea.

Meldal et al. (2007) added SSU rDNA sequences for 100 un-sequenced

species of nematodes, including 46 marine taxa. Sequences for more than 200

taxa have been analysed based on Bayesian inference and logDet-transformed

distances. The phylogenetic analysis provided the support for the re-classification

of secernentea as the order Rhabditida that derived from a common ancestor of

chromadorean orders Araeolaimida, Chromadorida, Desmodorida,

Desmoscolecida and Monhysterida. Their analysis also support the the position of

Bunonema close to the Diplogasteroidea in the Rhabditina. Meldal et al. also

proved that SSU rDNA genes are very effective in the recovery of many

monophyletic group within the phylum Nematoda and provided clarification of

relationships that were uncertain or controversial. However, there were certain

limitations to the use of SSU. The SSU gene did not provide significant support

for the class Chromadoria or clear evidence for the relationship between the three

classes, Enoplia, Dorylaimia, and Chromadoria. Furthermore, across the whole

phylum, the phylogenetically informative characters of the SSU gene are not

informative in a parsimony analysis, highlighting the short-comings of the

    10 

 

parsimony method for large-scale phylogenetic modelling. Recently Abebe et al.

(2011) presented a review of the various techniques used in the taxonomy of free

living and plant parasitic nematodes and critique those methods in the context of

recent developments and trends including their implications in nematode

taxonomy, biodiversity and biogeography.

    11 

 

Historical Background

Although nematology attracted attention and recognition only in 20th

century, our knowledge of a few species of nematodes of medical importance

dates back to Papyrus Ebers (Circa 1500 BC). The intestinal round worm

(Ascaris lumbricoides), filarid (Wucheraria bancrofti) and guinea worm or fiery

serpent of Moses (Dracunculus medinensis) were already known to the ancient

man. However, marine, freshwater, soil and plant nematodes remained little

known groups mainly because of their extremely small size and the difficulties

encountered in their isolation, mounting and observation.

Knowledge of free-living nematodes dates back to 1656 when Borellus

for the first time observed Turbatrix aceti the ‘vinegar eels’. Observations and

descriptions of plant parasitic nematodes, which were less conspicuous to ancient

scientists, didn’t receive as much or as early attention as did animal parasites.

Needham (1743) solved the “riddle of cockle” when he crushed one of the

diseased wheat grains and observed “Aquatic Animals” the first plant parasitic

nematode (Anguina tritici). He found tiny serpent-like worms, which were later

named Vibrio tritici Steinbuch (1799). Muller (1783) described several species of

free-living freshwater nematodes. Nematode taxonomy further developed and

landmark progress was observed in the middle of 19th century. Around 1850,

marine biologists began to recognize nematodes; there were, studies on the

nematodes of Iceland (Leuckart, 1849), the Mediterranean (Eberth, 1863), the

English coast (Bastian, 1865), the coast of Brittany (Villot, 1875) and on

nematodes collected by various expeditions (Von Linstow, 1876). Freshwater

nematodes received further interest around 1890 with the papers of Daday (1897)

on the Hungarian fauna. Dujardin (1845), Bastian (1865), Schneider (1866), de

    12 

 

Man (1884), Daday (1905) and Maupas (1900) were the pioneers of the field.

Early work on the free-living nematodes included careful descriptions of

Enoplus, Oncholaimus, Rhabditis and Dorylaimus (Dujardin, 1845). He was first

to recognize the close relationship of free-living and plant parasitic nematodes.

Bastian (1865), made significant contributions in the field of Nematology. He

grouped the free-living nematodes into soil, fresh water and marine forms and

described 100 new species of 30 genera in which 23 were new to science, in a

single paper. de Man (1876-1927) listed eight families of free-living nematodes.

de Man’s (1884) formula for denoting measurements of nematodes is universally

used in taxonomy till date. Cobb, a contemporary of de Man, is considered, the

Father of Nematology. He placed nematodes under separate Phylum Nemata.

Significant changes in classification were proposed by Cobb (1920), De Coninck

(1965), Maggenti (1963, 70), and by Andrássy (1976, 84). In Chitwood’s (1933,

37) classification, ‘Nematoda’ was treated as a phylum with two classes,

‘Phasmidia’ and ‘Aphasmidia’, based on presence or absence of phasmids. The

terms Secernentea and Adenophorea were introduced by Chitwood (1958) who

proposed the system of classification of nematodes including free-living and

parasitic nematodes. Andrássy has contributed extensively to the taxonomy of

major groups of terrestrial and freshwater nematodes. In his productive career he

described more than 500 taxa of nematodes and at least 39 taxa were named after

him. Besides his voluminous contributions to nematode taxonomy and

systematics, he has had an enormous influence on soil and nematode ecology. He

published keys for identification, proposed and raised higher taxa, amended and

put forth classification schemes besides authoring valuable books including the

    13 

 

extremely useful compilation, ‘Klasse Nematoda' (1984) based on the diagnosis

of orders of Araeolaimida, Enoplida, Chromadorida, Monhysterida, and

Rhabditida and their subordinate taxa. This book exercised major influence on

the direction of nematode ecology in that it bridged the gap between nematode

taxonomy and soil ecology.

Order Rhabditida was erected by Chitwood (1933) for bacteriophagus

rhabditids. Dujardin (1845) first established the genus Rhabditis with Rhabditis

terricola as its type species. However it was not clearly defined until more than

one hundred year later (Dougherty, 1955). Örley (1880) proposed a family

Rhabditidae, for the genera Anguillula, Cephalobus, Oxyuris, Rhabditis and

Teratocephalus. He placed this family in the higher category “Rhabditi formae”

which formed a connecting link between free living and animal parasitic

nematodes. Micoletzky (1922) described seven species. His system was,

however, rather artificial in that he united all nematodes having a prismatic,

unarmed stoma under the family Rhabditidae, viz. the subfamilies

Cylindrolaiminae, Plectinae, Rhabditinae and Bunonematinae. The subfamily

Rhabditinae was itself heterogenous, and composed of the following genera:

Rhabditis, Diploscapter, Cephalobus, Chambersiella, Teratocephalus and

Rhodolaimus.

The record of cephalobid nematode can be traced back to 1656 when

Borellus observed “vinegar eels” for the first time. Muller (1783) named these

eels as Vibrio aceti, later on it was redescribed and shuffled to various taxa by

several authors, finally Peters (1927) proposed the genus Turbatrix and accepted

T. aceti as its type species. Though the first cephalob species “Cephalobus

    14 

 

persegnis” was formally described in 1865 by Bastian, it was not until the work

of Cobb (1924) and Thorne (1925, 1937) that basic taxonomic concepts and

terminology were established. Cobb (1924) rehabilitated the genus Acrobeles von

Linstow, 1877 and suggested the subgenera Acrobeles and Acrobeloides. Thorne

(1925) accepted the subgenera proposed by Cobb and produced a detailed

account on morphology, systematics and taxonomy of the genus Acrobeles. He

described thirty new species of Acrobeles and grouped them under two

subgenera. Thorne’s (1937) revision of the Cephalobidae has been of immense

value and importance. He (l.c) proposed subfamily Acrobelinae for genera

Placodira, Chiloplacus, Cervidellus and Zeldia and redescribed the genus

Acrobeloides. He also proposed superfamily Panagrolaimoidea with family

Panagrolaimidae and subfamily Panagrolaiminae. Later on he (1938, 39)

described the genera Panagrobelus and Panagrellus under Panagrolaiminae and

Stegellata under Acrobelinae. Simultaneously, Steiner (1934, 36, 38) proposed

the genus Procephalobus under the family Panagrolaimidae, and in Cephalobidae

the genera Eucephalobus, Tricephalobus and Pseudacrobeles were proposed.

Andrássy (1967) published detailed information on Cephalobinae

Filipjev, 1934. In 1974, he proposed the Suborder Cephalobina, to include an

incredibly diverse array of free-living microbivores. He included three

superfamilies Cephaloboidea Filipjev, 1934, Elaphonematoidea Heyns, 1962 and

Panagrolaimoidea Thorne, 1937 under Cephalobina. In Cephaloboidea he erected

the family Metacrobelidae and placed Metacrobeles Loof, 1962 under it. Further,

in 1984, he added two more superfamilies viz. Drilonematoidea Peirantoni, 1916

and Myolaimoidea Andrassy, 1958 under Cephalobina and accepted eight

    15 

 

families and ten subfamilies in these five superfamilies. He also proposed five

new genera Acrobelophis, Ypsylonellus, Stegelletina, Panagrocephalus and

Panagrobelium. Several other scientists who contributed to morphology and

taxonomy of cephalobids were Fuchs (1930), Filipjev (1934), Timm (1956, 60,

71), Brezeski (1960) and Loof (1962) who added few more genera and species to

the group.

Heyns (1962) published a series of papers on cephalobids and proposed a

superfamily Elaphonematoidea with family Elaphonematidae for the genus

Elaphonema. He also proposed family Osstellidae with subfamily Osstellinae for

the genus Osstella. In 1968 he described a genus Paracrobeles. Nesterov (1970)

proposed a genus Acromoldavicus and redescribed Acrobeloides skrjabini. Allen

and Noffsinger (1971, 72) revised the genus Zeldia and added few species

besides an identification key. They also proposed a new genus Nothacrobeles

under Acrobelinae and described four new species viz. N. sheri, N. lepidus, N.

maximus and N. subtilus and transferred Zeldia acrobeles to Nothacrobeles

acrobeles as a new combination.

Boström (1984-2000) worked extensively on the taxonomy of

cephalobids. He (1984a, b) described morphological variability of Chiloplacus

minimus and compared the morphological features of three species of

Eucephalobus viz., E. striatus, E. oxyuroides and E. mucronatus by light and

scanning electron microscopy. In 1985, he described four new species viz.

Acrobeles oosiensis, Zeldia brevicauda, Cervidellus neftasiensis, C. serratus,

redescribed Acrobeloides emarginatus (de Man, 1880) Thorne, 1937 and

proposed a new genus Acrolobus. He (1988a, b) further described Cervidellus

    16 

 

spitzbergensis, Acrobelophis minimus, Acrobeloides tricornis, Eucephalobus

articus and conducted the morphological and systematic studies to investigate the

structure and function of labial probolae of the family Cephalobidae. In 1989, he

gave description of three populations of Pangrolaimus viz. P. superbus, P.

rigidus and P. detritophagus. He (1990, `91, `92) reported Heterocephalobellus

putamiensis, Seleborca complexa, Zeldia punctata, Acrobeloides ciliatus and

Cervidellus serratus from the soil samples from Greece. Boström (1993a, b)

described Cephalobus persegnis and Eucephalobus striatus from Ireland and E.

hooperi and Acrobeloides nanus from Malaysia. He (1995) described

Panagrolaimus magnivulvatus from Antarctica and in 2000, he reported a

divergent population of Cervidellus capraeolus (De Ley, Geraert & Coomans,

1990) Boström & De Ley, 1996 from Bahamas.

Rashid, Geraert & Sharma (1984) also contributed to Cephalobina by

working on their morphology, taxonomy and systematics. They proposed two

new genera Cephalonema and Heterocephalobellus with C. longicauda and H.

brasilensis as their type respectively under the family Cephalobidae. They

described two new species viz. Heterocephalobus tabacum and Cephalobus

pseudoparvus and also proposed three synonyms: Acrobeles capensis as a junior

synonym of A. mariannae, the genus Pseudocephalobus as a synonym of

Teratolobus and the family Alirhabditidae as a synonym of the Cephalobidae.

Rashid et al. (1989) synonymized Acrobelinae with Cephalobinae mainly on the

basis of presence or absence of labial probolae and indentations of the head

border.

    17 

 

De Ley et al. (1990-97) added a good number of species besides

publishing revision of genera and also revised the terminology of stoma

components by studying the ultrastructure of the stoma in Cephalobidae,

Panagrolaimidae and Rhabditidae. Siddiqi (1993) proposed five new genera and

eight new species of Cephalobina. He (2002) also described a new genus

Catoralaimellus with C. cornutus as its type and two new species of

Macrolaimellus viz., M. crassus and M. filumicus. Velde et al. (1994) elucidated

the ultrastructure of buccal cavity and cuticle in three species of cephalobs.

Morphology, oviposition and embryogenesis of Acrobeloides nanus was studied

by Bird et al. (1994). Vinciguerra (1994) reported new genus Metacrolobus

festonatus. Vinciguerra and Clausi (1996) reported two new species of

Acrobelophis viz. A. lanceolatus and A. fuegensis from soil in Argentina. A new

genus Penjatinema was described and morphology of P. natalense was discussed

by Heyns and Swart (1998). Clausi (1998) reported Cervidellus vinciguerrae

sp.n. from the soil samples around the moss plants in Argentina. Karegar et al.

(1998) described one new and one known species of Stegelletina and three

species of Cervidellus. Holovachov et al. (2001) described a new genus

Acroukrainicus with A. sagittiferus as its type species. Further, Holovachov &

Boström (2006) proposed two new genera viz. Panagrolobus and Deleyia under

subfamily Cephalobinae and described three species P. vanmegenae, D. poinari

and D. aspiculata. Abolafia and Peña-Santiago (2002, 2003, 2006, 2009) added

several new species to various genera and revised the genera, Acrobeloides,

Chiloplacus, Pseudacrobeles, Nothacrobeles, Panagrolaimus, Cephalobus and

also provided keys to species identification.

    18 

 

Nematode problems of various kinds must have existed since time

immemorial. In India work on Nematology has been started as one of the

disciplines of agricultural sciences. Barber (1901) was the first to record the

infestation of root-knot nematode on tea in South India. During the period 1901-

1958 there had been very little progress, though there were historical breaking

discoveries (Barber, 1901; Butler, 1906, 1913, 1919; Ayyar, 1926, 1933; Dastur,

1936). Brief historical perspectives of the growth and development of

nematology in India have been reported by various authors in the past (Swarup et

al., 1967; Seshadri, 1965; Swarup and Seshadri, 1974).

Organized research on plant nematodes started only after the end of 1950.

The 1960s could be regarded as the most active phase for the growth of

nematology in general and nematode taxonomy in particular in India. Primarily,

nematological research in India has focussed more on the plant parasitic and

animal parasitic groups. Little work has been done on the free-living group-

Rhabditida, probably because they have no direct concern with agriculture and

livestock. Only a few scientists have worked on this heterogenous group during

the late 60s and 70s. One of the earliest reports was the description of Tridontus

longicaudatus Khera, 1965. Khera (1969) described Mesodiplogasteroides,

Operculorhabditis, Saprorhabditis and Praeputirhabditis and in 1970 he further

described two new genera viz. Paradoxogaster and Gobindonema. Later in 1971

he described Paradoxorhabditis in the subfamily protorhabditinae. Suryawanshi

(1971) described Tawdenema and Syedella which later on synonimized with

Acrostichus and Pareudiplogaster respectively. Jairajpuri et al. (1973)

redescribed Tridontus longicaudatus (Mononchoides longicaudatus) and

    19 

 

    20 

 

synonymised Syedella with Tridontus. Tahseen et al. (2005) and Ahmad et al.

(2007) described the new genera Metarhabditis and Sclerorhabditis respectively.

Recently, Ahmad et al. (2010), Mahamood & Ahmad (2009) added new species

under the genera Mesorhabditis, Diplogasteroides and Rhabditidoides

Similarly the studies on the taxonomy of cephalobid nematodes has not

been carried out extensively. Khera (1968), described the genus Acrobelinema (=

Chiloplacus) with A. cornis as its type species. Suryawanshi (1971) proposed the

genus Alirhabditis and erected the subfamily Alirhabditinae for this genus. Joshi

(1972) reported a new genus Pseudocephalobus (= Teratolobus) from

Marathwada. Ali et al. (1973) described two new species of Drilocephalobus and

proposed a new family Drilocephalobidae with a revised classification of the

superfamily Cephaloboidea. Rathore and Nama (1992) described two new

species viz. Acrobeloides conoidis and Chiloplacus jodhpurensis from Jodhpur..

Recently, Tahseen et al. (1999) made the morphometrical observations on the

populations belonging to subfamily Acrobelinae viz. Zeldia punctata,

Chiloplacus subtenius and Seleborca complexa through scanning electron

microscopy.

The present work has been divided into two parts. Part A deals with the

taxonomy and biodiversity of free living nematodes. The nematodes of suborder

Cephalobina have been described in this part. Cephalobids are typically the most

diverse and abundant microbivores found in the soils world wide. This group is

interesting because they were equally abundant in both type of habitats studied

(i.e. crop fields and wastelands) during present work. In India the work on the

taxonomy of this group has not been carried out extensively, so in the present

work the taxonomy is restricted to the nematodes of suborder Cephalobina. A

total of ten new and three already known species have been described and

illustrated. In Part B ecological aspects like nematode community structure and

ecological indices, in two different types of habitats (i.e. crop field and wasteland)

have been analysed and compared. Different indices have been calculated for

diversity and food web studies.

 

20a  

Materials &

Methods

Sampling: Samples for cephalobid nematodes were collected from agricultural

fields, wastelands, soil samples rich in organic debris, decayed and decaying

plant parts and farmyard manure from different parts of the country, especially

from Aligarh district and Eastern and Western Ghats of India. Some samples

from older collections were also screened. The samples were collected at regular

period throughout the year. The soil samples were taken from a depth of 10-20

cm and kept in airtight polythene bags. All relevant information such as host,

locality and date of collection were marked on the samples and these samples

were then brought to the laboratory for further processing.

Processing of soil samples: Samples were processed by modified Cobb’s (1918)

sieving and decantation and modified Baermann’s funnel techniques. From each

large sample, a sub-sample of about 500 cc was taken and mixed thoroughly with

water in a bucket taking care to remove debris and break the large clods and soil

crumbs. The bucket was then filled with water and the suspension was stirred to

make it homogenous. The mixture was kept undisturbed for about half a minute

so as to allow heavy matter to settle down to bottom of bucket. The suspension

was then passed into another bucket through a coarse sieve (2 mm pore size)

which retained large debris, roots and leaves etc. The suspension in the second

bucket was stirred thoroughly and was kept undisturbed for 30 seconds and then

poured through a fine sieve of mesh number 300 (pore size 53 µm). Nematodes

and very fine soil particles were retained on the sieve, the residue was then

collected in a beaker. This step was repeated 2 to 3 times for good recovery of

nematodes.

    21 

 

Isolation of nematodes: The residue collected in the beaker was poured on a

small coarse sieve lined with tissue paper. This sieve was then placed on a

Baermann’s funnel containing water sufficient to touch the bottom of the sieve.

Special care was taken to avoid trapping air bubbles at the bottom of the sieve.

The stem of the funnel was fitted with a rubber tubing provided with a stopper.

The nematodes migrated from the sieve into the clear water of the funnel and

accumulated at the bottom. After 24 hours, a small amount of water was drained

into a cavity block through the rubber tubing. The nematodes thus isolated were

fixed and processed for mounting on slides.

Killing and fixation: The collected nematodes in cavity blocks were left

undisturbed for a few minutes so as to allow them to settle down at the bottom.

Excess water was removed using a fine dropper and the hot FA fixative (8 ml of

40% commercial formaldehyde + 2 ml of glycerol + 90 ml of distilled water) was

poured into the cavity block. This act simultaneously killed and fixed the

nematodes.

Mounting and sealing: 24 hours after fixation, the nematodes were transferred

to a mixture of glycerine-alcohol (5 parts glycerine + 95 parts 30% alcohol) in a

cavity block, which was then in a desiccator containing anhydrous calcium

chloride. After 3 to 4 weeks the nematodes were dehydrated and were ready to be

mounted. A small drop of anhydrous glycerine was placed on a clean glass slide

and the nematodes were transferred from the cavity block into this drop. Either a

ring of wax was made or the pieces of wax were kept around the drop and a

    22 

 

circular glass cover slip was gently placed on the ring or pieces. This slide was

then heated on a hot plate. As the wax melted it sealed the drop of glycerine with

the nematodes.

Measurements and drawings: Measurements were made on specimens

mounted in dehydrated glycerine with an ocular micrometer. De Man’s (1884)

formula was used to denote the dimensions of nematodes. All morphological

observations, drawings and photographs were made on Olympus BX 50 and

Nikon 80i DIC microscopes.

Abbreviations used in the text

L = Total body length

a = Body length / greatest body diameter

b = Body length / distance from anterior end to the oesophago-intestinal junction

c = Body length / tail length

c´ = Tail length / anal body diameter

V = Distance of vulva from anterior end x 100 / body length

ABD = Anal body diameter

VBD = Vulval body diameter

Diam. = Diameter/diameters

    23 

 

Systematics

Order Rhabditida Chitwood, 1933

Diagnosis: Cuticle usually annulated, rarely ornamented with longitudinal striae

or punctations. Labial region mostly continuous, lips separate, three or six, often

with projections. Amphids small, inconspicuous, on lateral lips, exceptionally

large and more posterior in position. Mouth cavity of two main types: tuboid or

more or less spacious; in former case unarmed or possessing minute denticles, in

latter case usually provided with well developed teeth. Pharynx with either

median or terminal valvular bulb. Excretory pore visible. Intestine with wide

lumen. Three rectal glands generally present. Female reproductive system

didelphic or mono-prodelphic, in latter case generally with posterior uterine sac.

Ovaries reflexed. Ovi- or viviparous. Spicules ocassionaly fused. Male either

with paired genital papillae or with caudal bursa possessing paired rod like

papillae or ribs. Tail often different in each sex, without caudal; glands or

spinneret, but with distinct phasmids.

Type suborder: Rhabditina Chitwood, 1933

Other suborders: Cephalobina Andrassy, 1974

Diplogastrina Micoletzky, 1922

Myolaimina Inglis, 1983

Teratocephalina Andrassy, 1974

Suborder Cephalobina Andrassy, 1974

Diagnosis: Lips three or six, mostly separate; labial region often bearing

projections (probolae) of very various appearances. Amphids minute, pore-like,

on lateral lips. Mouth cavity tuboid, composed of six rings: cheilo-, gymno-, pro-,

    24 

 

meso-, meta- and telostom. The four latter (= stegostom) surrounded by

pharyngeal collar. Dorsal wall of metastom with a minute tooth-like projection.

Corpus and isthmus of pharynx well separated, terminal bulb possessing a well

developed grinder. Excretory pore distinct. Female genital system organ always

unpaired, prevulval, but ovary reflexed beyond the vulva. Spermatheca generally

present at anterior flexure of gonad. Predominantly oviparous. Spicules simple,

never fused, gubernaculum present. Male supplements papilloid, arranged in

pairs. No bursa. Tail generally short. Phasmids well discernible.

Type Superfamily: Cephaloboidea Filipjev, 1934

Other Superfamilies: Chambersielloidea Thorne, 1937

Panagrolaimoidea Thorne, 1937

Superfamily Cephaloboidea Filipjev, 1934

Diagnosis: Lip region varies from simple amalgamated type to those having

elaborate modified structures. Stoma quite narrow with uniformly sclerotized ring

elements, divided into three distinct sections, with or without metastomal tooth.

Oesophagus with or without grinders apparatus in the basal bulb. Female gonad

mono-prodelphic, reflexed, ovary extending beyond vulva, postvulval part in

most cases showing double flexures; spermatheca invariably present at anterior

flexure of gonad. Testis single, with reflexed terminal part. Spicules ventrally

curved with velum and capitulum. Gubernaculum present. Bursa absent. Genital

papillae present or absent.

Type family: Cephalobidae Filipjev, 1934

Other families: Elaphonematidae Heyns, 1962

Osstellidae Heyns, 1962

    25 

 

Family Cephalobidae Filipjev, 1934

Diagnosis: Cuticle annulated with sharply bordered lateral fields, occassionally

divided by longitudinal lines. Three cephalic probolae and three or six labial

probolae often present. Amphids located on lateral lips. Mouth cavity tuboid,

generally very narrow, ring elements small, uniformly sclerotized except for the

mostly unsclerotized gymnostom; cheilostom wider than the other rings. Dorsal

wall of metastom with minute tooth like projection. Pharynx consisting of usual

three sections, bulb strong. Vulval opening at two-thirds of body length, ovary

reflexed far posterior to vulva, its postvulval section in almost every case with

double flexures. Post-uterine sac present, generally short, rarely absent. Males in

general nearly as frequent as females. Phasmids distinct.

Type subfamily: Cephalobinae Filipjev, 1934

Other subfamilies: Acrobelinae Thorne, 1937

Acrolobinae De Ley, Siddiqi and Boström, 1993

Metacrobelinae Andrássy, 1974

Subfamily Cephalobinae Filipjev, 1934

Diagnosis: Lip region with simple cephalic and labial probolae, mostly

hexaradiate in symmetry, no deep clefts between lips. Cheilostom a broad

chamber, gymnostom short, dorsal metastegostom with a small tooth. Pharyngeal

corpus cylindrical, basal bulb with well developed grinder. Nerve ring usually

surrounding the base of corpus anterior to the isthmus. Female gonad single,

reflexed, ovary extending beyond vulva; spermatheca present at anterior flexure

of gonad. Males without bursa. Genital papillae present.

    26 

 

Type genus: Cephalobus Bastian, 1865

Other genera: Bunobus De Ley, Siddiqi & Boström, 1993

Eucephalobus Steiner, 1936

Heterocephalobellus Rashid, Geraert & Sharma, 1985

Heterocephalobus (Brzeski, 1960) Brzeski, 1961

Pseudacrobeles Steiner, 1938

Genus Pseudacrobeles Steiner, 1938

Diagnosis: Lateral fields with three incisures, fading out at or near the phasmids.

Lip region with hexaradiate, triradiate or bilateral symmetry and bearing 6+4

papilliform sensillae. Amphids small slits or oval pores at bases of lateral lips.

Lips separate or amalgamated; lateral lips may be reduced. Cephalic probolae

absent to short-setiform. Labial probolae absent to low knobs or ridges. Radial

ridges absent, tangential ridges present or absent. Mouth opening circular to

triangular, occasionally with small radial striae separating small liplet-like

structures but never extending deeply between the lips. Stoma with six sets of

sclerotizations. Cheilorhabdions comma-, bar- or granule- shaped in optical

section; cheilostom wide. Appearance of gymnostom in lateral view varying

from being as wide as cheilostom and having sclerotized rhabdia, to being as

narrow as stegostom and having inconspicuous rhabdia. Stegostom sections

clearly narrower than cheilostom. Females with post-uterine branch usually

developed, never surpassing ovary tip. Female tail sharp or blunt, conical, from

2.5 to 10 anal body diam. long. Male tail with or without mucro, with or without

    27 

 

extension of the body core beyond the posteriormost papillae. Gubernaculum

with cornua crurum never prominent.

Pseudacrobeles ventricauda sp. n.

(Fig. 1, 2)

Measurements: In Table 1.

Females: Body slender, slightly ventrally curved upon fixation, tapering

gradually towards both the ends. Cuticle transversely annulated, annules 1.4-2.0

µm wide at midbody. Lateral fields with three incisures, usually indistinct. Lips

separated, lip region with 6+4 papillae. Cephalic probolae setiform. Labial

probolae present, low. Stoma cephaloboid. Cheilostom with bar-shaped rhabdia;

gymnostom intermediate between cheilostom and stegostom in width and degree

of sclerotization. Stegostom narrow with weakly sclerotized rhabdia,

metastegostom with a minute dorsal tooth . Pharyngeal corpus cylindrical, 4.5-5.5

times isthmus length. Isthmus visibly demarcated from corpus by transverse

markings. Basal bulb pyriform, with grinders. Nerve ring surrounding the

posterior part of the corpus, at 65-70% of neck length. Excretory pore opposite

nerve ring, at 66-71% of neck length. Hemizonid and excretory pore are at the

same level. Intestine with distinct wide lumen. Cardia conoid, enveloped by

intestinal tissue.

Reproductive system mono-prodelphic. Ovary reversed, on right side of

intestine, with a double flexure or sometimes without any flexure posterior to

vulva. Oocytes arranged in one or more rows in the germinal zone and in single

or double row in maturation zone. Oviduct short. Spermatheca well developed

1.3 – 2.6 times corresponding body diam. long, containing spermatozoa. Uterus

    28 

 

well developed about 2-3 times the corresponding body diam. long, sometimes

with single ova in the lumen. Post-uterine sac 1.2-1.8 times the corresponding

body diam. long. Vagina thick-walled, 0.25-0.33 times the vulval body diam. Tail

elongate-conoid gradually tapering to a sharply pointed tip. A small subterminal

ventral projection is also present near the tail tip.

Males: General appearance similar to that of females. Habitus ventrally curved,

more in the posterior region. Reproductive system monorchic. Testis with

anterior ventral flexure on right side of intestine. Tail conical bearing an acute

mucro. Genital papillae eight pairs; two pairs precloacal (subventral), one

adcloacal (subventral) and five pairs postcloacal. Of the five postcloacal pairs,

two pairs (one subventral and one lateral) are anterior to phasmid, one subdorsal

pair posterior to phasmid and two subventral pairs near the tail terminus. Spicules

with rounded manubrium, slightly arcuate lamina and rounded tip. Gubernaculum

with well developed crura.

Type habitat and locality: Sandy soil collected from a grass bed near a river close

to the Rushikonda beach, Vishakapatnam.

Type specimens

Holotype female on slide Pseudacrobeles ventricauda sp. n./1; ten

females and ten males (paratypes) on slides Pseudacrobeles ventricauda sp. n./2-

8 deposited in the nematode collection of Department of Zoology, Aligarh

Muslim University, Aligarh.

Diagnosis and relationship

Pseudacrobeles ventricauda sp. n. is characterized by setiform cephalic

probolae, Cheilostom with bar-shaped rhabdia. Post-uterine sac 1.2-1.8 times the

    29 

 

corresponding body diam. long. Vagina thick walled, 0.25-0.35 times the vulval

body diam. Female tail elongate-conoid, with a small subterminal ventral

projection and acute tail terminus. Male tail conical, with fine terminal mucro.

The new species resembles Pseudacrobeles variabilis (Steiner, 1936)

Steiner, 1938 in general morphological characters and body size but differs from

it in having relatively longer post-uterine branch (36-47 µm vs 16-35 µm),

smaller c´ value in females (3.7-4.4 vs 4.6-7.2) and in the shape of female tail

(tail with a sub-terminal ventral projection vs tail terminus straight). The new

species also resembles P. tabacum (Rashid, Geraert & Sharma, 1985) De Ley,

Siddiqi & Boström, 1993 in morphological details. However, the new species

differs from P. tabacum in having comparatively longer pharynx in males (134-

156 µm vs 115-133 µm long), slightly smaller b-value both in males and females

(3.5-4.0 vs 4.0-4.5 in males and 3.4-4.1 vs 4.2-5.0 in females), longer post-uterine

branch 36-47 µm vs 22-31 µm), in the shape of female tail (tail terminus with a

ventral projection vs tail terminus without projection) and slightly smaller

spicules (19-21 µm vs 21-25 µm).

    30 

 

Table 1: Measurements (in µm) of Pseudacrobeles ventricauda sp. n. Mean and S.D. given in parenthesis

Characters Holotype

female Paratype females

(n= 10) Paratype males

(n= 10)

L 608 530-620 (587±27) 501-601 (556±34)

a 22.5 21.5-24.0 (22.8±0.8) 21.9-27.6 (24.7±1.5)

b 3.8 3.4-4.1(3.8±0.2) 3.5-4.0 (3.8±0.2)

c 8.5 7.8-8.8 (8.3±0.3) 12.6-14.5 (13.3±0.5)

c′ 4 3.7-4.4 (4.2±0.2) 2.0-2.4 (2.2±0.1)

V 59.5 57.5-60.5 (59±1.0) --

Maximum body width 26.5 23.5-27.5 (25.5±1.5) 20-25 (22.5±1.5)

Lip width 7 6-7 (6.7±0.4) 6-7 (6±0.3)

Lip height 4 3-4 (3.9±0.3) 3-4 (3.5±0.5)

Length of stoma 13 10-14 (12.5±1.0) 12-13 (12.3±0.5)

Corpus 117 99-123 (113±7) 95-115 (105±5)

Isthmus 23 20.5-26.5 (24.0±2.0) 18.0-27.5 (23.5±3.0)

Basal bulb length 21 18-22 (20±1) 18-19 (18.5±0.5)

Pharynx 159 138-166 (155±8) 133-156 (147±8)

Excretory pore from ant. end 106 96-114 (106±5) 94-108 (102±4.5)

Nerve ring from ant. end 106 96-112 (104±5) 89-106 (98.5±5.0)

Dierid from ant. end 124 121.5-133.5 (128±4) 112-126 (119.5±5.0)

Cardia 4 4-5 (4.5±0.5) 4.0

Basal bulb width 16 15-17 (15.5±0.5) 13-14 (13.1±0.4)

Anterior sac (Spermatheca) 35 32.5-67.5 (46.5±11.5) --

Genital branch 62 62.5-86.0 (76.0±6.5) --

Post-uterine branch 45 36-47 (40.5±4.0) --

VBD 27 23.5-28.5 (26.5±1.5) --

Vulva- anus distance 175 155-189(171±10) --

Rectum/cloaca 20 20-22 (21.0±0.5) 18-21 (19±1.0)

Tail 71 64.5-76.0 (70.5±3.5) 37.5-44.5 (42±2.0)

ABD 18 15-19 (17±1) 18-20 (18.5±1.0)

Phasmids from anus 18 16-21 (19.0±1.5) 17-22 (19.05±1.5)

Testis -- -- 224-295 (256±23)

Spicules -- -- 19-21 (20±0.5)

Gubernaculum -- -- 11-13 (12±0.5)

    31 

 

A

Fig. 2. Pseudacrobeles ventricauda sp. n. A. Anterior region showing stoma, B. Anterior region showing probolae, C. Spermatheca, D. Post-uterine sac, E. Female posterior region, F. Female tail terminus showing ventral projection, G. Spicules and gubernaculum, H. Male posterior region (Scale bars = 20µm).

33

B D

GC

E F H

Pseudacrobeles mucronatus sp. n.

(Fig. 3, 4)

Measurements: In Table 2.

Females: Body slightly ventrally curved after fixation. Cuticle about 1.0-1.5 µm

thick at mid body, with transverse annules. Annules about 1.7-2.2 µm wide at

mid body. Lateral fields occupying 14-22% of mid body diam., with three

incisures. Lip region with triradiate symmetry. Cephalic probolae varying from

distinctly setiform to completely absent. Labial probolae varying from small but

distinct knobs, to flat ridges formed by partially fused lips. Stoma cephaloboid,

cheilorhabdia bar shaped. Gymnostom intermediate between cheilostom and

stegostom in width and degree of sclerotization. Stegostom with distinguished

rhabdia, dorsal metarhabdion with a small tooth like projection. Pharyngeal

corpus cylindrical, 4.8-7.5 times isthmus length. Isthmus short 16.0-22.5 µm

long, Basal bulb pyriform, with well developed valves. Nerve ring lying in the

corpus region, at 57-78% of pharynx length. Excretory pore at the level, or upto

five annules posterior to the trailing edge of nerve ring. Dierid 4-7 annules

posterior to excretory pore. Cardia short, conoid surrounded by intestinal tissue.

Reproductive system mono-prodelphic, ovary directed posteriorly, with

oocytes generally arranged in one or two rows in the germinal zone and in a

single row in maturation zone. Oviduct short. Spermatheca well developed 0.5-

1.5 times corresponding body diam long. Uterus tubular, differentiated into

anterior glandular part, and posterior muscular part with distinct lumen. Post-

uterine sac 0.8-1.3 vulval body diam. long. Vagina thick walled. Vulva transverse

    34 

 

slit like. Rectum 1.2-1.6 anal body diam. long. Tail elongate conoid, 3.5-4.5 anal

body diam. long, with acute terminus. Phasmid at 23-34% of tail length.

Males: Anterior region of males similar to that of females. Variability in the lip

region is also in concurrence with females. Habitus ventrally curved, more in the

posterior region giving it a ‘J’ shaped appearance. Reproductive system

monorchic. Testis ventrally reflexed anteriorly, with flexure on right side of

intestine. Tail conoid with mucronate tip. Mucro either small (with blunt tip) or

long (with pointed tip). Genital papillae eight pairs; two pairs precloacal

(subventral), one adcloacal (subventral) and five pairs postcloacal. Of the five

postcloacal pairs, two pairs (one subventral and one lateral) are anterior to

phasmid, one dorsal pair posterior to phasmid and two subventral pairs near the

tail terminus. Spicules cephaloboid, rounded manubrium, calamus slightly

narrower than manubrium, lamina ventrally curved, with acute terminus.

Gubernaculum with well developed crura.

Type habitat and locality: Decaying organic matter and leaf litter collected from

Indira Gandhi Zoological Park, Vishakapatnam, Andhra Pradesh, India.

Type specimens

Holotype female on slide Pseudacrobeles mucronatus sp. n./1; nine

females and six males (paratypes) on slides Pseudacrobeles mucronatus sp. n. /2-

6, deposited in the nematode collection of Department of Zoology, Aligarh

Muslim University, Aligarh.

Diagnosis and relationship

Pseudacrobeles mucronatus sp. n. is characterized by three incisures in

lateral fields. Cephalic probolae varying from distinctly setiform to completely

    35 

 

absent. Labial probolae varying from small but distinct knobs to flat ridges.

Cheilorhabdia bar shaped. Gymnostom intermediate between cheilostom and

metastegostom in width and degree of sclerotization. Pharyngeal corpus

cylindrical, 4.8-7.5 times isthmus length. Males with mucronate tail tip. Mucro

either small (with blunt tip) or long (with pointed tip). Gubernaculum with well

developed crura.

The new species closely resembles Pseudacrobeles variabilis (Steiner,

1936) Steiner, 1938 in general morphological characters and body size. However,

new species differs from it in having smaller c´ value in females (3.6-4.5 vs 4.8-

7.2), larger corpus to isthmus ratio (4.8-7.5 vs 3.1-4.5 in females and 5.7-6.4 vs

3.1-4.2 in males) and slightly longer gubernaculum (12-14 µm vs 10-12 µm). The

new species also resembles P. baloghi Andrassy, 1968 in body size, shape of lip

region and morphometric values. However, the present species differs from P.

baloghi in having longer body in males (0.52-0.58 mm vs 0.4-0.51), smaller c´

value (2.0-2.4 vs 2.8-3.7), larger corpus to isthmus ratio (4.8-7.5 vs 2.9-4.2 in

females and 5.7-6.4 vs 3.2-4.0 in males), more posterior position of phasmid in

males (20-24 vs 13-19), in shape of male tail (mucronate tail tip vs tail tip with

body core extending in spike for 4-11µm) and slightly longer gubernaculum (12-

14 vs 10-12).

P. mucronatus sp. n. closely resembles P. tabacum Rashid et al., 1985 in

general morphometrics and morphology. However, differences were traced in the

shape of cheilostom (never in granular form vs bar to granule form), longer

pharynx in males (150-163 vs 115-131), smaller b value (3.2-4.0 vs 4.2-5.0 in

females and 3.3-3.6 vs 4.0-4.6 in males), position of nerve ring in females (57-72

    36 

 

% vs 73-74 % of the pharynx length), larger corpus to isthmus ratio in males (5.7-

6.4 vs 4.1-4.7). The new species also resembles P. laevis Thorne, 1937 in body

size, structure of cephalic and labial probolae and other morphological details.

However, differences were found in ‘a’ value (20.7-23.5 vs 24-28 in females and

19.5-23.8 vs 25-29 in males), ‘c’ value of females (8.3-10.0 vs 11-14) and

corpus:isthmus ratio (4.8-7.5 vs 3.3-4.5 in females and 5.7-6.4 vs 3.2-4.1 in

males).

    37 

 

Table 2: Measurements (in µm) of Pseudacrobeles mucronatus sp. n. Mean and S.D. given in parenthesis

Characters Holotype

female Paratype females

(n= 9) Paratype males

(n= 6)

L 534 492-640 (558±41) 518-583 (538±22)

a 20.7 20.7-23.5 (22.1±1.0) 19.5-23.8 (21.6±1.4)

b 3.5 3.2-4.0(3.8±0.2) 3.3-3.6 (3.4±0.1)

c 9.6 8.3-10.0 (9.4±0.7) 12.0-13.2 (12.7±0.4)

c′ 3.7 3.6-4.5 (4.0±0.3) 2.0-2.4 (2.2±0.1)

V 65.5 61.5-65.5 (63.5±1.5) --

Maximum body width 25.5 21.8-28.7 (25.0±2.0) 22.5-26.5 (25.0±1.5)

Lip width 7 7-8 (7.3±0.5) 7-8 (7.3±0.5)

Lip height 4 4-5 (4.2±0.4) 4.0

Length of stoma 13 13-15 (13.5±0.6) 13-14 (13.2±0.5)

Corpus 119 100-133 (120±9) 114-124 (120±4)

Isthmus 16 15.5-22.5 (20±2) 18-22 (19.5±1.5)

Basal bulb length 20 19-24 (20.5±1.5) 18-20 (19±0.7)

Pharynx 153 140-176 (159±10) 150-163 (158±5)

Excretory pore from ant. end 102 94-114 (103±5) 104-110 (105±2)

Nerve ring from ant. end 99 92-110 (101±5) 95-106 (100±3.5)

Dierid from ant. end 118 106-127 (116±6) 114-124 (117±3.5)

Cardia 4 4-5 (4.3±0.5) 4-5 (4.1±0.4)

Basal bulb width 16 14-18 (15±1.0) 14-16 (14.8±0.8)

Anterior sac (Spermatheca) 36.5 12-38 (37±8) --

Genital branch 64 48.5-77.0 (61.5±8.5) --

Post-uterine branch 29.5 17.5-38.5 (28.5±6.0) --

VBD 25.5 22.0-28.5 (25.5±2.0) --

Vulva- anus distance 128 127-159 (144±11) --

Rectum/cloaca 19 19-21 (20.0±0.5) 17-20 (18.5±1.5)

Tail 55.5 53.5-67.5 (59.5±4.0) 39.5-44.5 (42.5±1.5)

ABD 15 13-17 (15±1) 18-20 (19±0.5)

Phasmids from anus 16 14-22 (17.0±2.5) 20-24 (22±1.5)

Testis -- -- 208-268 (229±21)

Spicules -- -- 22-24 (23±0.7)

Gubernaculum -- -- 12-14 (13.2±0.7)

    38 

 

A

Fig. 4. Pseudacrobeles mucronatus sp. n. A-C. Anterior region showing variable lip region and stoma, D. Spermatheca, E. Post-uterine sac, F. Female posterior region, G. Lateral lines, H. Male posterior region, I&J. Male tail tip showing variable mucro length (Scale bars = 20µm).

40

B C

F

G

HJI

E

D

Subfamily Acrobelinae Thorne, 1937

Diagnosis: Lip region having cephalic probolae with complicated structures,

labial probolae large and exhibit triradiate symmetry, deep clefts present between

the lips. Cheilostom a broad chamber, gymnostom short, dorsal metastegostom

with a small tooth. Pharyngeal corpus cylindrical, basal bulb with well developed

grinder. Nerve ring usually surrounding the base of corpus or anterior half of

isthmus. Female gonad single, reflexed, ovary extending beyond vulva, straight

or with flexure posterior to vulva; spermatheca present at anterior flexure of

gonad. Males without bursa. Genital papillae present.

Type genus: Acrobeles Linstow, 1877

Other genera: Acrobeloides (Cobb, 1924) Thorne, 1937

Acrobelophis Andrassy, 1984

Acroukrainicus Holovachov, Boström & Susulovsky, 2001

Cervidellus Thorne, 1937

Chiloplacoides Heyns, 1994

Chiloplacus Thorne, 1937

Nothacrobeles Allen & Noffsinger, 1971

Paracrobeles Heyns, 1968

Pentjatinema Heyns & Swart, 1998

Placodira Thorne, 1937

Scottnema Timm, 1971

Stegelleta Thorne, 1938

Stegelletina Andrassy, 1984

Triligulla Siddiqi, 1993

Zeldia Thorne, 1937

    41 

 

Genus Acrobeles Linstow, 1877

Diagnosis: Body small to large (L=0.3-1.1 mm). Cuticle single or double, with

large annules, with or without longitudinal striae, punctations and/or pores.

Lateral field with two or three incisures, if cuticle double then often with

undulating internal pseudolines. Amphids relatively distinct, circular. Labial

probolae long, deeply bifurcated. Each prong with at least seven tines, its tip

usually with two elongate , separated apical tines.cephalic probolae high,

triangular, separate and fringed by numerous tines. Stoma cephaloboid with

distinct cheilorhabdia that are large and spherical in cross section. Pharyngea

corpus cylindrical to fusiform. Excretory pore position varying from very anterior

to opposite basal bulb. Female reproductive system cephaloboid, spermatheca

and post-uterine sac small to large. Vulva flush with body, occasionally sunken.

Males with three pairs of precloacal papillae, five pairs of postcloacal papillae

and one median papillae on the precloacal lip. Tails in both sexes conical, usually

with acute tip.

Acrobeles mariannae Andrassy, 1968

(Fig. 5)

Measurements: In Table 3.

Females: Body, straight to slightly curved ventrad, gradually tapering at both

extremities. Cuticle double, both layers similar, coarsely annulated. Annules

about 1.5-2.0 µm wide at mid body. Lateral fields with four incisures, slightly

elevated from body contour, outer incisures smooth, inner ones are crenate.

Labial probolae 7-11 µm high, bifurcated to about 50-60% of their length, each

    42 

 

arm bearing membranous tines varying in length and shape, rounded to rod-like,

and apical ones longer than the posterior ones. Inner sides with 6-8 tines and

outer sides with 7-9 tines, terminal tines ‘T’ shape. Cephalic probolae forming a

circle around the labials, each probola triangular, flap like, with 7 or 8 tines at

primary and secondary axil margins. Primary and secondary axils with similar

morphology (‘U’ shaped), with two guard processes each. Third tine of the

secondary axil is long and forwardly directed. Amphidial apertures rounded, at

the base of lateral cephalic probolae. Stoma cephaloboid, rhabdia distinctly

demarcated, cheilostom wide, with rounded rhabdia, gymnostom narrower than

cheilostom and as wide as stegostom, dorsal metarhabdion with tooth. Pharyngeal

corpus cylindrical 4-8 times longer than isthmus. Isthmus short, distinctly

separated from corpus by transverse marking. Basal bulb pyriform, with well

developed grinders. Nerve ring surrounding the corpus near corpus-isthmus

junction, at about 66-71% of pharynx length. Excretory pore far forward 26-38

µm from anterior end. Hemizonid in the posterior half of isthmus. Dierids at the

level of basal bulb. Cardia short, conoid surrounded by the intestinal tissue.

Intestine with small and granular cells, and wide lumen.

Reproductive system mono-prodelphic, ovary reversed, with or without

double flexure posterior to vulva. Oocytes arranged in one or two rows in the

germinal zone and in a single row in proliferative zone of ovary. Oviduct short.

Spermatheca reduced, less than the corresponding body diam. in length. Uterus

tubular, more than two corresponding diam. long, differentiated into a proximal

glandular and a distal muscular with thin walls. Post-uterine sac small, less than

the vulval body diam. in length. Vagina tubular, perpendicular to body axis, one

    43 

 

third of body diam. long. Vulva a transverse slit. Rectum 1.0-1.3 anal body diam.

long, anus an arcuate transverse slit. Tail conoid, gradually narrowing to an acute

terminus. Phasmids distinct, 33-39% or about one anal body diam. posterior to

anus.

Male: Not found.

Habitat and locality: Soil collected from the barren fields and road side ditches

near All India Radio station, Anoopshahr road, Aligarh.

Voucher specimen

Twelve females on slides Acrobeles mariannae/1-5 deposited in the

nematode collection of Department of Zoology, Aligarh Muslim University,

Aligarh.

Remarks

A. mariannae is a terrestrial species. It is widely distributed and is known

from The Netherlands, Hungary, Pakistan, Sudan, Kenya, Namibia, South Africa,

Brazil, Paraguay and Krakatau Islands, Hungary. This species is easily

differentiated from the other species of the genus by its small body and a very

anteriorly located excretory pore. The morphology and morphometric values of

our population of A. mariannae corresponds well with those of described

populations. A. mariannae is reported for the first time from India.

    44 

 

Table 3: Measurements (in µm) of Acrobeles mariannae Andrassy, 1968 Mean and S.D. given in parenthesis

Characters Females (n=10)

L 440-497 (472 ± 20)

a 15.7-18.3 (16.9 ± 1)

b 3.6-4.1 (3.9 ± 0.15)

c 9.5-11.9 (10.6 ± 0.6)

c′ 2.3-3.0 (2.6 ± 0.2)

V 60-62 (61 ± 0.5)

Maximum body width 25-30 (28 ± 1.5)

Lip width 13-14 (13.1 ± 0.4)

Stoma length 11-14 (11.5 ± 1)

Corpus 79-86 (84 ± 2)

Isthmus 11-22 (16 ± 4)

Basal bulb length 21-23 (21.5 ± 0.5)

Basal bulb width 15-18 (16 ± 1)

Pharynx 114-128 (122 ± 5)

Excretory pore from anterior end 26-38 (33 ± 3.5)

Nerve ring 74-89 (82 ± 4)

Cardia 5-6 (5.5 ± 0.5)

Anterior sac (Spermatheca) 6-13 (9 ± 2)

Genital branch 46.5-79.0 (63 ±10)

Post-uterine sac 9-16 (13.5 ± 2)

Vulval body diameter (VBD) 24-30 (28 ±1.5)

Vulval anus distance 131-153 (141 ± 8.5)

Rectum 18-20 (19 ± 1)

Tail 41-48 (45 ± 2)

Anal body diameter (ABD) 15-19 (17 ± 1.5)

Phasmids from anus 15-17 (16 ± 0.5)

    45 

 

Genus Acrobeloides (Cobb, 1924) Thorne, 1937

Diagnosis: Body length varying from 0.3-1.2 mm. cuticle annulated, lateral fields

with two to five incisures extending generally to tip of tail. Lips three, labial

probolae hemispheroid or conoid, point always uni-tipped. Cephalic probolae

present, but low, not strongly differentiated. Proximal half of oesophagous,

fusiform. Stoma cephaloboid, narrow. Vulva near two-thirds of body length,

ovary with double postvulval flexures. Males mostly unknown. Tail short and

plump, broadly rounded or conoid.

Acrobeloides glandulatus sp. n.

(Fig. 6, 7)

Measurements: In Table 4.

Females: Body cylindrical, tapering gradually towards both ends, slightly

ventrally curved after fixation. Cuticle with strong transverse annules, annuli 3-

4µm wide at midbody. Lateral fields 22-30% of the mid-body diam., with five

incisures; outer incisures crenate and irregularly aerolated. Lips six, amalgamated

in pairs, flattened. Primary axils distinct, with smooth margins. Secondary axils

scarcely demarcated. Three low and rounded labial probolae. Amphidial

apertures slit-like. Stoma cephaloboid. Cheilostom wide, with small and ovoid

rhabdia, gymnostom and stegostom slightly narrower than cheilostom,

metastegostom with a small tooth on dorsal rhabdia. Pharyngeal corpus

cylindrical, 4.7-7.5 times isthmus length. Corpus-isthmus junction distinguished

by transverse markings. Isthmus smaller than basal bulb. Basal bulb ovoid or

pyriform, with strongly developed grinder. Nerve ring surrounding the isthmus in

    47 

 

anterior half, or at 73-78% of neck length. Excretory pore at the level of basal

bulb, 77-92% of neck length. Dierids at level or slightly posterior of basal bulb

region. Cardia conoid, surrounded by intestinal tissue. Intestine with distinct wide

lumen, intestinal cells small, granular in appearance with distinct nuclei.

Reproductive system mono-prodelphic. Ovary reversed, straight or with

double flexure in its postvulvular part. Oocytes arranged in two or more rows in

the germinal zone. Oviduct short, tubular. Spermatheca 0.6-2.0 times the

corresponding body diam. long, with few sperms. Uterus long, differentiated in

an elongated proximal glandular part and a short distal muscular part with wide

and distinct lumen. Post-uterine sac 1-2 vulval body diam. long. Vagina with

thick walls, one-third of body diam. A pair of spheroid glands associated with the

vagina, each gland is arranged on either side of vagina, both glands seems to

open into the vaginal lumen through a common duct. Vulva transverse, lips

slightly protruded. Rectum less than one anal body diam. long. Tail conoid, 1.7-

2.1 anal body diam. long, with rounded terminus. Phasmid at 46 – 55 % of tail

length.

Males: General appearance similar to that of female, but with slightly smaller

body, ventrally curved in the posterior region adopting ‘J’ shape. Reproductive

system monorchic. Testis reflexed ventrally anteriorly on the right side of

intestine. Tail conoid, ventrally curved, with rounded terminus. Genital papillae

eight pairs; three pairs pre-cloacal (subventral), five pairs post-cloacal. Of the

five post-cloacal pairs two pairs (one subventral and one lateral) anterior to

phasmid, three pairs (one dorsal, one lateral and one subventral) near the tail

terminus. Spicules strong, small manubrium, calamus broad, slightly ventrally

    48 

 

curved lamina with pointed tip. Gubernaculum straight, more than half of spicule

length, narrow and pointed distally.

Type habitat and locality: Soil collected from a ploughed field at Nohati village,

Madrak, Aligarh.

Type specimens

Holotype female on slide Acrobeloides glandulatus sp. n./1, nine females

and eight males (paratypes) on slides Acrobeloides glandulatus sp. n./2-10

deposited in the nematode collection of Department of Zoology, Aligarh Muslim

University, Aligarh.

Diagnosis and relationship

Acrobeloides glandulatus sp. n. is characterized by a body length of 625-

825 µm in females and 558-717 µm in males. Lateral fields with five incisures.

Low and rounded labial probolae. Pharyngeal corpus 4.7-7.5 times isthmus

length. Well developed spermatheca (0.6-2.0 times corresponding body diam.

long) and long post-uterine sac (1-2 vulval body diam. long). Presence of one pair

of gland on either side of vagina. Spicules 41-48 µm long. Straight

gubernaculum, with narrow and pointed distal end.

The new species resembles Acrobeloides bodenheimeri (Steiner, 1936)

Thorne, 1937 in general morphological characters, morphometric values and

body size but differs from it in having longer post-uterine sac (57-72 µm vs 29-55

µm), variable shape of ovary (with or without double flexure vs with double

flexure), larger corpus-isthmus ratio (5-8 vs 3.8-4.2), longer spicules (41-48 µm

    49 

 

vs 35-39 µm) and in the shape of gubernaculum (straight and pointed distal tip vs

ventrally curved and blunt distal tip).

    50 

 

Table 4: Measurements (in µm) of Acrobeloides glandulatus sp. n. Mean and S.D. given in parenthesis

Characters Holotype

female Paratype females

(n= 9) Paratype males

(n= 8)

L 825 625-825 (746±58.5) 558-717 (644±53)

a 17 15.8-19.3 (17.6±1.2) 14.5-18.2 (16.2±1.2)

b 5.4 4.5-5.5 (5.1±0.3) 4.3-5.1 (4.9±0.2)

c 19 15.4-19.0 (17.3±1.2) 14.5-17.0 (15.5±0.9)

c´ 1.9 1.7-2.1 (1.9±0.13) 1.5-1.8 (1.6±0.1)

V 69 68-71 (69.5±1.0) --

Maximum body width 47 32.5-50.5 (43.0±6.0) 30.5-47.5 (40.0±4.5)

Lip width 12 11-13 (11.5±0.7) 10-12 (11.0±0.5)

Lip height 5 5-6 (5.4±0.5) 5-6 (5.1±0.3)

Length of stoma 14 13-14 (13.7±0.5) 13-14 (13.2±0.4))

Corpus 109 102-110 (105.5±3.0) 81-106 (93.5±7.0)

Isthmus 17 14-22 (17±2.5) 15-20 (17±20)

Basal bulb length 26 22.0-26.5 (24.5±1.5) 19.0-23.5 (21.5±2.0)

Pharynx 153 138-152 (146±5) 120-146 (132±9)

Excretory pore from ant. end 126 115-130 (124±5.5) 101-130 (115±11)

Nerve ring from ant. end 112 103-113 (109±3.5) 85-102 (96±6)

Dierid from ant. end 136 126-141 (133.5±5.5) 108-138 (124±10)

Anterior sac (Spermatheca) 54 23-72 (44±13) --

Genital branch 215 137-274 (206±41) --

Post-uterine branch 59 57-72 (64±6) --

VBD 42 32.5-50.5 (41±5.5) --

Vulva- anus distance 214 160-214 (184±16) --

Rectum/cloaca 25 20-26 (24.5±1.5) 33-41 (36±2)

Tail 43 40.5-45.5 (43.5±1.5) 36.5-44.5 (41±2.0)

ABD 23 19-25 (22.5±1.5) 20.5-29.5 (25.5±2.5)

Phasmids from anus 20 20-25 (21.5±2.0) 20-27 (24±2)

Testis -- -- 294-381 (343±32)

Spicules -- -- 40.5-47.5 (43.5±2.5)

Gubernaculum -- -- 21.5-27.5 (25.5±2.0)

    51 

 

A B C

I

D

E

F

HG J

Fig. 7. Acrobeloides glandulatus sp. n. A&B. Anterior region showing stoma and lip region, C. Glands associated with vagina, D. Vulval region, E&F. Cuticular markings, G&H. female posterior region, I&J. Male posterior region showing spicules and gubernaculum (Scale bars = 20µm).

53

Genus Cervidellus Thorne, 1937

Diagnosis: Very small nematodes ranging from 0.3 to 0.5mm. Cuticle finely

annulated, lateral fields with two, three or five incisures. Lip margins with U-

shaped refractive elements, cephalic probolae six, triangular or leaf-like. Labial

probolae thin, Y-shaped, occasionally with secondary tines. Pharyngeal corpus

cylindrical. Female genital apparatus cephaloboid. Tails of both sexes conoid

with pointed tip.

Cervidellus neoalutus sp. n.

(Fig. 8, 9)

Measurements: In Table 5.

Females: Body slender, slightly ventrally curved after fixation, gradually tapering

towards both extremities. Cuticle double, transversely annulated, each annule

with two rows of punctations. Annuli 1.8-2.2 µm wide at pharyngeal region and

about 1.7-2.0 µm wide at midbody and tail region. Lateral fields with four

crenated incisures, without areolation, covering about 1/5th of body diam. at

midbody. Lateral lines start at 40-50% of pharynx length from anterior end as

two faint lines and differentiate into four lines at level of basal bulb. The two

inner incisures are more widely separated as compared to the outer ones,

appearing as two pairs of four lines. All incisures reach the tail terminus.

Cephalic region with six probolae, each consisting of five leaf-like elements: in

the centre, the longest and slightly clavate element; more outwards and on both

sides two pairs of shorter and acute elements. Labial probolae about 5µm long

with bifurcation at two levels, primary bifurcation at 2/3rd of probolae length,

    54 

 

secondary bifurcation apical. Amphidial apertures small, rounded. Stoma

cephaloboid. Cheilostom wide, with granular rhabdia. Gymnostom and stegostom

with less distinct rhabdia, narrower than cheilostom. Dorsal metastegostom with

a minute tooth like projection. Pharyngeal corpus cylindrical 2.5-3.0 times

isthmus length. Basal bulb pyriform or ovoid with well developed grinder. Nerve

ring at 63-71 % of neck length, surrounding isthmus in its anterior half. Excretory

pore at the level or slightly anterior to nerve ring. Dierids in the isthmus region, at

71-78% of neck length. Cardia rounded to conoid, surrounded by intestinal tissue.

Intestinal walls with differentiated rectangular cells, intestine with wide lumen.

Reproductive system mono-prodelphic. Ovary reversed, extending

posterior to vulva, postvulval flexure absent. Oocytes with large nuclei, arranged

in a single or double row in the germinal zone and in a single row in the

maturation zone. Oviduct short, spermatheca well developed, about 1.5 vulval

body diam. long. Uterus simple, tubular with narrow lumen and without any

differentiation. Post-uterine sac 1.0-2.5 times vulval body diam. long. Vagina

narrow, tubular, one-fourth of body diam. Vulval opening a small transverse slit.

Tail conical, with acute terminus. Phasmids distinctly visible, about 0.6-1.0 anal

body diam. posterior to anus.

Males: Anterior region similar to that of females. Reproductive system

monorchic. Testis reflexed ventrad anteriorly, on right side of intestine. Spicules

cephaloboid, manubrium round, calamus slightly narrower than manubrium,

lamina ventrally curved, with acute terminus. Gubernaculum straight, with well

developed crura. Genital papillae seven pairs, three pairs precloacal (subventral)

and four pairs postcloacal. Out of the four postcloacal papillae, two pairs (one

    55 

 

subventral & one lateral) anterior to phasmid and two pairs (one subdorsal & one

lateral) posterior to phasmid. A mid-ventral papilla on the anterior cloacal lip is

also present.

Type habitat and locality: Soil from a barren field near Central School, Bad

village, Mathura.

Type specimens

Holotype female on slide Cervidellus neoalutus sp. n./1, nine females and

three males (paratypes) on slides Cervidellus neoalutus sp. n./2-8 deposited in

the nematode collection of Department of Zoology, Aligarh Muslim University,

Aligarh.

Diagnosis and relationship

Cervidellus neoalutus sp. n. is characterized by a double cuticle, lateral

fields with four crenate incisures with inner ones more widely separated than

outer ones. Symmetrical lips, with refractive elements, labial probolae with

bifurcation at two levels and small post-uterine sac about 1.2-2 times vulval body

diam. in length.

The new species closely resembles C. alutus (Siddiqi, 1993) Shahina and

De Ley, 1997 in having double cuticle, symmetrical lips with refractive elements

but differs from it in the length of stoma (14-15 µm vs 10 µm), smaller post-

uterine sac (1.2 – 2 vs 2.3 - 2.6 times vulval body diam. long) and in the presence

of males (males absent in C. alutus).

    56 

 

Table 5: Measurements (in µm) of Cervidellus neoalutus sp. n. Mean and S.D. given in parenthesis

Characters Holotype female

Paratype females (n= 9)

Paratype males (n= 3)

L 554 485-566 (529.5±23) 500-538 (522±16.5)

a 20.7 18.3-22.3 (20±1.3) 17.5-19 (18.5±0.7)

b 3.9 3.5-3.9 (3.7±0.2) 3.5-4.0 (3.8±0.2)

c 10.4 9.8-11.3 (10.3±0.4) 13.5-14.5 (14±0.5)

c’ 3.2 2.7-3.3 (3.1±0.2) 1.8-2.0 (1.9±0.1)

V 59 57-59 (58.5±0.5) --

Maximum body width 26.5 22-31 (26.5±2.3) 28-29 (28.5±0.5)

Lip width 13 12-13 (12.5±0.5) 12-13 (12.5±0.5)

Lip height 7 6-7 (6.5±0.5) 7

Length of stoma 14 14-15 (14.5±0.5) 14

Corpus 86 85-90 (87±1.5) 85-87 (86.5±1.0)

Isthmus 32.5 27.5-33.5 (31.5±2.0) 24.5-31.5 (28.5±3.0)

Basal bulb length 22.5 21-24 (23±1.0) 22-24 (22.5±1.0)

Pharynx 141.5 135-145 (142±3.5) 136-141(138±4)

Excretory pore from ant. end 96 84-96 (92±3.5) 96-97 (96.5±0.5)

Nerve ring from ant. end 101 87-101 (94±3.5) 92-96 (94.5±1.5)

Dierid from ant. end 111 98-112 (107±5) 110

Basal bulb width 15 14-16 (15.5±0.5) 15-16 (15.2±0.5)

Anterior sac (Spermatheca) 37.5 29-43.5 (37±4.5) --

Genital branch 51 44.5-63.5 (50.5±5.5) --

Post-uterine branch 51 35.5-59.5 (47±7) --

VBD 27 22-31 (26±2.5) --

Vulva- anus distance 173 157-179 (167±7) --

Rectum 18 15-20 (18±1.5) --

Tail 53 48.5-55.5 (52±2.5) 37-39 (37.5±1.0)

ABD 17 15-19 (17±1) 20-21 (20.2±0.5)

Phasmids from anus 17 11-17 (15±2) 15-17 (16±1.0)

Testis -- -- 229-274 (246 ± 20)

Spicules -- -- 22-23 (22.5±0.5)

Gubernaculum -- -- 12-13 (12.5±0.5)

    57 

 

Fig. 9. Cervidellus neoalutus sp. n. A. Anterior region showing amphidial aperture, B&C. Anterior region showing probolae and stoma, D. Spermatheca, E. Post-uterine sac, F. Female posterior region, G. Male posterior region, H. Spicules and gubernaculum, I. Lateral lines (Scale bars = 20µm).

59

A B C

GED

F I H

Cervidellus minutus sp. n.

(Fig. 10, 11)

Measurements: In Table 6.

Females: Body small, slightly ventrally curved after fixation. Cuticle simple, with

transverse annulations. Lateral fields 12-14% of mid-body diam. wide, with three

incisures. Outer incisures crenate extending up to tail tip, central incisure ends at

phasmids. Cephalic probolae six, with refractive margins, each consisting of five

leaf- like elements. Primary and secondary axils similar in shape. Labial probolae

reduced, rarely visible in light microscope. Amphidial apertures small, ovoid.

Cheilostom with granular rhabdia, gymno- and stego-rhabdions poorly

developed. Pharyngeal corpus slightly fusiform, sometimes with wide lumen, 3.1-

3.7 times isthmus length. Corpus-isthmus junction distinguished by faint

transverse markings. Basal bulb spheroid, with well developed grinder. Nerve

ring at 56-61% of neck length, encircling isthmus in its anterior half. Excretory

pore at the level or just posterior to corpus-isthmus junction. Excretory duct

distinctly sclerotized. Dierids in the isthmus region or at the level of basal bulb.

Intestine with wide lumen. Cardia conoid about 2-3µm long, surrounded by

intestinal tissue.

Reproductive system mono-prodelphic, on right side of intestine. Ovary

reversed, without flexure posterior to vulva. Oocytes arranged in a single or

double row in germinal zone and in a single row in proliferative zone. Oviduct

short, not clearly demarcated. Spermatheca weakly developed, smaller than the

corresponding body diam. Uterus uniform in thickness, without any

differentiation between glandular and muscular part, lumen not visible. Post-

    60 

 

uterine sac less than one vulval body diam. long. Vagina straight, about 1/3rd of

body diam. with slightly thickened walls. Vulva transverse, slit like. Rectum

slightly more than one anal body diam. long. Rectal glands barely visible. Tail

conical, about 2-3 anal body diam. long, terminus acute, with subterminal dorsal

projection. Phasmids with distinct opening, about half anal body diam. posterior

to anus.

Male: Not found.

Type habitat and locality: Collected from the rhizosphere of Guava (Psidium

guajava) and Cashew-nut (Anacardium occidentale), in mixed plantation, from

Satpada, near Chilka lake, Orrisa, India.

Type specimens

Holotype female on slide Cervidellus minutus sp. n./1 and five females

(paratypes) on slides Cervidellus minutus sp. n./2-4 deposited in the nematode

collection of Department of Zoology, Aligarh Muslim University, Aligarh.

Diagnosis and relationship

Cervidellus minutus sp. n. is characterized by its small body (226-266

µm), lateral fields with three incisures. Lips with refractive margins. Reduced

labial probolae. Distinctly sclerotized excretory duct. Small spermatheca (5-6

µm) and post-uterine sac (less than one anal body diam.). Conoid tail, with acute

terminus and hook-like subterminal dorsal projection.

The new species differs from all other species of the genus in having a

subterminal dorsal projection in female tail. It, however, closely resembles C.

neftasiensis Boström, 1986 and C. vexilliger (de Man, 1880) Thorne, 1937 in

general morphometrics, shape of labial region, number of lateral lines. It can be

    61 

 

differentiated from C. neftasiensis in having comparatively smaller body length

(226-266 µm vs 268-330 µm), smaller spermatheca (5-6µm vs 13-28µm), and

relatively smaller genital branch (26-36µm vs 37-71µm). C. minutus sp. n. also

differs from C. vexilliger in having smaller spermatheca (5-6 µm vs 11-37 µm)

and relatively smaller post-uterine branch (7-8 µm vs 8-47 µm).

    62 

 

Table 6: Measurements (in µm) of Cervidellus minutus sp. n. Mean and S.D. given in parenthesis

Characters Holotype

female Paratype females

(n= 5)

L 253 226-266 (251±13)

a 17 16.3-18.8 (17.1±0.8)

b 3 2.9-3.1 (3±0.1)

c 12.2 10.5-12.2 (11.5±0.6)

c’ 2.3 2.3-2.8 (2.5±0.1)

V 67 63.5-66.5 (64.5±1.0)

Maximum body width 15 14-16 (14.5±0.5)

Lip width 8 8-9 (8.5±0.5)

Lip height 5 5-6 (5.2±0.5)

Length of stoma 7 6-8 (7±0.5)

Corpus 56 50.5-56.5 (55±2)

Isthmus 16 14-18 (16±1.5)

Basal bulb length 13 12-13 (12.5±0.5)

Pharynx 85 77-86 (83.5±3)

Excretory pore from ant. end 53 51.5-59.5 (54.5±2.5)

Nerve ring from ant. end 48 47.5-51.5 (49.5±1.5)

Dierids from ant. end 67 67.5-69.5 (67.5±1)

Basal bulb width 9.9 9.9

Anterior sac (Spermatheca) 5 5-6 (5.5±0.5)

Genital branch 32 26-36 (31±4.5)

Post-uterine branch 8 7-9 (7.5±0.5)

VBD 14 13-15 (13.5±0.5)

Vulva- anus distance 63.5 61-73 (67±4)

Rectum 12 10-12 (11.5±1.0)

Tail 21 20-24 (22±1.5)

ABD 9 8-10 (8.5±0.5)

Phasmids from anus 5 4-5 (4.2±0.4)

    63 

 

A B C

ED

F

GFig. 11. Cervidellus minutus sp. n. A. Pharyngeal region, B Anterior region showing cephalic

probolae with refractive margins, C Anterior region showing stoma, D. Lateral lines, E Female reproductive system, F. Posterior region, G. Tail tip showing dorsal projection (Scale bars = 20µm).

65

Genus Chiloplacus Thorne, 1937

Diagnosis: Body 0.3-1.0 mm long. Cuticle annulated, lateral fields with 3-6 lines.

Lips three. Labial probolae biacute or bifurcate (apically incised), symmetrical or

assymetrical, with broad “shafts”. Cephalic probolae small, generally with two

incisures. Pharyngeal corpus cylindrical. Post-vulval uterine sac of variable

lengths. Female tail straight, short, cylindroid, terminus broadly rounded. Male

tail ventrally bent, phasmids posterior to lateral caudal papilla.

Chiloplacus aligarhensis sp. n.

(Fig. 12, 13)

Measurements: In Table 7.

Females: Body slender, straight or slightly ventrally curved after fixation. Cuticle

annulated, annules 2.3-3.3 µm wide at mid-body, with irregular punctations

throughout the body length. Lateral fields about 1/4th body diam. at midbody,

with five incisures. Lateral lines arise at about two stoma lengths from anterior

end and from middle of procorpus differentiate into five lines that extends upto

the tail terminus except the central incisure that ends at phasmids. Lip region with

six lips. Cephalic probolae small, with deep primary axils and shallow secondary

axils. Labial probolae high (6-7µm), with shallow bifurcation forming finely

developed prongs. Stoma cephaloboid, rhabdions clearly differentiated;

cheilostom wide with minute oval or triangular rhabdia, gymnostom slightly

narrower than cheilostom and as wide as stegostom, metastegostom with small

tooth like projection. Pharyngeal corpus cylindrical, 8-11 times isthmus length.

Corpus-isthmus junction demarcated by faint transverse markings. Isthmus short,

    66 

 

17-22 µm long, basal bulb ovoid, with well developed grinder. Nerve ring

surrounding corpus in its posterior half, at 60-66% of pharynx length. Excretory

pore at 60-72% of pharynx length. Dierids 5-8 annules posterior to excretory

pore. Cardia short, conoid, surrounded by intestinal tissue. Intestine with wide

lumen and thin walls in its anterior region, cell differentiation not visible in

anterior and posterior regions of intestine. Cells in the mid-intestine region well

differentiated, rectangular in shape, granular in appearance with distinct nuclei.

Reproductive system mono-prodelphic, ovary reversed, without flexure

posterior to vulva, sometimes with swollen germinal portion with oocytes

arranged in one or two rows. Oocytes in a single row in the proliferative zone.

Oviduct short. Spermatheca well developed, longer than the corresponding body

diam.. Uterus tubular, more than two corresponding body diam. long,

differentiated into a proximal glandular part and a distal swollen muscular part

with thin walls. Post-uterine sac well developed, 2.5-4.0 vulval body diam. long.

Vagina muscular, anteriorly inclined, about half of vulval body diam. long. Vulva

transverse, slit-like, vulval lips may be slightly protruded. Rectum 1.0-1.3 anal

body diam. long. Tail subcylindrical with rounded terminus. Phasmids distinct,

1.0-1.5 anal body diam. posterior to anus.

Males: General morphology similar to that of females. Body J-shaped after

fixation. Reproductive system monorchic. Testis reflexed ventrally anteriorly,

with flexure on right side of intestine. Apical germinative zone with three to four

rows of spermatogonia, maturation zone with spermatocytes and differentiated

sperms at its distal end. Vas deferens highly granular in appearance without any

valve or sphincter at the junction of maturation zone. Ejaculatory duct with

    67 

 

similar appearance as of vas deferens but with distinct lumen containing sperms.

Tail conoid, ventrally curved. Genital papillae eight pairs; three pairs pre-cloacal,

ventro-lateral in position and five pairs post-cloacal. Of the post-cloacal pairs,

one ventro-lateral and one lateral pair anterior to phasmids, one pair dorso-lateral

near tail terminus and two terminal ventro-lateral pairs. A single median pre-

cloacal papilla present on the anterior cloacal lip. Spicules slightly ventrally

arcuate, manubrium round and bent ventrally, calamus with thin walls, lamina

thick, ventrally curved, bearing a longitudinal incisure from the calamus,

Gubernaculum well developed, trough-shaped, about half of spicule length, with

serrated margins at its proximal end.

Type habitat and locality: Soil around the rhizosphere of grasses from a barren

field near village Lodha on Aligarh-Khair road.

Type specimens

Holotype female on slide Chiloplacus aligarhensis sp. n./1, ten females

and eleven males (paratypes) on slides Chiloplacus aligarhensis sp. n./2-11

deposited in the nematode collection of Department of Zoology, Aligarh Muslim

University, Aligarh.

Diagnosis and relationship

Chiloplacus aligarhensis sp. n. is characterized by the long body (0.75-

0.83 mm in females and 0.72-0.82 mm in males), lateral fields with five

incisures, labial probolae with well developed prongs, pharyngeal corpus 7-10

times isthmus length, ovary without flexures posterior to vulva, well developed,

offset spermatheca, long post-uterine sac (85-109 µm), female tail subcylindrical,

    68 

 

2-3 anal body diam. long, male tail conoid 45-52 µm long, spicules 30-35µm

long and gubernaculum about half of spicules length.

The new species resembles C. tenuis Rashid & Heyns, 1990, C. subtenuis

Rashid & Heyns, 1990 and C. magnus Rashid & Heyns, 1990 in general

morphometrics, shape and body size. However, from C. tenuis it can be

differentiated in the shape of labial probolae (prongs small and straight vs prongs

long and curved towards each other), longer pharyngeal corpus in females (155-

177µm vs 105-150µm), longer female tail (42-49µm vs 25-40µm. From C.

subtenuis it differs by slightly smaller pharynx in females (197-216µm vs 219-

240µm), males of C. subtenuis differs in having longer tail (45-52µm vs 38-

43µm), wider body diam. at cloaca (22-27µm vs 18-20µm), slightly larger c′

value (1.9-2.3 vs 1.6-1.8) and in the arrangement of genital papillae (three pre-

cloacal & five post-cloacal pairs vs four pre-cloacal & four post-cloacal pairs).

From C. magnus the new species differs by its smaller body size (753-829µm vs

883-1522µm), slightly posterior position of nerve ring and excretory pore (60-

66% & 60-72% vs 35-59% & 38-56% of the pharyngeal length respectively),

smaller pharynx (197-216 µm vs 222-289 µm in females and 191-209 µm vs 211-

245 µm in males), relatively smaller spermatheca (35-47 µm vs 48-99 µm),

smaller genital branch (73-113µm vs 143-218µm), smaller vulva-anus/tail ratio

(4.2-5.0 vs 5.2-8.0) and in having smaller testis (294-412µm vs 421-741µm).

    69 

 

Table 7: Measurements (in µm) of Chiloplacus aligarhensis sp. n. Mean and S.D. given in parenthesis

Characters Holotype

female Paratype females

(n= 10) Paratype males

(n= 11)

L 754 753-829 (786±28) 716-817 (772±33)

a 23 23.1-28.9 (26.5±2) 23-31 (26.5±2.2)

b 3.5 3.5-4.1 (3.8±0.2) 3.6-4.3 (3.9±0.2)

c 15.7 15.7-18.5 (16.8±0.9) 14.4-16.5 (15.5±0.7)

c´ 2.7 2-2.9 (2.5±0.3) 1.9-2.3 (2.1±0.1)

V 67 65.5-68 (67±0.5) --

Maximum body width 32 26.5-38.5 (30.5±3.5) 25.5-35 (29.5±3)

Lip width 10.5 10-11 (10.5±0.5) 10-11 (10.5±0.5)

Lip height 7 7-8 (7.5±0.5) 7-8 (7.5±0.5)

Length of stoma 11 11-12 (11.5±0.5) 10-12 (11±0.5)

Corpus 169 155-177 (163±7) 148-165 (156±7)

Isthmus 19 16.5-22 (18.5±1.5) 11.5-23.5 (17.5±3)

Basal bulb length 24.5 22.5-26.5 (24±1) 22.5-25.5 (24±1)

Pharynx 212.5 197-216 (205±6.5) 191-209 (198±7)

Excretory pore from ant. end 127 124-145 (136±6.5) 127-143 (135±5)

Nerve ring from ant. end 119 118-134 (127±5) 118-172 (140±20)

Dierid from ant. end 142 140-165 (152±7.5) 141-155 (148±5)

Basal bulb width 16.5 14.5-17.5 (16±1) 14-16.5 (15±1)

Anterior sac (Spermatheca) 39 34.5-47 (39.5±4.5) --

Genital branch 98 73-113 (88.5±12) --

Post-uterine branch 106 85-109 (95±8) --

VBD 30 25-38 (30.5±3.5) --

Vulva- anus distance 204 201-234 (215±12) --

Rectum/cloaca 21.5 21.5-23.5 (23±1) 29.5-33.5 (31.5±1.5)

Tail 48 42-49 (46.5±2.5) 45-52 (50±2)

ABD 17.5 16.5-23.5 (19.5±2) 22-27 (24±2)

Phasmids from anus 23.5 18.5-26 (23±2) --

Testis -- -- 294-412 (354±41)

Spicules -- -- 30-35 (33.5±2)

Gubernaculum -- -- 17-21 (19.5±1)

    70 

 

Fig. 13. Chiloplacus aligarhensis sp. n. A. Anterior region showing labial probolae, B. Anterior region showing stoma, C. Post-uterine sac, D. Uterus and spermatheca, E. Female posterior region, F. Male posterior region, G. Spicules and gubernaculum, H. Lateral lines (Scale bars = 20µm).

72

A B C

D

GF

E H

Genus Nothacrobeles Allen & Noffsinger, 1971

Diagnosis: Body length varying from 0.4 to 0.9 mm. Cuticle with broad annules,

with or without longitudinal striae or punctations. Lateral fields with two to four

incisures. Cephalic probolae in pairs, low, with or without serrate sculpture.

Labial probolae short to moderately long, slightly bifurcate and bordered with

small tines; outer rim or shaft with basal ridge. Amphids minute. Pharyngeal

corpus cylindrical. Female gonad cephaloboid. Tails in both sexes conical with

acute tip. Phasmids anterior to the lateral caudal papilla in males.

Nothacrobeles punctatus sp. n.

(Fig. 14, 15)

Measurements: In Table 8.

Females: Body robust, slightly ventrally curved after fixation. Cuticle simple,

transversely annulated, annuli 3-4 µm wide at midbody, with two rows of

punctuations. Lateral fields about 1/6th of the body diam. at midbody. Incisures

start about two stoma lengths from anterior end as two crenate lines and

differentiate into four lines at the level of isthmus. Outer incisures crenate, inner

ones smooth, areolation absent. Lateral fields extend up to the tail terminus.

Labial probolae 8-10 µm long, bifurcate for half their length, with a prominent

dentate basal ridge protruding outwards towards the cephalic probolae. Prongs

divergent and bifurcate, outer longer than the inner. Each prong with six

triangular tines on inner margin and eight on outer margin. Primary and

secondary axils deep with ‘U’ and ‘V’ shape respectively. Amphidial openings

minute, oval or round in shape. Stoma cephaloboid. Cheilostom wide, with

    73 

 

almost triangular rhabdia. Gymnostom narrower than cheilostom and as wide as

stegostom. Dorsal metarhabdion with a minute tooth. Pharyngeal corpus slightly

fusiform 3.5-4.0 times isthmus length. Corpus-isthmus junction with transverse

markings. Basal bulb spheroid, with well developed grinder. Nerve ring at 66-

78% of neck length, surrounding isthmus in anterior half. Excretory pore at the

level or just posterior to nerve ring. Hemizonid about two annules posterior to

excretory pore. Dierids in the isthmus region or at the level of basal bulb. Cardia

conoid, 5-7µm long, surrounded by intestinal tissue. Intestine with distinct wide

lumen throughout its length, intestinal cells well differentiated, rectangular in

shape.

Reproductive system mono-prodelphic, ovary reversed, without any

flexure. Oocytes arranged in a single row throughout. Oviduct short, tubular,

made of eight differentiated cells. Spermatheca well developed, usually longer

than the corresponding body diam., with few sperms. Uterus well developed,

about two to three times body diam. long. Uterus differentiated into a proximal

glandular part with narrow lumen and a swollen distal muscular part with wide

lumen. Distal and proximal parts of uterus separated by slight constriction. Post-

uterine sac less than one vulval body diam. in length. Vagina thick walled, about

1/3rd of vulval body diam. Vulva transverse, slit-like. Rectum slightly less than

one anal body diam. long, with three rectal glands. Tail conical, 2-3 anal-body

diam. long, with acute terminus. Phasmids located at less than one anal body

diam. posterior to anus.

Males: General morphology similar to females. Posture slightly straighter than

females but more ventrally curved posteriorly. Reproductive system monorchic,

    74 

 

testis reflexed ventrally, flexure on right side of intestine. Germinal zone with

two to three rows of spermatogonia, leading to the maturation zone with

spermatocytes and differentiated sperms at its distal end. Vas deferens with

numerous small round sperms. Ejaculatory duct wider than vas deferens with

narrow lumen. Tail conical, ventrally curved, terminating in an acute mucro.

Phasmids 1.3-1.5 anal body diam. posterior to anus. Genital papillae eight pairs;

two pairs subventral precloacal, one pair subventral adcloacal and five pairs

postcloacal. Of five postcloacal pairs, two pairs (one lateral and one subventral)

are located just posterior to phasmid and three pairs (one subdorsal, one

subventral and one lateral) near the tail tip. Spicules ventrally arcuate;

manubrium rounded; calamus cylindrical; lamina swollen near calamus.

Gubernaculum well developed, slightly bent anteriorly.

Type habitat and locality: Soil sample collected from a potato field, Shahrekord,

Iran

Type specimens

Holotype female on slide Nothacrobeles punctatus sp. n./1, three females

and six males (paratypes) on slides Nothacrobeles punctatus sp. n./1-4 deposited

in the nematode collection of Department of Zoology, Aligarh Muslim

University, Aligarh.

Diagnosis and relationships

Nothacrobeles punctatus sp. n. is characterized by having two rows of

punctations in each annule; bifurcate labial probolae, with divergent prongs;

spermatheca 28-50 µm long; post-uterine sac less than one vulval body diam.

    75 

 

long; female tail conical with acute terminus; phasmids at 21-32% of tail length;

spicules 45-49 µm long and gubernaculum 30-34 µm long.

The new species resembles Nothacrobeles subtilis Allen and Noffsinger,

1971 and N. maximus Allen and Noffsinger, 1971 in general morphometrics.

However, the new species differs from N. subtilis in cuticular punctations (with

punctations vs without punctations), more anterior position of phasmid (21-32%

vs near middle of tail) and in the presence of males. From N. maximus it can

easily be differentiated by the structure of cuticle (without longitudinal striations

vs with longitudinal striations), cuticular punctations (with punctations vs without

punctations), lateral fields (incisures crenate anterior to dierids then smooth

throughout the body length vs incisures crenate posterior to dierids) and in the

presence of males (males absent in N. maximus).

    76 

 

Table 8: Measurements (in µm) of Nothacrobeles punctatus sp.n. Mean and S.D. given in parenthesis

Characters Holotype

female Paratype females

(n= 3) Paratype males

(n= 6)

L 716 646-721 (683±35.0) 668-749 (710.5±28.0)

a 18.5 16.3-18.7 (17.6±1.0) 18.2-19.5 (18.9±0.4)

b 4.6 3.7-4.6 (4.2±0.3) 4.3-4.9 (4.6±0.2)

c 10 10.0-11.5 (10.9±0.6) 10.7-12.6 (11.5±0.6)

c’ 2.6 2.1-2.7 (2.5±0.3) 1.7-2.0 (1.9±0.1)

V 63 62-63 (62.5±0.5) --

Maximum body width 39 39-40 (38.9±0.5) 35-40 (37.5±1.5)

Lip width 17 15-17 (16.5±1.0) 16-17 (16.0±0.5)

Lip height 15 14-15 (14.5±0.5) 13-14 (13.5±0.8)

Length of stoma 13 10-18 (13.5±3.0) 13-15 (13.5±0.8))

Corpus 101 98-115 (105.0±6.5) 88-106 (99.5±6.0)

Isthmus 28 25-31 (28.0±2.0) 25-31 (27.5±2.0)

Basal bulb length 28 28-30 (28.5±1.0) 26-29 (27.5±1.2)

Pharynx 155 149-171 (160.5±9.0) 138-163 (152.5±8.5)

Excretory pore from ant. end 120 94-120 (110±10) 111-127 (118.5±5.0)

Nerve ring from ant. end 109 109-134 (115±11) 106-112 (109.5±2.5)

Dierid from ant. end 132.5 104-133 (123±11) 125-141 (132.5±5.0)

Cardia 7 5-7 (6.0±0.8) 5-7 (6.5±0.8)

Basal bulb width 21 21-22 (21.0±0.5) 20-22 (20.8±0.8)

Anterior sac (Spermatheca) 49.5 27.5-49.5 (42±9) --

Genital branch 100 96-100 (98.0±1.5) --

Post uterine branch 26.5 24-27 (24.5±1.0) --

VBD 34 34-38 (35.5±1.5) --

Vulva- anus distance 194 182-202 (192±7) --

Rectum 23 22-24 (23±1) --

Tail 71 56.5-71.5 (63.5±6.5) 57-66 (62.0±3.0)

ABD 26.5 24.5-26.5 (25.5±1.0) 30-34 (32.0±1.5)

Phasmids from anus 21 12-22 (17.5±4.0) 22-25 (23.0±1.5)

Testis -- -- 325-360 (341±12)

Spicules -- -- 45-49 (46.5±1.5)

Gubernaculum -- -- 30-32 (30.5±0.5)

    77 

 

H I

E

F

G

C

B DA

Fig. 15. Nothacrobeles punctatus sp. n. A. Anterior region showing stoma, B&C. Labial probolae, D. Vulval region showing post-uterine sac, E. Glandular part of uterus and spermatheca, F. Cuticular punctations, G. Female posterior region, H. Spicules and gubernaculum, I. Lateral lines (Scale bars = 20µm).

79

Genus Stegellata Thorne, 1938

Diagnosis: Body 0.3-0.7 mm long. Cuticle with transverse as well as longitudinal

striations, dividing each other to form small quadrate blocks. Lateral fields with

three to five incisures. Cephalic probolae simple, low. Labial probolae tuning

fork-shaped with thin shaft and U-like prongs. Pharyngeal corpus cylindrical.

Female genital organs cephaloboid. Female tail broadly, male tail narrowly

rounded.

Stegellata ophioglossa Andrassy, 1967

(Fig. 16)

Measurements: In Table 9.

Females: Body small, straight to slightly ventrally curved after fixation. Cuticle

with transverse and longitudinal striations, giving it a tessellated appearance.

Lateral fields distinct, occupying about 1/5th of the midbody diam.. Incisures

three, outer ones crenate. Lip region with six separate lips having rounded

margins. Labial probolae with wide base, 4-6µm long, bifurcate to about 1/3rd of

their length. Prongs divergent and equal in size, forming a semicircular arc.

Amphidial apertures round. Stoma cephaloboid, cheilostom wide, with small

ovoid rhabdia. Gymnostom narrower than cheilostom, and as wide as stegostom.

Metastegostom with a minute tooth like projection on dorsal rhabdia. Pharyngeal

corpus cylindrical, with distinct lumen, 3.3-4.5 times isthmus length. Corpus-

isthmus junction distinctly demarcated. Basal bulb ovoid or pear-shaped with

well a developed grinder. Nerve ring surrounding the base of corpus at 60-67% of

neck length. Excretory pore opposite the trailing end of nerve ring or at 62-71%

    80 

 

of neck length. Hemizonid just posterior to the excretory pore. Dierids at about

65-71% of neck length, lying in the anterior half of isthmus. Cardia short, conoid,

surrounded by intestinal tissue. Intestine with wide lumen at its anterior region.

Reproductive system mono-prodelphic. Ovary posteriorly directed

without any flexure. Oocytes arranged in two rows in the germinal zone and in a

single row in the proliferative zone. Oviduct short, tubular. Spermatheca less than

the corresponding body diam long, without sperms. Uterus simple, tube like,

undifferentiated. Post-uterine sac less than one vulval body diam. long. Vagina,

thick walled, with sclerotization. Vulva transverse, slit like. Rectum 1.2-1.6 anal

body diam. long. Tail cylindrical, 2.6-3.5 anal body diam. long, with

approximately 20 ventral annuli. Tail terminus flat. Phasmids one anal body

diam. posterior to anus.

Males: Not found.

Habitat and locality: Soil sample collected from the root zone of Sorghum sp.

from village Nohati, Madrak and from the root zone of Trifolium alexandrinum

from village Pisava, Chandaus, Aligarh.

Voucher specimens

17 females on slides Stegellata ophioglossa (N)/1-9 and 12 females on

slides Stegellata ophioglossa (P)/1-4 deposited in the nematode collection of

Department of Zoology, Aligarh Muslim University, Aligarh.

Remarks

S. ophioglossa is a terrestrial nematode, this species have previously been

recovered from sandy soils and dune sands. It is widely distributed and has been

described from Europe (Hungary, Italy), Asia (Uzbekistan, Mongolia), Africa

    81 

 

(Senegal) and South America (Venezuela). This is the first report of S.

ophioglossa from India, where, it was recovered from sandy as well as from

loamy soil. Despite the change in type of habitat the measurements and

descriptions of our specimens agree well with that of Stegellata ophioglossa

Andrassy, 1967. However slight variations from the original description were

observed in the height of labial probolae (4-6 µm vs 8-11 µm), relatively smaller

pharynx (96-112 µm vs 110-130 µm), smaller post-vulval uterine sac (less than

corresponding body diam. vs as long as or longer than corresponding body diam.)

    82 

 

Table 9: Measurements (in µm) of Stegellata ophioglossa Andrassy, 1967 Mean and S.D. given in parenthesis

Characters Females (n= 10)

Nohati population Females (n=12)

Pisava population

L 327 – 386 (347 ± 16) 341 – 409 (347 ± 16)

a 18.3 – 23 (21 ± 1.5) 19.2 – 22 (20.2 ± 0.8)

b 3.1 – 3.7 (3.4 ± 0.2) 3.2 – 3.7 (3.4 ± 0.2)

c 10.3 – 11.9 (11.1 ± 0.5) 10 – 11.4 (10.6 ± 0.5)

c’ 2.6 – 3.4 (3 ± 0.2) 2.9 – 3.7 (3.1 ± 0.2)

V 62 – 64.5 (63 ± 0.5) 61 – 63.5 (62 ± 0.5)

Maximum body width 15 – 18 (16.5 ± 1) 15.5 – 20 (18 ± 1)

Lip width 6 – 7 (6 ± 0.3) 6 – 7 (6.9 ± 0.3)

Length of stoma 9.0 9.0 – 10 (9.5 ± 0.5)

Corpus 66.5 – 72.5 (70 ± 2) 69.5 – 77 (72 ± 2)

Isthmus 14.5 – 21.5 (18 ± 1.5) 18.5 – 24.5 (22 ± 1.5)

Basal bulb length 14 – 16 (14.5± 0.5) 13 – 17 (14.5± 1)

Pharynx 96 – 112 (102.5 ± 4.5) 104 – 114 (108 ± 3)

Excretory pore from ant. end 67.5 – 73.5 (69 ± 1.5) 69.5 – 75 (73 ± 1.5)

Nerve ring from ant. end 61.5 – 68.5 (65.5 ± 2.5) 68 – 73 (70.5 ± 1.5)

Dierid from ant. end 72.5 – 79 (74.5 ± 2.5) 75 – 82 (78.5 ± 2)

Basal bulb width 9 – 12 (10 ± 0.5) 10 – 13 (11 ± 0.5)

Anterior sac (Spermatheca) 10 – 14 (12 ± 1.5) 7 – 10 (9 ± 1)

Genital branch 36.5 – 65.5 (45.5 ± 7.5) 32.5 – 48.5 (40 ± 4)

Post uterine branch 8 – 12 (10 ± 1.2) 8 – 11 (10 ± 1)

VBD 14 – 17 (15.5 ± 1) 15 – 19 (17 ± 1)

Vulva- anus distance 89 – 113 (98 ± 6.5) 92 – 119 (105 ± 7)

Rectum 13 – 15 (14 ± 0.5) 14 – 16 (15 ± 0.5)

Tail 28.5 –34.5 (31 ± 1.5) 30.5 –37.5 (35 ± 2)

ABD 9 – 12 (10.5 ± 1) 10 – 12 (11 ± 0.5)

Phasmids from anus 9 – 10 (9.5 ± 0.5) 7 – 15 (10.5 ± 2)

    83 

 

Genus Zeldia Thorne, 1937

Diagnosis: Body length between 0.6-1.0 mm. Cuticle annulated, annuli with or

without punctations or tessellation. Lateral fields with three to five incisures,

outer lines sometimes crenate. Lateral fields with or without areolations. Cephalic

probolae triangular, flap-like, low with setose projections. Labial probolae low

and rounded to elongate and shallowly to deeply bifurcate at one level; without

tines. Amphidial apertures elongate-oval. Lining of cheilostom without or with 1-

3 tooth-like processes. Pharyngeal corpus long and cylindrical. Intestine often

with prerectum. Postvulval uterine branch short or absent. Tails in both sexes

conoid, with pointed or finely rounded tip. Males rare or unknown in most

species.

Zeldia tridentata Allen and Noffsinger, 1972

(Fig.19, 20)

Measurements: In Table 10.

Females: Body robust, gradually tapering toward both the ends, straight or

slightly curved ventrally. Cuticle with transverse annules, 1.6 – 2 µm wide at the

pharynx base and midbody and 1.6 - 1.8 µm wide at tail. Each annule with two

rows of punctations. Lateral fields with three lines, outer ones crenate, areolated

in the pharyngeal region. Lip region 10-11 µm wide, 4-5µm high. Labial

probolae low, with round margins and shallow grooves. Primary axils deep, with

dentate guard processes. Amphidial apertures oval. Cheilostom with prominent

cylindrical walls, each cheilorhabdion associated with a structure having three

teeth. Gymnostom longer than cheilostom, metastegostom with a small tooth like

    85 

 

process on dorsal wall. Pharyngeal corpus cylindrical, 7.9-9.2 times isthmus

length. Isthmus shorter than basal bulb. Basal bulb ovoid, 21-26 x 18-21 µm,

with a grinder at its middle or slightly anterior. Cardia conoid, surrounded by

intestinal tissue. Intestine with wide lumen. Nerve ring at 59-66% of neck length,

surrounding the distal part of the corpus. Excretory pore just posterior to nerve

ring or one to two annules anterior to hemizonid. Deirids in the posterior region

of corpus, or at 67-78 % of neck length.

Reproductive system mono-prodelphic, ovary reversed, on right side of

intestine, with or without additional flexures posterior to vulva. Oocytes usually

arranged in a single row throughout the ovary length. Spermatheca scarcely

developed. Oviduct short. Uterus tubular, without any differentiation. Post-

uterine sac short, 0.3-0.5 times vulval body diam. long. Vagina with thick walls,

slightly anteriorly directed. Rectum 21-28 µm long. Tail elongate conoid, 4-5

anal body diam. long, with acute terminus. Phasmids 1-3 µm posterior to anus.

Male: Not found

Habitat and locality

Soil sample collected from an orchard of guava and cashew-nut near

Chilika lake, Puri, Orissa.

Voucher specimens

9 females on slides Zeldia tridentata/1-2 deposited in the nematode

collection of Department of Zoology, Aligarh Muslim University, Aligarh.

Remarks

Z. tridentata is distinguished from other species of the genus by the

presence of three teeth associated with each cheilorhabdion and the longer tail.

    86 

 

This species is widely distributed throughout the world and has been collected

from India, Jamaica, Philippine Islands, Srilanka, Taiwan, Thailand, and

Venezuela. Most of the species of the genus were collected from the soil or sand

around the root zone of different plants. The present population was also

collected from the sandy soil, around the root zone of Guava and Cashew Nut

plantations.

The measurements and descriptions of our specimens agree well with that

of Zeldia tridentata Allen & Noffsinger, 1972. However differences from

original population were found in the lateral fields (outer incisures crenated vs

smooth). Rashid et al., 1984, collected two females of this species from Itapebi,

Lombardia, Brazil, (Host: Theobroma cacao). They Illustrate and redescribed the

species and added more details to the original description. In Brazilian

population, cuticular punctations were not observed, however the punctations

have been reported in the original descriptions and are distinctly visible in our

population also. They also mentioned the ovary with a double flexure posterior to

vulva but in our population the specimens without any flexure were also found

along with the specimens having double flexure. In Brazilian population the

phasmid lies at about 5-6 annules posterior to anus however, in our population

phasmid lies just posterior to anus.

    87 

 

Table 10: Measurements (in µm) of Zeldia tridentata Allen and Noffsinger, 1972 Mean and S.D. given in parenthesis

Characters Females (n= 9)

L 635-779 (724±46)

a 19.0-23.5 (20.8±1.3)

b 3.7-4.0 (3.9±0.1)

c 8.5-9.0 (8.8±0.2)

c’ 4.1-4.9 (4.5±0.3)

V 61-62 (61.5±0.3)

Maximum body width 30.5-40.5 (35±3.0)

Lip width 10-11 (11±0.5)

Lip height 4-5 (4.5±0.5)

Length of stoma 15-17 (15.5±0.5)

Corpus 135.5-155.5 (147±6.5)

Isthmus 14-19 (16.5±1.5)

Basal bulb length 20-25.5 (23.5±1.5)

Pharynx 170-200 (187±9.0)

Excretory pore from ant. end 109-126.5 (121±5.5)

Nerve ring from ant. end 105-121.5 (116.5±5.5)

Dierid from ant. end 124-149 (137.5±9.0)

Cardia 5-6 (5±0.5)

Basal bulb width 18-21 (19±1)

Anterior sac (Spermatheca) 7-14 (10.5±2.5)

Genital branch 70-135 (9±21)

Post uterine branch 12-18 (13.5±2.0)

VBD 31.5-40.5 (35.5±3.5)

Vulva- anus distance 166-209 (194±14)

Rectum 21-28 (24.5±2.0)

Tail 73-87 (82.5±4.0)

ABD 16-21 (17.5±1.5)

Phasmids from anus 1-3 (2±0.7)

    88 

 

Superfamily Panagrolaimoidea Thorne, 1937

Diagnosis: Buccal cavity a single, fairly wide chamber, sometimes tending to

taper at its base. Metastom anisoglottoid and anisomorphic, narrower than

anterior part; telostom small and narrow. Pro-, meso- and telorhabdions usually

conspicuously thickened; cheilorhabdions sometimes thickened; metarhabdions

not thickened but metastom segments often bearing small teeth. Pharyngeal

corpus cylindrical or with swollen valveless median bulb; a narrow isthmus and a

basal bulb with grinders. Female genital organ prodelphic, ovary reflexed once,

usually well down into body; a short post-vulval sac sometimes present. Tip of

male gonad usually reflexed. Male supplements papilloid, arranged in pairs. No

bursa. Phasmids well discernible.

Type family: Panagrolaimidae Thorne, 1937

Other subfamilies: Alirhabditidae Suryawanshi, 1971

Brevibuccidae Paramonov, 1956

Family Panagrolaimidae Thorne, 1937

Diagnosis: Cuticle annulated, lateral fields distinct. Lip region practically without

probolae. Lips three or six, moderately developed.Amphids located on lateral

lips, small. Stoma consisting of the usual six elements, its anterior section

(cheilo- and gymnostom) spacious, stegostom tapering, metastom with a small

tooth-like projection. Pharynx consisting of corpus, isthmus and bulb. Female

genital organ prodelphic, reflexed part extending far behind vulva, rarely with a

simple flexure. Anterior separated portion of uterus serving as a spermatheca.

Postvulval uterine sac present. Males mostly abundant. Preanal genital papillae in

    90 

 

5-7 pairs. Tail conoid or elongate, in male generally shorter than in female.

Phasmids always distinct.

Type subfamily: Panagrolaiminae Thorne, 1937

Other subfamilies: Panagrellinae Andrassy, 1976

Tricephalobinae Andrassy, 1976

Turbatricinae Goodey, 1943

Baujardiinae Andrassy, 2005

Subfamily Tricephalobinae Andrassy, 1976

Diagnosis: Cuticle finely annulated, lateral fields distinct. Lip region without

probolae. Lips three or six, moderately developed. Cheliostom small and less

sclerotized, gymnostom well developed, stegostom tapering, Pharyngeal corpus

with bulb like median swelling. Terminal bulb very strong. Female genital organ

panagrolaimoid. Postvulval uterine sac present. Males mostly abundant. Genital

papillae 6-7 pairs. Tail uniformly conoid in female. Phasmids always distinct.

Type genus: Tricephalobus Steiner, 1936

Other genus: Halicephalobus timm, 1956

Genus Tricephalobus Steiner, 1936

Diagnosis: Body length between 0.5-1.0 mm. cuticle finely annulated, lateral

fields narrow. Head broad, continuous with body, lips three, separate. Cheilostom

short and not sclerotized, gymnostom well developed, stegostom funnel- shaped.

Pharyngeal corpus posteriorly swollen, bulb-like. Terminal bulb very strong.

Female genital organ panagrolaimoid, postvulval branch present. Both sexes

    91 

 

equally common. Spicules with narrowed proximal end, gubernaculum thin.

Genital papillae six or seven pairs. Tail conoid in female, and strongly narrowed

at posterior half in male, terminus sharp.

Tricephalobus quadripapilli sp.n.

(Fig.18, 19)

Measurements: In Table 11.

Females: Body slender, slightly ventrally curved after fixation. Cuticle simple,

with fine transverse annulations. Lateral fields narrow with two incisures,

occupying about 1/9th of the body diam. at midbody. Incisures arise at level of

median bulb as two smooth lines and extend up to the level of phasmids. Labial

probolae absent. Lips three, low and rounded, continuous with body contour.

Amphids indistinct. Stoma tubular, cheilostom with indistinct rhabdia.

Gymnostom slender, tube like, surrounded by a granular band like structure.

Stegostom as long as gymnostom, with slightly tapering dorsal wall. Pharyngeal

corpus posteriorly swollen into an oval median bulb, 2.7 – 3.7 times isthmus

length. Isthmus tubular. Basal bulb pyriform, with well developed grinder. Nerve

ring at 67-73% of neck length, surrounding isthmus at its middle. Excretory pore

at level of basal bulb. Dierids situated at the level of basal bulb or slightly

posterior to pharynx. Cardia short, conoid, surrounded by intestinal tissue.

Intestine with distinct wide lumen.

Reproductive system mono-prodelphic. Ovary reversed, without any

flexure, extending upto anus level. Oocytes arranged in multiple rows in germinal

zone and in a single row in maturation zone. Oviduct short, tubular, separated

    92 

 

from spermatheca by constriction. Spermatheca in continuation of uterus,

separated from it by slight constriction. Uterus well developed, differentiated into

a proximal glandular part and a distal muscular part with distinct lumen. Distal

part is twice as long as muscular part, both parts were separated by a constriction.

Post-uterine sac continuous with uterus, small, less than half vulval body diam. in

length. Vagina slightly anteriorly directed, about 1/3 - 1/2 of vulval body diam. in

depth. Vulva transverse, slit-like. Vulval lips slightly protruded. Rectum about

one anal body diam. long. Tail conical, 2.6-3.7 anal-body diam. long, with

narrowly rounded terminus. Phasmids 1.3-1.8 anal body diam. posterior to anus.

Males: Body slightly smaller than females. General morphology similar to that of

females. Reproductive system monarchic. Testis reflexed ventrally, flexure on

right side of intestine. Germinal zone with two to three rows of spermatogonia,

leading to the maturation zone with spermatocytes. Tail conical, ventrally curved,

strongly narrowed in its posterior half, terminating in a rounded tip. Phasmids

indistinct. Genital papillae four pairs; one subventral pair precloacal, situated at

level of spicule head, three pairs postcloacal. Of three postcloacal pairs, one

subventral pair is located at less than one anal body diam. posterior to cloacal

opening. Two pairs (one subventral and one subdorsal) located just anterior to the

beginning of narrower part of the tail. Spicules broad, with rounded manubrium,

broad calamus, ventrally arcuate lamina, with two longitudinal incisures from the

calamus. Spicule tip rounded. Gubernaculum small, less then half of spicules

length.

Type habitat and locality: Farm yard manure collected from a fallow field,

Poonch Jammu & Kashmir, India.

    93 

 

Type specimens

Holotype female on slide Tricephalobus quadripapilli sp. n./1; nine

females and ten males (paratypes) on slides Tricephalobus quadripapilli sp. n./2-

6, deposited in the nematode collection of Department of Zoology, Aligarh

Muslim University, Aligarh.

Diagnosis and relationship

Tricephalobus quadripapilli sp. n. is characterized by very fine transverse

annulations, a granular band around the gymnostom region, lateral fields with

two incisures, a well developed median bulb, ovary extending upto rectum

region, a constriction between glandular and muscular parts of uterus, sett off

spermatheca, broad spicules about 18-24 µm long, genital papillae four pairs and

tail with narrowed posterior half region.

The new species closely resembles T. steineri (Andrassy, 1952), Rühm,

1956 in general morphology and morphometrics. However, it can be

differentiated from T. steineri in having smaller post-uterine sac (less than half vs

one corresponding body diam. long), smaller tail (2.6-3.7 vs 4 ABD long in

females and 2.2-2.5 vs 3.5 ABD long in males), number of precloacal genital

papillae (one vs three).

    94 

 

Table 11: Measurements (in um) of Tricephalobus quadripapillii sp. n. Mean and S.D. given in parenthesis

Characters Holotype

female Paratype females

(n=9) Paratype males

(n=10)

L 491 434-517 (476±29) 391-473 (439±29)

a 17.7 17.5-19 (18.3±0.5) 18-20.5 (19.5±0.8)

b 5.3 4.6-5.8 (5.1±0.3) 4.2-5.1 (4.7±0.3)

c 10.8 9.7-12.8 (10.9±1.0) 10.5-12.5 (11.3±0.6)

c’ 3.1 2.6-3.7 (3.1±0.3) 2.2-2.5 (2.4±0.09)

V 61 58.5-62.5 (61±1.0) --

Maximum body width 27.5 23-29 (26±2.0) 20-25 (22.5±1.5)

Lip width 7 7-8 (7.3±0.5) 6-7 (6.7±0.4)

Length of Stoma 11 9-11 (10±0.5) 9-10 (9.2±0.5)

Corpus 56.5 54.5-59.5 (56.5±2) 49.5-60.5 (54.5±3.5)

Isthmus 19 16-22 (19±1.5) 17-29 (22.5±4)

Median bulb width 12 11-13 (12±0.5) 10-11 (10.5±0.5)

Basal bulb length 18 17-20 (18.5 ±1.0) 17-21 (18±1)

Basal bulb width 15 13-15 (14±0.5) 11-14 (12.5±1)

Pharynx 93 89-99 (94±2.5) 83-107 (94±7)

Excretory pore from anterior end 90 80-91 (85±4) 73.5-89 (81±5.5)

Nerve ring 67.5 63.5-69.5 (66.5±2) 57.5-74 (66±5)

Genital branch 113 90-127 (109±11.5) --

VBD 28 22.5-28.5 (26.5±1.5) --

Vulva- anus distance 144.5 122-164 (142±13) --

Rectum/cloaca 16 13-17 (15±1) 14-18 (16±1.5)

Tail 45.5 38.5-49.5 (44±3) 35.5-43.5(39±2.5)

ABD 15 12-15 (14±1) 15-18 (16.5±1)

Phasmids from anus 22 20-25 (22±1.5) --

Testis -- -- 196-261 (230±26)

Spicules -- -- 18-25 (21±2)

Gubernaculum -- -- 7-10 (8.5±1)

 

    95 

 

Fig. 19. Tricephalobus quadripapilli sp. n. A. Pharyngeal region, B. Anterior region showing stoma, C. Anterior region showing granular band around gymnstom, D. Lateral lines, E. Vulval region showing post-uterine sac, F. Female reproductive tract showing uterus, G. Female posterior region, H. Spicules and gubernaculum, I. Male posterior region (Scale bars = 20µm).

97

H G

F

I

A B

C

D

E

Family Brevibuccidae Paramonov, 1956

Diagnosis: Lips six, stoma relatively small, nearly twice as long as wide.

Pharyngeal corpus cylindrical or posteriorly swollen into a strong terminal bulb.

Female genital organ panagrolaimoid. Reflexed part of ovary not reaching to

vulva. Post-vulval uterine sac absent.

Type and only subfamily: Brevibuccinnae Paramonov, 1956.

Subfamily Brevibuccinae Paramonov, 1956

Diagnosis: Lips six, stoma relatively small, nearly twice as long as wide or

smaller or equal to lip region width. Pharyngeal corpus cylindrical or posteriorly

swollen. Reflexed part of ovary not reaching to vulva. Post-vulval uterine sac

absent. Both arms of spicules are equal or unequal, species often with unusually

long spicules.

Type genus: Brevibucca Goodey, 1935

Other genera: Cuticonema Sanwal, 1959

Plectonchus Fuchs, 1930

Genus Brevibucca Goodey, 1935

Diagnosis: Stoma short, expanding slightly at base, cheilostom and gymnostom

thick walled, forming half stoma depth; stegostom with an inwardly projecting

short tooth. No pharyngeal collar. Pharyngeal corpus cylindrical, isthmus short,

terminal bulb with grinder. Vulva posterior, gonad mono-prodelphic. Ovary

    98 

 

reversed not reaching vulval opening. A uninucleate gland cell on each side of

the uterus close to vagina. Testis outstretched. Spicules paired but of unequal

size. Gubernaculum present. Bursa absent. Genital papillae eight pairs.

Brevibucca postamphidia sp. n.

(Fig. 20, 21)

Measurements: In Table 12.

Females: Body slender, slightly arcuate upon fixation, tapering towards both

ends. Cuticle with fine transverse and longitudinal striations. Punctations fine,

sub-cuticular, transversely arranged. Lips separate, with minute hair like papillae.

Amphidial openings large, oval, post-labial at about 1/3rd of stoma length from

anterior end. Amphidial canal and fovea prominent. Cheilostom well developed,

slightly longer than wide, with thick cuticularised walls. Gymnostom short and

cuticularised. Stegostom anisomorphic. Dorsal wall provided with a tooth, each

subventrals with a smaller tooth. Pharyngeal corpus cylindrical, muscular, about

2.5 times isthmus length. Corpus isthmus junction distinct. Isthmus tubular. Basal

bulb ovoid, with well developed grinder and single haustrulum. Excretory pore

at level of corpus region, at about 38-43% of the pharyngeal length. Paired

excretory cells present just above basal bulb. Nerve ring encircling isthmus just

below corpus-isthmus junction, approximately at 62-66% of pharyngeal length.

Pharyngo-intestinal junction with well developed cardia consisting of three flaps.

Intestinal cells large, granular. Intestinal lumen variable in width.

    99 

 

Female reproductive system mono-prodelphic, ovary reflexed. Oviduct

narrow, joining ovary at a point slightly posterior to anterior tip. Spermatheca set

off by a slight dilation. Uterus undifferentiated, filled with embryonated eggs

and /or sperms. Up to ten eggs may be present at a time in the uterus. Vagina

strongly muscular, vaginal lumen unusually curved. Vulva a small transverse slit,

situated about 2.5 anal body diam. anterior to the anus. A uninucleate gland cell

on each side of the uterus close to vagina, connected by a duct to the uterus.

Post-uterine sac absent. Rectum 1.5-1.9 anal body diam. long, usually with wide

lumen. Tail extremely long filiform, 11-24 anal body diam., with fine tip.

Phasmidial openings distinct, 2-3 anal body diam. posterior to anus. Phasmidial

glands extending to just below the rectum.

Males: Body smaller than females, strongly curved ventrally in the posterior

region. Anterior end similar to that of females. Testis single, straight,

outstretched. Spicules dissimilar and of unequal size, larger one 27-30µm long

and smaller one 20-22μm long. Gubernaculum about half of larger spicule in

length, slightly curved proximally and with a sleeve distally. Genital papillae

eight pairs; three pre-cloacal (two subventrals and one lateral adcloacal), five

post-cloacal pairs. Of five postcloacal pairs, one subventral pair is located just

posterior to cloacal opening while three subventrals and one subdorsal pair are

closely grouped. This group is present just beyond phasmid, at the end of conoid

part of tail. Male tail with conoid part and a long filiform part.

Type habitat and locality: Decaying banana rhizome collected from Haldwani,

Uttarakhand.

    100 

 

Type specimens

Holotype female on slide Brevibucca postamphidia sp. n./1; twenty one

females and twelve males (paratypes) on slides Brevibucca postamphidia sp.

n./2-14, deposited in the nematode collection of Department of Zoology, Aligarh

Muslim University, Aligarh.

Diagnosis and relationship

Brevibucca postamphidia sp. n. is characterized by post-labial amphids

and large amphidial openings. Pharyngeal corpus about 2.5 times isthmus length.

Strongly muscular vagina with unusually curved vaginal lumen. Vulval slit about

2.5 anal body diam. to anus. A uninucleate gland cell on either side of uterus.

Long filiform female tail, about 11-24 anal body diam. in length (c=2.6-3.9).

Males with unequal and dissimilar spicules and eight genital papillae.

The new species closely resembles Brevibucca punctata Timm, 1960 in

general morphology and morphometric values in females but differs from it in

having smaller ‘c’ value in males (5.9-7.7 vs 8-10), structure of testis (outstreched

vs reflexed), size of gubernaculum (12-13 µm vs 18-22 µm) and in the position of

genital papillae (subdorsal pair anterior or almost at level of subventral group vs

subdorsal pair located posterior to subventral group).

    101 

 

Table 12: Measurements (in um) of Brevibucca postamphidia sp. n. Mean and S.D. given in parenthesis Characters Holotype

female Paratype females

(n=21) Paratype males

(n=12)

L 1446 1065-1679 (1380±199) 714-828 (766±35)

a 36.5 28.5-43.0 (35±4.5) 25-30 (27±1.5)

b 6.0 4.5-6.1(5.5±0.6) 3.9-4.2 (4±0.1)

c 3.2 2.6-3.9 (3.1±0.5) 5.9-7.7 (6.9±0.6)

L` 988 795-1073 (953±271) --

a’ 24.9 22.1-34.6 (24.8±27.6) --

b’ 4.2 3.2-4.4 (3.8±1.1) --

c′ 20.1 14.5-25.5 (20±2.8) 4.6-6.2 (5.5±0.5)

V 64 58-70 (63±3.5) --

Maximum body width 39.5 34.5-49.5 (39.5±4.5) 26-32.5 (28.5±2.0)

Lip width 12.8 11-13 (12.5±0.5) 10-11 (10.0±0.3)

Lip height 5 5-6 (5.1±0.4) 4-5 (4.2±0.4)

Stoma length 18 17-19 (18±0.5) 14-15 (14.5±0.5)

Stoma width 7 5-8 (5.5±1.5) 5-6 (5.2±0.4)

Corpus 148 146-173 (157±9.5) 107-122 (115±4.5)

Isthmus 60.5 57.5-74.5 (63±4.5) 47.5-55.5 (50±2)

Basal bulb length 28.5 26.5-32.5 (29.5 ±1.5) 23-26 (24.5±1.0)

Basal bulb width 22.5 21-28 (23±2) 17-18 (17.5±0.5)

pharynx 237.5 231-276 (249±14.5) 177-203 (189.5±6.5)

Excretory pore from anterior end 97 89-112 (99±7) 75-88 (81.5±4.0)

Nerve ring 148.5 148-179 (161±11) 113-129 (121±5)

Anal body diameter(ABD) 22.5 19-26 (22.5±2.0) 18-22 (20.5±1.0)

Genital branch 401 287-612 (412±95) --

Vulval body diameter (VBD) 32 26.5-37.5 (31.5±3.0) --

Vulval anus distance 63 44.5-63.5 (55±5.5) --

Testis -- -- 312-409 (342±26.5)

Rectum 43.5 33-44 (38.5±3.6) --

Tail 458 274-626 (452±94) 101-124 (112±8.0)

Phasmids from anus 59 47.5-64.5 (56-5.0) 25-30 (27±2.5)

Spicule (Small) -- -- 20-22 (20.5±0.8)

Spicule (Large) -- -- 26.5-29.5 (28.5±1)

Gubernaculum -- -- 12-13 (13±0.5)

    102 

 

Fig. 21. Brevibucca postamphidia sp. n. A-C. Anterior region showing parts of stoma, D. Anterior region showing amphid, E. Excretory cell, F. Part of gonad showing junction between oviduct and ovary, G. Female posterior region showing phasmid, H. Rectum, I. Female posterior region showing bivulvate condition, J. Anal opening, K, Anterior part of testes, L&M. Male posterior region showing spicules and gubernaculum

104

A B C D

LKFE

G H I J

M

Genus Plectonchus Fuchs, 1930

Diagnosis: Body slightly curved ventrally when heat-killed. Cuticle with delicate

annulations and fine transverse striae. Lateral fields with two ridges. Lip region

with six low lips slightly separated. Amphids circular. Stoma with a wide and

short cheilostom and gymnostom. Corpus cylindrical, without a distinction

between pro- and metacarpus. Isthmus long and narrow. Basal bulb rounded or

pyriform with distinct grinders. Nerve ring encircling the isthmus. Female

reproductive system monodelphic-prodelphic.

Plectonchus coptaxii sp. n.

(Fig. 22, 23)

Measurements: In Table 13.

Females: Body slender, straight to slightly ventrally curved after fixation,

tapering abruptly and curved strongly beyond vulva. Cuticle 2-3 µm thick,

hyaline, with very fine transverse striations. Lateral fields indistinct. Lips round

with short hair-like papillae. Amphidial apertures oval, post-labial in position.

Stoma very shallow, rhabdions fused and poorly developed, without any

armature. Pharynx panagrolaimoid. Pharyngeal corpus cylindrical, longer than

the combined length of isthmus and basal bulb. Corpus-isthmus junction very

gradual sometimes indistinct. Isthmus tubular, 0.45-0.6 times corpus length.

Basal bulb pyriform, with distinct grinder. Nerve ring encircling isthmus in its

anterior half, at 58-66% of the neck length. Excretory pore in the corpus region,

at 43-47 % of neck length. Dierids and hemizonid indistinct. Cardia conoid,

surrounded by intestinal tissue. Intestine with wide lumen.

    105 

 

Reproductive system monodelphic-prodelphic. Ovary on right side of

intestine, reversed, without flexure, never extending beyond vulva. Oocytes

arranged in two rows in the germinal zone and in single row in the maturation

zone. Oviduct short. Spermatheca small, less than the corresponding body diam.

in length, slightly offset and without sperms. Uterus tubular differentiated into a

proximal and a distal part with thin walls and distinct lumen. The lumen of distal

part usually filled with a single row of granular structures. Vagina short,

anteriorly directed. Vulval lips depressed to form a sunken vulva. Post-uterine

branch absent. A ventral body pore is present slightly posterior to vulva. Rectum

straight, 1.1-1.3 anal body diam. long. Tail elongate conoid, 3.1-4.2 anal body

diam. long, terminus pointed. Phasmids about one anal body diam. posterior to

anus, at 27-35% of tail length.

Males: Anterior end similar to that of females, habitus ventrally curved, more in

the posterior region. Cuticle thick and hyaline like that of females. Testis reflexed

ventrally, on right side of intestine. Spicules dissimilar, unequal and separate.

Right spicule slightly longer than left, straight, slender, with a bifid tip. Left

spicule more robust, arcuate, with fusiform lamina and without a bifid tip.

Gubernaculum heavily sclerotized, more than half of spicule length, strongly

curved at its distal end. Genital papillae eight pairs. Two subventral pairs

precloacal and six pairs postcloacal. Of six postcloacal pairs, two pairs (one

subventral and one lateral) are anterior to phasmid. Two subdorsal pairs and two

subventral pairs are located posterior to phasmid. Tail conoid with acute

terminus.

    106 

 

Type habitat and locality: Organic manure collected from an agricultural field,

Mendhar, Jammu and Kashmir, India.

Type specimens

Holotype female on slide Plectonchus coptaxii sp. n./1; nine females and

eight males (paratypes) on slides Plectonchus coptaxii sp. n./2-5 deposited in the

nematode collection of Department of Zoology, Aligarh Muslim University,

Aligarh.

Diagnosis and relationship

Plectonchus coptaxii sp. n. is characterized by a slender body; thick

cuticle with hyaline portion and fine transverse striations. Lips with hair like

papillae. Amphids oval, post labial in position. Stoma shallow without any

armature, rabdions fused. Ovary reversed, without flexure. Distal part of uterus

with a single row of granular structures. Ventral body pore posterior to vulva.

Female tail elongate conoid, with narrowly rounded terminus. Male tail conoid,

with acute terminus. Spicules symmetric or asymmetric. Gubernaculum strongly

sclerotized, more than half spicule length. Genital papillae eight pairs.

The new species closely resembles P. molgos Massey, 1974 but can be

differentiated by the structure of cuticle (with transverse striae vs without

transverse striae), larger ‘a’ value in females (24.5-31.9 vs 20.4-24.4), smaller ‘b’

value (4.0-4.4 vs 5.1-5.6 in females and 3.9-4.1 vs 4.2-4.9 in males), more

posteriorly located vulva (V= 78-81% vs V=75%), shape of vulval lips

(depressed vs protuberant), tail shape (without constriction vs constricted) and

number and arrangement of genital papillae (eight pairs vs six pairs).

    107 

 

P. coptaxii sp. n. differs from P. wyganti Massey, 1964, in having smaller

body (485-585 µm vs 700 µm in females and 472-517 µm vs 600 µm in males),

smaller ‘b’ value (4.0-4.4 vs 4.5 in females and 3.9-4.2 vs 4.6 in males), greater

‘c’ value in males (12-13 vs 10.8), number and arrangement of genital papillae

(eight pairs vs seven pairs).

    108 

 

Table 13: Measurements (in µm) of Plectonchus coptaxii sp. n. Mean and S.D. given in parenthesis

Characters Holotype

female Paratype females

(n=9) Paratype males

(n=8)

L 530 485-585(536±27.5) 472-517 (495±16)

a 28.2 24.5-31.9 (27.7±2.4) 24.4-32.6 (27.4±2.4)

b 4.1 4.0-4.35 (4.2±0.11) 3.9-4.2 (4±0.1)

c 11.9 9.8-13.0 (11.7±0.9) 12-13 (12.4±0.4)

c’ 3.5 3.1-4.2 (3.5±0.5) 2.1-2.7 (2.3±0.2)

V 79 78-81 (79.5±1.0) --

Maximum body width 19 18-21 (19.5±1.0) 16-21 (18±1.5)

Lip width 6.93 6.93 6.93

Length of Stoma 4 4-5 (4.5±0.5) 3-5 (3.5±0.5)

Corpus 70 64.5-77.5 (72±3.5) 61-71 (68±3)

Isthmus 40.5 31.5-43.5 (38±4) 34.5-46.5 (38.5±3.5)

Basal bulb length 17 16-19 (17.5 ±1.0) 16-17 (16.5±0.5)

Basal bulb width 11 11-12 (11.5±0.5) 9.8

Pharynx 127.5 113-137.5 (128±7) 121-126 (123±1.5)

Excretory pore from anterior end 55.5 54.5-64.5 (58.5±3) 49.5-57.5 (52±2.5)

Nerve ring from anterior end 74 72-88 (81±5) 70-77 (75.5±2.5)

Anterior sac (Spermatheca) 13 12-14 (13±1) --

Genital branch 201 185-248 (212±22) --

VBD 17 15-20 (17±1.5) --

Vulva – anus distance 66 56.5-74 (63.5±5.5) --

Rectum/cloaca 15 15-16 (15.2±0.5) 15-19 (17±1.5)

Tail 45 39.5-54.5 (46±4) 26-42.5 (38±5)

ABD 13 12-14 (13±0.5) 16.5-21 (17±1)

Phasmids from anus 15 14-16 (14.5±1.0) --

Testis -- -- 245-312 (280±24)

Spicules -- -- 19-21 (20±0.5)

Gubernaculum -- -- 12-16 (14±1.5)

 

    109 

 

Fig. 23. Plectonchus coptaxii sp. n. A. Pharyngeal region, B&C. Anterior region showing stoma, D. Anterior region showing amphidial aperture (dorsoventral), E. Female genital tract showing part of uterus, F. Female posterior region showing vulva and anus, G. Male posterior region showing spicules, H. Male posterior region showing gubernaculum (Scale bars = 20µm).

111

A B C D

G

H F

E

Summary

The present work represents a taxonomic study of the nematodes of suborder

Cephalobina. Samples of soil and organic manure were collected from various parts

of the country in addition some samples from old collections were also studied. The

nematodes were isolated by Cobb’s sieving and decantation and modified

Baermann’s funnel techniques. The extracted nematode samples were examined

under stereoscopic microscope. Nematodes were simultaneously killed and fixed in

hot FA (4:1). Later, the nematodes were transferred into glycerine-alcohol (5:95) and

kept in a desiccator for dehydration. Dehydrated nematodes were mounted in

anhydrous glycerine on glass slides using wax as sealing material. All Measurements

were made on specimens mounted in dehydrated glycerine with an ocular

micrometer. De Man’s (1884) formula was used to denote the dimensions of

nematodes. All morphological observations and drawings were made on Nikon 80i

DIC microscope and photographs were taken by ProgRes C3 camera mounted on

Olympus BX 50 DIC microscope.

In all, thirteen species belonging to eleven genera, falling under two

superfamilies, three families and four subfamilies has been described. Of these ten

species which are new to science have been described and illustrated in addition

three known species have also been described. Two known species are being

reported for the first time from India. The terminology used in the text to describe

the parts of stoma is of De Ley et al. (1995).

 

112

 

113

The systematic position of genera and species, described in the present study are

given below

I. Order

Rhabditida

II. Suborder

Cephalobina

III. Superfamilies

1. Cephaloboidea 2. Panagrolaimoidea

IV. Families

1. Cephalobidae

2. Panagrolaimidae

3. Brevibuccidae

V. Subfamilies

1. Cephalobinae

2. Acrobelinae

3. Tricephalobinae

4. Brevibuccinae

VI. Genera

1. Pseudacrobeles

2. Acrobeles

3. Acrobeloides

4. Cervidellus

5. Chiloplacus

6. Nothacrobeles

7. Stegellata

8. Zeldia

9. Tricephalobus

10. Brevibucca

11. Plectonchus

VII. Species

1. Pseudacrobeles ventricauda sp. n.

2. Pseudacrobeles mucronata sp. n.

3. Acrobeles mariannae

4. Acrobeloides glandulatus sp. n.

5. Cervidellus neoalutus sp. n.

6. Cervidellus minutus sp. n.

7. Chiloplacus aligarhensis sp. n.

8. Nothacrobeles punctatus sp. n.

9. Stegellata ophioglossa

10. Zeldia tridentata

11. Tricephalobus quadripapilli sp. n.

12. Brevibucca postamphidia sp. n.

13. Plectonchus coptaxii sp. n.

  114

Part – B Ecology

Introduction

Soil is home to many vertebrate and invertebrate species. Invertebrate

species largely outnumber the vertebrate species. The functional characteristics of

these invertebrates generally depend upon the soil characteristics and thus any

changes in soil condition effect the population dynamics of these invertebrates

and are easily reflected in various forms.

Soil microfauna, such as protozoa and nematodes, are important

constituents of soil foodwebs (Bonkowski, 2004). Their activities regulate the

size and function of fungal and bacterial populations in the soil (Ingham et al.,

1985; Poll et al., 2007), plant community composition (De Deyn et al., 2003) and

rates of carbon (Bradford et al., 2007) and nitrogen (Standing et al., 2006)

turnover. Nematodes are of particular interest because they are the most

numerous soil mesofauna and occupy all consumer trophic levels within the soil

foodweb. Therefore, their community structure can provide important insights

regarding many aspects of ecosystem function (Ritz & Trudgill, 1999; De Ruiter

et al., 2005).

The assemblage of plant and soil nematode species occurring in a natural

or a managed ecosystem constitutes the nematode community. These

communities are sensitive to changes in food supply (Yeates, 1987) and

environment (Bongers et al., 1991; Ettema & Bongers, 1993; Freckman &

Ettema, 1993; Samoiloff, 1987; Wasilewska, 1989). Thus, communities also have

a significant role in regulating decomposition and nutrient cycling (Anderson et

al., 1983; Ingham et al., 1985) and occupy a central position in the soil food web

(Moore & de Ruiter, 1991). When attributes of soil nematode communities are

quantified through measures such as diversity index (Shannon & Weaver, 1949)

115  

or maturity index (Bongers, 1990; Yeates, 1994), an indication of relative soil

biological or ecological health is obtained, which can be used as one measure to

address issues of change in ecological condition of soils in agricultural systems.

Since, nematodes are so abundant and omnipresent in ecosystems, they

serve as elegant indicators of environmental disturbance (Bongers 1990; Ferris et

al., 2001; Yeates, 2003; Höss et al., 2004; Schratzberger et al., 2006; Heininger

et al., 2007). Nematodes possess the most important attributes of any prospective

bioindicator (Cairns et al., 1993): abundance in virtually all environments,

diversity of life strategies and feeding habits (Freckman, 1988; Yeates et al.,

1993), short life cycles, and relatively well-defined sampling procedures. Several

attempt have been made by researchers to develop relationships between

nematode community structure and succession of natural ecosystems or

environmental disturbance (Ettema & Bongers, 1993; Freckman & Ettema, 1993;

Freckman & Virginia, 1997; De Goede & Dekker, 1993; Wasilewska, 1994;

Yeates & Bird, 1994).

Soil microbes play an important role in plant nutrient cycling in organic

farming (Allison, 1973). Additions of organic matter to soil are expected to

increase numbers of bacteriovores and fungivorous nematodes and decrease

numbers of plant-parasitic nematodes (Bohlen & Edwards, 1994; Freckman,

1988; Griffiths et al., 1994). Applications of manure add both organic matter and

microbes, a source of food for the nematodes (Andrén & Lagerlöf, 1983; Weiss

& Larink, 1991). When bacteria are plentiful in soil, bacteriovorous nematodes

may discharge amino acids in substantial amounts. However, as bacterial

population decrease, nematodes begin to starve, and protein catabolism for

116  

maintenance energy requirements leads to increased ammonium excretion by

nematodes (Anderson et al., 1983). Nitrogen content appears to be an important

measure of potential microbial activity and, subsequently, the rate of

decomposition (Neely et al., 1991).

Prior to the initiation of research on C. elegans, other than the activities of

a few taxonomists, most studies on soil nematodes centered on the biology and

management of those that cause damage to higher plants. A milestone in the

ecology of free-living soil nematodes was the seven-year study in Denmark by

Overgaard Nielsen (1949) on nematode faunae of different soils, their

physiological ecology and even their ecosystem services. Further notable

ecological contributions emerged in the 1970s and 1980s. Centres of ecological

study on nematodes developed in Sweden (Sohlenius, 1973), Poland (Prejs, 1970;

Wasilewska, 1970), Italy (Zullini, 1976), and Russia (Tsalolikhin, 1976). In the

USA, there was a surge of activity in soil ecology at the National Resource

Ecology Laboratory in Colorado Springs, led by Coleman and others (Yeates &

Coleman, 1982), and similar activity at the Institute of Ecology of the University

of Georgia, led by Crossley and colleagues (Stinner & Crossley, 1982). In the

same time period, Yeates was developing a very productive programme on the

ecology of soil nematodes in New Zealand (Yeates, 1979). A significant

contribution was the publication of the PhD research of Ingham, with its

accompanying review of preceding studies, in which the functional significance

of bacterivore and fungivore nematodes was established by the demonstration

that their excretion of nitrogen in excess of structural and metabolic needs

stimulated plant growth (Ingham et al., 1985).

117  

The ecological classification of terrestrial nematodes has usually been

based on their feeding biology (trophic functions) and on the life strategies viz.

colonizers vs persiters (Bongers, 1990). Yeates et al., (1993) categorized

terrestrial nematodes into eight feeding groups, but most ecologists classify soil

nematodes into five feeding groups as discussed below (Yeates, 1998, Yeates &

Bongers, 1999).

1. Plant feeding/herbivores: - Nematodes feeding on vascular plants use a

tylenchid stylet/ dorylaimoid stylet or onchiostyle. They may be further

categorised on the habit of feeding an area of plant on which they feed.

2. Hyphal feeding/Fungivores:- Nematodes in this category puncture fungal

hyphae by a stylet with narrow lumen.

3. Bacterial feeding/bacteriovores:- This category includes species that feed

on any prokaryotic food source, through a narrow or broad stoma. They may

also ingest other types of food. Soil stages of parasites of vertebrates and

invertebrates are also included in this category.

4. Predators:- Feed on other nematodes or small invertebrates such as rotifers

and enchytraieds. They may be either ingestors or piercers.

5. Omnivores:- They appear to feed on a range of food source. It is usual to

restrict the term omnivore to some dorylaimids.

Within the five groups, strong relationship are found between herbivores

and fungal feeders, between herbivores and predators and between fungal feeders

and predators (Yeates et al.,1993 and Gomes et al., 2003). Degree of correlation

between different trophic groups is calculated by using the Karl Pearson’s

coefficient of correlation. It is used to measure the degree of relationship between

118  

two or more variables, which is based on arithmetic mean and/or standard

deviation.

The idea of using ecological indices as indicators of ecosystem quality

(e.g. diversity, stability, and resilience) has received increased attention over the

last decade. Indices may be useful tools because they not only provide

quantitative means to characterize an ecosystem, but also to compare different

ecosystems (Ferris et al., 1996; Porazinska et al.,1998; Yeates & Bird, 1994; and

Yeates et al.,1997). Based on the densities of genera and trophic groups,

ecological indices of the nematode community are derived. The Shannon-Weaver

diversity index (Shannon & Weaver, 1949) is used to compare diversity of either

genera or trophic groups, and Simpson index (1949) is used to compare either

generic or trophic dominance. Maturity index Bongers (1990) and Yeates (1994)

is a semi-quantitative measure since it takes into consideration biological and

ecological characteristics of individual nematode species comprising a particular

community and these indices seems to offer better prospects for detecting and

sufficiently illustrating changes in the soil environment. The maturity index is

calculated as a weighted mean of the c-p values of nematodes in the sample.

Bongers (1990) defined two types of maturity indices: Maturity index (MI) which

includes nematodes belonging to all feeding types except herbivores, and Plant

parasitic index (PPI) which includes herbivores only. In general, the higher a

maturity index value, the more mature and stable the ecosystem. Based on effects

of the geographic distribution of nematodes, nematode feeding types, soils and

succession. Bongers et al., (1995) demonstrated that under certain conditions the

PPI and MI behave in opposite manners and suggested that an increase in the

119  

PPI/MI ratio might reflect ecosystem enrichment. It has been found that PPI/MI

is an effective indicator of enrichment in agro-ecosystems (Ferris et al., 2001).

The combination of nematode feeding groups and cp scaling into

functional guilds have developed nematode faunal analysis into a powerful tool

which can be used as an indicator of soil health and soil food web conditions.

Various functional guilds of nematodes have been described to compute

Enrichment index (EI) and Structure index (SI). Enrichment index is based on

expected responsiveness of the opportunistic guilds (Ba1) to the food resource

enrichment. Thus, EI describes whether a soil ecosystem is nutrient enriched

(high EI) or depleted (low EI). The SI represents an aggregation of functional

guilds with cp values ranging from 3-5. SI describes whether soil ecosystem is

structured/ matured (high SI) or disturbed/ degraded (low SI). In addition to these

indices, Channel index (CI) is also calculated, which is the percentage of

fungivores among the total of fungivores and opportunistic bacteriovores to

describe the dominant decomposition channels in the food web. The CI also

provides a mean of tracking succession between fungivore and bacteriovore

nematodes as organic resources are supplied and depleted in agricultural systems

(Ruess & Ferris, 2002). Decomposition rates of readily degraded materials in

bacterial pathways are expected to be faster than that in fungal pathways where

materials may be more complex. Due to the similarity of C/N of fungi and

fungivore nematodes, mineralization rates in fungal channels is slower than those

in bacterial channels where there is greater difference between C/N ratios of

predators and prey (Ingham et al., 1985; Ferris et al., 1997; Chen & Ferris, 1999;

Okada & Ferris, 2001). Such analysis provides slightly different information than

120  

other analysis based on biomass or diversity and take into consideration both

descriptive and quantitative information on the soil ecosystem. Further, the

redistribution of bacteria to new food sources by survival of passage through the

nematode intestine is an important accelerator of decomposition process

(Wasilewska et al., 1981; Freckman, 1988) for which fungivore nematodes

probably do not provide an equivalent function in the fungal channel.

Nematode faunal analysis is evolving as a powerful bioindicator of the

soil condition and of structural and functional attributes of the soil food web

(Bongers & Ferris, 1999; Neher, 2001). Recent developments of such analyses

include recognition of an enrichment trajectory and a structure trajectory. The

latter measures the abundance of trophic linkages in the food web and the

probability of regulatory effects on opportunist populations through exploitation

and competition. The enrichment trajectory reflects supply-side characteristics of

the food web and the increase in the primary consumers of incoming organic

material (Ferris et al., 2001). Food webs become enriched when disturbance

occurs and resources become available due to external input, organism mortality,

turnover, or favorable shifts in the environment (Odum, 1985; Van Veen &

Kuikeman, 1990). The enrichment-opportunist bacteriovore nematode guild

includes species in the families Rhabditidae, Panagrolaimidae and Diplogastridae

(Bongers & Ferris, 1999; Ferris et al., 2001). They are classified as cp-1

organisms, characterized by short generation time, small eggs and high fecundity,

in the colonizer-persister scale of Bongers (1990). They appear to feed

continuously in the enriched media and then form metabolically suppressed

dauerlarvae as resources are diminished. As microbial blooms fade, enrichment-

121  

oppurtunist microbivores may be replaced by general-opportunist with

specialized morphological, physiological and behavioral adaptations for more

deliberate feeding on less-available resources. The general-opportunist

nematodes, classified as cp-2, are predominantly bacterial scavengers in the

Cephalobidae and fungal-feeders in the Aphelenchidae, Aphelenchoididae and

Anguinidae. Increased abundance of fungal-feeding opportunists occurs when the

available organic pool is conductive to fungal decomposition as, for example,

when complex organic material becomes available in the soil or when fungal

activity is enhanced under conditions less favorable for bacterial decomposition

(Eitminaviĕūté et al., 1976; Wasilewska et al., 1981). In fact, nematodes in the

general-opportunist guild commence to increase with the initial enrichment, but

at slower rate than the enrichment opportunists so that they become

successionally predominant as the latter guild is declining (Bongers, 1990; Ferris

et al., 1996b, 2001; Bongers & Bongers, 1998; Bongers & Ferris, 1999; Chen &

Ferris, 2000).

Studies are being carried out throughout the world on various aspects of

nematode ecology. Most of the studies are concentrating on the impact of heavy

metals on nematode assembleges and secondary succession of nematode guilds.

Zhang et al. (2007) studied responses of nematode assemblages to Cu and Zn

pollution on corn fields near a copper smelter in Northeast China. Dechang et al.

(2009) & Tomar et al. (2009) studied effects of heavy metals on nematode

functional guilds in agro-ecosystems of Shenyang, Liaoning province, China and

reported that the concentrations of lead were most significant at distance of 20 m

from the highway, and than concentration gradually decreased to further

122  

distances. Cheng & Grewal (2009) studied dynamics of soil food web under

urban landscape and reported that anthropogenic activities resulting in the loss of

top soil can have profound effect on the structure of soil food web, which may

severely limit its capacity to support optimal nutrient cycling. Mahran et al.

(2009) studied response of nematode communities to hog manuring and reported

that hog manuring is effective in killing plant parasitic nematodes. Hánèl (2010)

studied succession of nematodes in agro-ecosystems and compared it with

abandoned fields in South Bohemia. Biodiversity and trophic structure of soil

nematode communities in subtropical ecosystems was studied by Bierdermann &

Boutton (2010). Their study mainly focused on nematode responses to woody

plant encroachment in urban areas. They reported that energy flow through

nematode food webs in grasslands appear relatively diversified and SI indicated

that nematode communities within old clusters were more simplified than those

in grassland due to reduction in densities of omnivores and predators. Soil

nematode communities of a banana planted agro-ecosystem were studied by

Tabarant et al. (2011). They concluded that plant residue and bagasse which are

mainly composed of cellulose and lignins which are difficult to decompose.

These chemicals mainly favor fungal decomposition pathways and permitted

development of carnivorous nematodes and thus increasing channel index. Park

et al. (2011) studied effects of heavy metal contamination in abandoned mines.

They examined two areas one with heavy metal infection from mines and another

control area which had no infection and found that diversity of nematodes was

less in contaminated area as compared with non contaminated area. Liu et al.,

(2011) studied effects of biological crusts on soil nematode communities and

123  

found that nematode abundances, generic richness and food web based indices as

EI and SI positively correlated with different crust ages.

The nematodes have been widely studied in India in contrast of plant

parasites and control of nematode menace in agro-ecosystems. Various

researchers have used nematodes for studying effects of organic amendments in

field and micro-plot experiments. Singh (1970) studied control of plant parasitic

nematodes with organic soil amendments. Akhtar (1993, 1999 & 2000) studied

possible relation of organic soil amendments and nematodes. Devi & Das (1998)

studied effects of organic amendments of root knot nematodes. Hassan et al.

(2008 & 2009) studied nematodes of Zea mays and their possible control through

organic amendments. There are some sporadic reports of study of nematode

diversity in different ecosystems. Tomar et al. (2006) reported diversity of

nematodes at a Mango orchard in Aligarh. Baniyamuddin et al. (2007) studied

functional diversity of nematodes of natural forests in Arunachal Pradesh. Tomar

& Ahmad (2009) studied nematode community in a natural woodland of Aligarh

region, and reported it to be a stable ecosystem on the basis of maturity and plant

parasitic indices.

The aim of the present study was to investigate nematode communities

and temporal changes in the nematode fauna of two different habitats (crop field

and natural wasteland), for a period of one year. These two habitats were located

at a distance of 6 Kms from each other. Specifically, population dynamics, faunal

analysis, and community composition of soil nematodes have been studied to

assess the role of nematodes as indicators of soil condition.

124  

Materials &

Methods

Site description: - The experimental sites a) Crop field (CF) and b) Wasteland

(WL) were selected on the basis of differences in their vegetation and soil

disturbance. Both the sampling sites were located in Aligarh district. The climate

of the region, in general the blocks in the west are drier as compared to those in

the east. The temperature rises as high as 44.6˚C during summer and drops down

to as low as 4.8˚C during winters. The mean maximum and mean minimum

temperature of district Aligarh is 26.7˚C and 15.5˚C respectively. Monsoon starts

in July and runs to September. While in winter season, the region receives very

few showers. The mean annual rainfall of the district is 434 mm, mean relative

humidity 65%. Thus the Climate of the district Aligarh is Semi-Arid. Served by

numerous rivers, rivulets and canals of the Ganga. Few rivers like Karwan,

Rutba and Kali pass through the district but remain almost dry except during

rainy season.

Site a):- The crop field situated about 14 Kms from Aligarh city, on Aligarh –

Moradabad highway (27° 57′ N, 78° 10′ E) was selected. The field was cultivated

under annual conventional cropping system whereby wheat was the only crop

sown during the sampling time with fallow periods in between. During sampling

crop was at different stages of development. Organic amendments were added to

the crop field in form of manures during September-October. Chemical fertilizer

mainly NPK were added to field during December-January

Site b) :- This site was natural wasteland, more than two decades old, situated

about 8 Kms from Aligarh city on Aligarh – Moradabad highway (27° 55′ N, 78°

54′ E) was selected for sampling. The wasteland covers more than two sq. Km

125  

area on either side of highway. Wasteland usually remained dry and bare during

most of the time except monsoon. During monsoon most parts of the area were

covered by grasses.

Sampling

Soil samples from crop field were collected following the growth pattern

of the crop, simultaneously samples were also collected from wasteland. In

Aligarh district monsoon starts in July and runs to September. Wheat was sown

during the month of October/November and harvested during February/March.

Sampling was undertaken on eight occasions from June 2008 to April 2009 at

different stages of development of wheat crop including the fallow periods before

and after the cropping period. Each soil sample consists of five cores (1 cm2

cross sectional area) from a depth of 0-10 cm. All the samples were collected

windward in N-W direction. Samples were tagged, stored in sealed plastic bags

and brought to laboratory for further processing. For sampling from both the

areas a diagonal transect was selected and samples were collected from the same.

Processing of soil samples

About 100 cc of soil from each sample was processed by Cobb (1915)

sieving and decantation and modified Baermann’s funnel technique as discussed

earlier in Part A.

Isolation and Killing & Fixation of Nematodes

The isolation, killing and fixation of nematodes were done by the same

process as it was done in Part A.

126  

Counting of Nematodes

Population count of nematodes was made using Syracuse counting dish.

The suspension was made homogenous by bubbling with pipette thoroughly

before taking 2 ml of nematode suspension in the dish for counting. Counting of

each sample was done three times and mean was obtained. The final population

was obtained by multiplying final quantity of nematode suspension (50 ml) with

mean number of nematodes counted and dividing by the quantity of suspension

used for counting (2 ml).

Identification

Mass slides containing about two hundred nematodes per sample were

prepared for identification. Identification up to generic level was done mainly

using Goodey (1963); Jairajpuri & Khan (1982); Andrássy (1984, 2005), Siddiqi

(1986), Jairajpuri & Ahmad (1992); Ahmad (1996). Trophic group were allocated

according to Yeates et al. (1993) and cp groups were assigned after Bongers

(1990).

Data Analysis

Nematode diversity was described using the univariate measures of the

Shanon index calculated at genus level (H’) and multivariate analysis was

performed by ANOVA using statistical programme SPSS. Shanon’s diversity

(H’) was calculated by SPECDIVE. Nematodes were assigned to five main

trophic groups (bacteriovores, fungivores, herbivores, omnivores and predators)

after Yeates et al. (1993). Maturity index (MI) was calculated to estimate the

relative state of two ecosystems studied. Trophic diversity was calculated by the

127  

trophic diversity index, (TDI) (Heip et al., 1988). Structure index (SI) and

enrichment index (EI) were calculated to determine the relative stability of the

ecosystem studied. Nematode channel ratio was calculated to reflect differences

in the mineralization of dead and live plant tissues. (Wasilewska, 1994). In all the

above mentioned indices, nematode families were allocated cp scale according to

their perceived life history strategy.

Detailed description of the formulae used are given below

Shannon’s diversity (H′) = −Σ (pi ln pi)

Maturity Index (MI)

n

iifiVMI

1.

Where Vi= cp value of the ith taxon.

f(i) the frequency of that taxon in a sample

* Maturity index (MI) is calculated as the weighted mean of the individual

cp value.

Plant Parasitic index (PPI)

XiPPiXiPPI /

Where, Ppi = PP value assigned to taxon i according to Bongers (1990).

Xi = abundance of taxon i in the sample.

128  

Nematode Channel Ratio (NCR)

FB

BNCR

Where, B = Total abundance of Bacterial feeding nematodes

F = Total abundance of Fungal feeding nematodes.

Enrichment index (EI) = (e/e+b) x100

Structure index (SI) = (s/s+b) x100

where e, b & s are sum products of assigned weights and number of

individuals of all genera (Table 1,2).

Trophic Diversity index (TDI) = 1 ⁄ ∑pi²

where pi² is the proportional contribution of ith trophic group.

129  

Table 1:- Nematode functional guilds in different Food web conditions.

Basal (b) Structured (s) Enriched (e)

Ba2- Cephalobidae Ba3- Prismatolaimidae Ba1- Rhabditidae,

Panagrolaimidae

Fu2- Aphelenchidae,

Aphelenchoididae

Anguinidae.

Fu3- Diptherophoridae

Fu4- Leptonchidae

Pr2- Aphelenchid Carnivores

Pr3- Tripylidae

Pr4- Mononchidae

Pr5- Discolaimidae

Om4- Dorylaimidae

Om5- Thornenematidae,

Qudsianematidae

The numbers used in the table denotes the assigned c-p value to the trophic groups as follows:

Ba- Bacteriovores

Fu- Fungivores

Pr- Predators

Om- Omnivores

 

130  

Results

Nematode Diversity

During the present course of study a total of 50 genera belonging to 10

orders and 30 families were encountered from the crop field (CF) while 46 genera

belonging to 8 orders and 25 families occurred in the wasteland (WL). The

number of genera varied from 13 to 23 per sample in crop field while in

wasteland it ranged from 7 to 21 per sample. In terms of abundance the number

varied from 105 to 1178 individuals in crop field and 106 to 568 in wasteland per

100 cc of soil. Acrobeloides was the most abundant genus in crop field while

Dorylaimellus was the most abundant genus in the wasteland.

In the crop field, in terms of number of genera (Fig. 1, A) the Order

Dorylaimida was most frequent (30%) with 15 genera under 8 families, followed

by Rhabditida (22%) with 11 genera under 4 families, Tylenchida (20%) with 10

genera under 6 families, Araeolaimida (8%) with 4 genera under 3 families,

Aphelenchida (6%) with 3 genera under 3 families, Enoplida (4%) with 2 genera

under 2 families & Monhysterida (4%) represented by 2 genera under 1 family,

while Alaimida (2%), Diptherophorida (2%) and Chromadorida (2%) were

represented by 1 genus each. However, in wasteland, (Fig. 1, C) Order

Dorylaimida (32%) was most prevalent with 7 families representing 15 genera

followed by Tylenchida (22%) with 10 genera under 6 families, Rhabditida

(22%) with 4 families representing 10 genera, Aphelenchida (7%) and

Chromadorida (7%) were represented by 3 genera each under 3 families and & 1

family respectively, while Araeolaimida (4%) and Monhysterida (4%) were

represented by 2 genera each under 2 families and 1 family respectively and

Enoplida (2%) was the least prevalent with single genus.

131  

In terms of number of individuals (Fig. 1, B), Rhabditida (44%) was most

abundant, followed by Tylenchida (19%), Dorylaimida (12%), Aphelenchida

(11%), Araeolaimida (8%), Enoplida (2%), Alaimida, Chromadorida,

Monhysterida and Diptherophorida (1% each) in crop field. While in wasteland

(Fig. 1, D) Rhabditida (33%) was most abundant, followed by Dorylaimida

(27%), Aphelenchida (11%), Tylenchida (10%), Chromadorida (9%),

Araeolaimida (5%), Enoplida (4%) and Monhysterida (1%).

Trophic diversity

In the crop field (Fig. 2, A), bacteriovores constituted the most dominant

group in terms of number of genera and abundance and were represented by 20

genera. This was followed by herbivores, fungivores, omnivores and predators,

which were represented by 9, 8, 7 & 6 genera respectively. In terms of number of

individuals (Fig. 2, B) bacteriovores (58%) was the most abundant group,

followed by fungivores (21%), herbivores (13%), omnivores (5%) and predators

(3%). The trophic diversity index (TDI) of the area ranged from 1.03-1.25

(1.1±0.07). Among bacteriovores the genus Acrobeloides was most dominant

while the genera Hoplolaimus, Aphelenchus, Moshajia and Discolaimus were

most dominant among herbivores, fungivores, omnivores and predators

respectively. Least dominant genera among bacteriovores, herbivores, omnivores,

fungivores and predators were Drilocephalobus, Hemicriconemoides,

Thornenema, Leptonchus and Tripyla respectively (Table 2). Bacteriovores,

fungivores and herbivores were present in all samples while omnivores and

predators were absent from two samples each. In the crop field (Fig. 3) all

132  

nematode population remained relatively low from June to December. Thereafter

the bacteriovores increased in numbers with a peak population in March followed

by a sharp decline. The fungivores followed a somewhat similar pattern but the

population remained comparatively low. All other groups showed peak

population in January but their number was very low.

In the wasteland (Fig. 2, C) also bacteriovores constituted the most

dominant group in terms of number of genera and abundance and were

represented by 18 genera. This was followed by herbivores with 10 genera,

omnivores with 7 genera, fungivores with 6 genera and predators with 5 genera.

The bacteriovores (51%) was the most abundant group in terms of number

followed by fungivores (29%), herbivores (11%), omnivores (6%) and predators

(3%) (Fig. 2, D). The trophic diversity index (TDI) of the area ranged from 1.05-

1.23 (1.12±0.06). Among bacteriovores, the genus Acrobeles was dominant,

while the Ditylenchus, Moshajia, Dorylaimellus and Seinura were most dominant

among herbivores, omnivores, fungivores and predators respectively. Least

dominant genera among various trophic groups were Stegellata, Psilenchus,

Tylencholaimus, Epidorylaimus and Discolaimoides (Table 3). All the samples

contained bacteriovores and fungivores, while herbivores were absent in one

sample and omnivores and predators were not present in four and five sample

respectively. In the wasteland (Fig. 3), population of all groups except herbivores

remained uniform from June to October, dipped in December and peaked of in

January followed by a rapid decline thereafter. At the peak population

bacteriovores were in maximum number followed by fungivores and omnivores.

The herbivore population remained relatively low and showed a peak in October.

133  

Nematode Community Dynamics

The diversity of nematode fauna in agroecosystems and their relationships

to soil processes suggests that they are potential bioindicators. However, the

effects of plants, soil types and nematode biogeography mean a ‘functional

group’ may be a better indicator than particular nematodes. Permanent grassland

may be regarded as providing a baseline for nematode diversity in a given soil.

The relative abundance of fungal-feeding and bacterial-feeding nematodes serve

as sensitive indicator of management changes (Yeates & Bongers, 1999). For

assessing the community dynamics and role of nematodes in the agroecosystems,

various indices such as Shannon’s diversity index (H’), Maturity index (MI)

including plant parasitic families, Maturity index 2-5 (MI25, excluding Ba1

functional guild), Plant parasitic index (PPI), Nematode channel ratio (NCR) and

PPI/MI were calculated. The percent abundance of cephalobids, tylenchids,

dorylaims and other nematodes were also obtained.

Food web diagnostics of the ecosystem was studied in terms of

Enrichment index (EI), Structure index (SI) and Basal index (BI) following the

weighted faunal analysis concept of Ferris et al. (2001).

Shannon’s diversity index (H’) in crop field was found to be 2.21–2.73

(2.45±0.19) and in wasteland it ranged from 1.88–2.54 (2.17±0.22). The maturity

index (MI) ranged from 2.1–2.59 (2.35±0.18) in crop field and 2.36–3.64

(2.9±0.41) in wasteland. MI25 ranged from 2.13–2.59 (2.4±0.18) and 2.37–3.66

(2.91±0.41) in crop field and wasteland respectively. The plant parasitic index

(PPI) for the crop field varied from 2.21–3.19 (2.73±0.33) while it was 2.0–3.0

134  

(2.65±0.41) for wasteland. Nematode channel ratio (NCR) was found to be 0.61–

0.94 (0.76±0.11) and 0.49–0.8 (0.63±0.1) and the values for PPI/MI were 1.01–

1.38 (1.16±0.13) and 0.72–1.28 (0.99±0.21) for crop field and wasteland

respectively (Table 4 & 5). Comparison of crop field samples for indices revealed

that MI was almost constant for all sampling times, while PPI was highest during

June which gradually decreased till December (i.e. growth phase) and than it

increased gradually. NCR also was almost constant throughout. In wasteland MI

showed a gradual increase till December and then gradually decreased, while PPI

and NCR were almost constant for the sampling times (Table 4 & 5, Fig. 4).

The enrichment index (EI) ranged from 13.5–41.1 (26.5±9.8) and 5.2–

38.9 (17.9±10.6) and the structure index (SI) was found to be 22.7–64.2

(47.7±15.8) and 43.3–90 (70.5±15) in the crop field and wasteland respectively.

Basal index (BI) varied from 31.47–68.9 (43.8±13.08) in the crop field and 9.76–

49.3 (26.3±12.15) in the wasteland (Table 4 & 5). Comparison of food web

indices for crop field indicated that BI was highest during December (i.e. growth

phase) showing a linear spline, while the values for SI gradually increased with a

sudden decrease in December. The EI values also followed same pattern as of SI.

In wasteland SI gradually increased till December and then remains constant

while BI gradually decreased till December and increased constantly for the next

sampling times. EI shows a sudden dip in the month of October and then it

gradually increased till the end of sampling (Table 4 & 5, Fig. 5).

The abundance of cephalobids per sample ranged from 32.2-58.6%

(42.5±9.4) in crop field and 14.4-44.6% (31.8±9.2) in wasteland while of

tylenchids it ranged from 8.9-39.8% (19.4±9.8) in crop field and 1.4-22.3%

135  

(10.3±6.6) in wasteland. The dorylaims abundance varied from 1.9-19.5%

(11.7±6.2) and 12.6-44.9% (27.2±10.1) and others groups from 14.7-38.2%

(26.4±8) and 12.3-36.3% (30.7±8.3) in crop field and wasteland respectively

(Table 4 & 5, Fig. 6).

In crop field (Table 6), population of dorylaims show very high degree of

positive correlation with MI and SI (Fig. 7, A & B), and very significant negative

correlation with BI (Fig. 7, C). With all other indices dorylaims show either

negative correlation or almost no correlation. Population of tylenchids show low

level of positive correlation with PPI/MI ratio and to certain level with PPI (Fig.

7, D), while some degree of negative correlation with MI and SI. Population of

cephalobids show a low level of positive correlation with PPI and low level of

negative correlation with MI while almost no correlation was found with EI ans

SI. Almost no correlation was found with MI while it was negatively correlated

with PPI, EI and SI.

In Wasteland (Table 6), population of dorylaims showed very high degree

of positive correlation with MI and SI (Fig. 8, A & B) while significant negative

correlation was found with PPI/MI ratio and BI. Population of tylenchids show

some degree of positive correlation with MI, PPI and SI while they are negatively

correlated to some degree with EI, BI and PPI/MI ratio. Population of

cephalobids showed high degree of negative correlation with MI (Fig. 8, C) and

SI while significant positive correlation was found with H′ and PPI/MI ratio and

upto certain level with PPI, however, there was almost no correlation was found

with EI. Other nematodes show some degree of positive correlation with EI while

certain level of negative correlation with MI, PPI and SI was observed.

136  

Significant negative correlation was also observed between population of

dorylaims and cephalobids (Fig. 8, D).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

137  

Table 2: Population structure of soil inhabiting nematodes of crop field  

Genera N* AF% MD RD%

Bacteriovores

Acrobeles 27 88.89 7.95 3.60

Acrobeloides 40 133.33 35.45 16.05

Alaimus 8 27.78 1.48 0.67

Cephalobus 37 122.22 23.55 10.66

Cervidellus 5 16.67 0.63 0.28

Chiloplacus 40 133.33 21.53 9.75

Chromadora 8 27.78 2.03 0.92

Chronogaster 12 38.89 3.05 1.38

Drilocephalobus 2 5.56 0.15 0.07

Eucephalobus 15 50.00 2.83 1.28

Mesorhabditis 25 83.33 5.25 2.38

Monhystera 7 22.22 2.83 1.28

Monhystrella 3 11.11 0.13 0.06

Panagrolaimus 8 27.78 0.50 0.23

Plectus 27 88.89 3.25 1.47

Prismatolaimus 20 66.67 5.53 2.50

Rhabdolaimus 20 66.67 10.33 4.67

Stegellata 7 22.22 1.15 0.52

Wilsonema 3 11.11 0.25 0.11

Zeldia 15 50.00 1.10 0.50

Fungivores

Aphelenchoides 30 100.00 10.58 4.79

Aphelenchus 33 111.11 11.63 5.26

Basirotyleptus 18 61.11 8.18 3.70

Dorylaimellus 20 66.67 6.20 2.81

Filenchus 3 11.11 0.20 0.09

Leptonchus 3 11.11 0.13 0.06

Tylencholaimus 12 38.89 0.93 0.42

Tylenchus 28 94.44 7.63 3.45

Herbivores

Boleodorus 5 16.67 0.65 0.29

Ditylenchus 25 83.33 8.95 4.05

Helicotylenchus 12 38.89 0.88 0.40

Hemicriconemoides 2 5.56 0.05 0.02

Hoplolaimus 28 94.44 8.75 3.96

Merlinius 5 16.67 0.43 0.19

Pratylenchus 5 16.67 0.40 0.18

Trichodorus 5 16.67 1.03 0.46

Tylenchorhynchus 27 88.89 8.80 3.98

138  

Omnivores

Epidorylaimus 3 11.11 0.08 0.03

Eudorylaimus 8 27.78 1.10 0.50

Latocephalus 3 11.11 0.05 0.02

Moshajia 32 105.56 8.30 3.76

Oriverutus 2 5.56 0.08 0.03

Thonus 8 27.78 0.63 0.28

Thornenema 2 5.56 0.05 0.02

Predators

Aporcelaimellus 10 33.33 0.93 0.42

Aquatides 5 16.67 0.70 0.32

Discolaimus 20 66.67 2.00 0.91

Discolaimoides 8 27.78 0.93 0.42

Seinura 10 33.33 1.73 0.78

Tripyla 2 5.56 0.03 0.01  

*Mean of five replicates

 

 

 

 

 

 

 

 

 

 

 

 

 

 

139  

Table 3: Population structure of soil inhabiting nematodes of wasteland

Genera N* AF% MD RD%

Bacteriovores

Achromadora 3 8.33 1.53 1.09

Acrobeles 32 79.17 5.83 4.17

Acrobeloides 25 62.50 7.48 5.35

Cephalobus 28 70.83 14.15 10.14

Cervidellus 5 12.50 0.20 0.14

Chiloplacus 28 70.83 13.83 9.90

Chromadora 3 8.33 0.58 0.41

Eucephalobus 17 41.67 2.23 1.59

Geomonhystera 3 8.33 0.15 0.11

Mesorhabditis 8 20.83 0.60 0.43

Monhystrella 2 4.17 0.25 0.18

Monochromadora 27 66.67 11.13 7.97

Panagrolaimus 7 16.67 0.65 0.47

Plectus 27 66.67 2.10 1.50

Prismatolaimus 20 50.00 6.18 4.42

Protorhabditis 8 20.83 0.48 0.34

Rhabdolaimus 28 70.83 4.60 3.30

Stegellata 2 4.17 0.15 0.11

Fungivores

Aphelenchoides 35 87.50 7.68 5.50

Aphelenchus 25 62.50 5.88 4.21

Basirotyleptus 5 12.50 0.30 0.21

Belondira 5 12.50 0.95 0.68

Dorylaimellus 40 100.00 24.95 17.87

Tylencholaimus 3 8.33 0.23 0.16

Omnivores

Dorylaimoides 2 4.17 0.10 0.07

Epidorylaimus 2 4.17 0.05 0.04

Eudorylaimus 8 20.83 0.50 0.36

Latocephalus 8 20.83 0.65 0.47

Mesodorylaimus 15 37.50 2.55 1.83

Moshajia 22 54.17 3.85 2.76

Thonus 3 8.33 0.18 0.13

Herbivores

Boleodorus 5 12.50 0.68 0.48

Ditylenchus 17 41.67 2.58 1.84

Helicotylenchus 13 33.33 0.85 0.61

Heterodera 2 4.17 0.90 0.64

Hoplolaimus 12 29.17 1.68 1.20

Merlinius 3 8.33 0.98 0.70

140  

Pratylenchus 12 29.17 5.63 4.03

Psilenchus 2 4.17 0.13 0.09

Tylenchorhynchus 8 20.83 0.55 0.39

Tylenchus 10 25.00 1.08 0.77

Predators

Aporcelaimellus 10 25.00 1.35 0.97

Aquatides 5 12.50 0.23 0.16

Discolaimoides 3 8.33 0.20 0.14

Discolaimus 13 33.33 1.65 1.18

Seinura 15 37.50 1.23 0.88

 

*Mean of five replicates

 

141  

Tab

le 4

: Cha

ract

eris

tics o

f cro

p fie

ld

Ju

ne

Sept

embe

rO

ctob

er

Dec

embe

r Ja

nuar

y Fe

brua

ry

Mar

ch

Apr

il M

ean±

SD

H'

2.24

2.

21

2.63

2.

33

2.73

2.

53

2.34

2.

56

2.45

±0.1

9

MI

2.32

2.

31

2.38

2.

10

2.50

2.

12

2.49

2.

59

2.35

±0.1

8

MI2

5 2.

33

2.42

2.

50

2.13

2.

58

2.16

2.

50

2.59

2.

4±0.

18

PPI

3.19

3.

00

2.83

2.

45

2.56

2.

21

3.00

2.

60

2.73

±0.3

3

PPI/M

I 1.

38

1.30

1.

19

1.16

1.

03

1.04

1.

21

1.01

1.

16±0

.13

EI

26.7

5 26

.19

41.1

4 13

.51

38.2

4 29

.33

15.1

9 22

.04

26.5

±9.8

SI

43.6

2 50

.77

56.5

6 22

.70

60.4

7 25

.59

57.4

4 64

.25

47.7

±15.

8

BI

46.9

2 41

.01

33.9

0 68

.91

31.4

7 56

.11

39.5

6 32

.41

43.8

±13.

08

TDI

1.26

1.

05

1.04

1.

06

1.12

1.

06

1.05

1.

10

1.1±

0.07

NC

R

0.74

0.

81

0.83

0.

94

0.61

0.

74

0.76

0.

64

0.76

±0.1

1

% C

epha

lobi

ds

32.2

6 58

.63

51.1

3 45

.28

36.3

6 37

.06

46.3

2 33

.02

42.5

±9.4

% T

ylen

chid

s 39

.78

13.4

0 13

.15

24.6

7 22

.64

18.9

5 8.

93

13.6

2 19

.4±9

.8

% D

oryl

aim

s 6.

89

13.2

7 12

.33

1.94

19

.51

5.83

17

.00

16.9

2 11

.7±6

.2

% O

ther

s 21

.07

14.6

9 23

.39

28.1

1 21

.48

38.1

6 27

.74

36.4

4 26

.4±8

Tab

le 5

: Cha

ract

eris

tics o

f was

tela

nd

Ju

ne

Sept

embe

r O

ctob

er

Dec

embe

rJa

nuar

y Fe

brua

ry

Mar

ch

Apr

il M

ean±

SD

H'

2.28

2.

08

1.97

1.

88

2.17

2.

06

2.54

2.

39

2.17

±0.2

2

MI

2.36

2.

60

3.23

3.

64

2.91

3.

05

2.72

2.

65

2.9±

0.41

MI2

5 2.

37

2.64

3.

28

3.66

2.

92

3.07

2.

72

2.65

2.

91±0

.41

PPI

3.00

3.

00

2.93

2.

47

2.11

2.

67

2.00

3.

00

2.65

±0.4

1

PPI/M

I 1.

28

1.18

0.

91

0.72

0.

74

0.87

1.

09

1.13

0.

99±0

.21

EI

20.1

6 38

.96

5.21

13

.74

15.2

6 26

.44

13.6

0 9.

92

17.9

±10.

6

SI

43.2

9 57

.67

83.2

4 90

.02

72.7

4 80

.91

67.7

2 68

.12

70.5

±15

BI

49.3

3 30

.52

16.6

1 9.

77

25.4

3 17

.56

30.6

9 30

.89

43.8

±13.

1

TDI

1.08

1.

15

1.14

1.

24

1.10

1.

15

1.09

1.

05

1.12

±0.0

6

NC

R

0.70

0.

54

0.59

0.

49

0.65

0.

58

0.68

0.

80

0.63

±0.1

% C

epha

lobi

ds

44.5

9 32

.31

33.4

1 14

.42

26.5

6 26

.93

38.3

0 37

.69

31.8

±9.2

% T

ylen

chid

s 6.

46

12.8

9 22

.37

15.8

5 6.

90

6.78

1.

42

9.82

10

.3±6

.6

% D

oryl

aim

s 12

.63

20.8

7 31

.91

44.9

4 31

.69

30.5

8 27

.25

17.6

3 27

.2±1

0.1

% O

ther

s 36

.31

33.9

4 12

.31

24.7

9 34

.85

35.7

1 33

.03

34.8

6 30

.7±8

.3

Crop field

H MI PPI PPI/MI EI SI BI % D % T % C % O

H 1

MI .366 1

PPI -.549 .364 1

PPI/MI -.793* -.197 .841** 1

EI .643 .181 -.036 -.143 1

SI .342 .967** .456 -.081 .327 1

BI -.458 -.902** -.374 .133 -.534 -.964** 1

% D .433 .918** .242 -.283 .294 .930** -.913** 1

% T -.244 -.347 .144 .375 .042 -.401 .378 -.516 1

% C -.326 -.175 .270 .378 -.009 .020 .009 .019 -.539 1

% O .347 -.085 -.687 -.687 -.271 -.258 .239 -.171 -.190 -.534 1

Wasteland

H MI PPI PPIMI EI SI BI % D % T % C % O

H 1

MI -.718* 1

PPI -.255 -.262 1

PPIMI .588 -.863** .514 1

EI -.077 -.426 .250 .375 1

SI -.617 .937** -.208 -.818* -.403 1

BI .664 -.938** .252 .848** .285 -.988** 1

% D -.614 .954** -.512 -.911** -.346 .877** -.907** 1

% T -.758* .565 .492 -.288 -.247 .555 -.527 .371 1

% C .723* -.869** .330 .869** .067 -.794* .855** -.899** -.355 1

% O .542 -.641 -.133 .370 .542 -.623 .569 -.509 -.848** .262 1

** Correlation is significant at the 0.01 levels * Correlation is significant at the 0.05 levels

% D - % Dorylaims; % T - % Tyelnchids; % C - % Cephalobids; % O - % Others

Table 6: Correlation coefficient between different indices and nematode groups in crop field and wasteland

144  

Fig.1: Ordinal diversity and abundance of nematodes in a Crop field (A & B) and wasteland (C & D)

145

A

B

C

D

Fig. 2: Trophic diversity and abundance of nematodes in a crop field (A & B) and wasteland (C & D)

146

C

D

B

A

Fig. 3: Population structure of different trophic groups during variuos sampling times

147

Fig. 4: Relation between different indices (MI, PPI, NCR) in crop field and wasteland

148

Fig. 5: Relation between different indices (EI, SI, BI) in crop field and wasteland

149

Fig. 6: Population structure of different nematode groups during various sampling times

150

Fig.7: Relationships between different nematode groups and indices in crop field

151

A

% Dorylaims

MI

0.2 3.7 7.2 10.7 14.2 17.8 21.32.06

2.15

2.25

2.35

2.44

2.54

2.64B

% Dorylaims

SI

0.2 3.7 7.2 10.7 14.2 17.8 21.318.54

26.85

35.16

43.48

51.79

60.10

68.41

D

% Tylenchids

PPI

5.8 12.0 18.2 24.4 30.5 36.7 42.92.11

2.31

2.50

2.70

2.90

3.09

3.29

C

% Dorylaims

BI

0.2 3.7 7.2 10.7 14.2 17.8 21.327.73

35.22

42.70

50.19

57.68

65.16

72.65

y = 2.04+2.60xr = 0.918

y = 2.00+2.36xr = 0.931

y = 6.62-1.91xr = 0.913

y = 2.63+4.85xr = 0.144

A

% Dorylaims

MI

9.4 15.9 22.3 28.8 35.2 41.7 48.22.23

2.49

2.74

3.00

3.26

3.51

3.77B

% Dorylaims

SI

9.4 15.9 22.3 28.8 35.2 41.7 48.238.62

47.96

57.31

66.66

76.00

85.35

94.70

D

% Dorylaims

% C

epha

lobi

ds

9.4 15.9 22.3 28.8 35.2 41.7 48.211.40

17.44

23.47

29.50

35.54

41.57

47.61C

% Cephalobids

MI

11.4 17.4 23.5 29.5 35.5 41.6 47.62.23

2.49

2.74

3.00

3.26

3.51

3.77

y = 4.11-3.82xr = 0.869

y = 5.41-8.23xr = 0.0.899

y = 3.41+1.33xr = 0.898

y = 1.85+3.84xr = 0.954

Fig. 8: Relationships between different nematode groups and indices in wasteland

152

Discussion

Soil fauna have strong relationships with fundamental ecosystem

processes such as decomposition and nutrient cycling, and interactions with the

microbial community, plant growth and pedogenesis and thus can serve as useful

indicators of ecosystem conditions (Parmellee, 1994; Auerswald et al., 1996;

Reddy et al., 1996; Anderson & Sparling, 1997). The nematode diversity of agro-

ecosystems offers many possibilities for use as biological indicators of

agricultural practices, soil characteristics and the degree of conservation of soils.

Whole nematode populations, represented by the structure of functional groups

probably represent, in many cases, better indicators than those derived from any

species in particular (Yeates & Bongers, 1999).

Soil nematodes have been found to regulate the bacterial and fungal

populations and thus are intimately associated with the cycling of major nutrients

in soils (Ingham et al., 1985) and a more positive view of the role of nematodes in

soil processes has been adopted (Yeates, 1987). There are thus apparently

significant possibilities for the use of nematode populations and diversity as

indicators of overall soil condition. Nematode communities are sensitive to

chemical and physical disturbances in ecosystem. These disturbances can alter

nematode communities in qualitatively different ways (Fiscus & Neher, 2002). A

higher percentage of dorylaims in the wasteland (27%) as compared to the crop

field (12%) clearly indicates that the wasteland soil is less disturbed as may be

expected. Cropping on the other hand always involves ploughing and/or tilling

together with addition of fertilizers, organic matter and pesticides/weedicides.

The dorylaims appear to be susceptible to these activities as also shown by

Thomas (1978) and Sohlenius & Wasilewska (1984). Hence, the sensitivity of the

153  

dorylaims is a good indicator of soil disturbance (Neher, 2001).

In this study Acrobeloides was the most abundant genus in crop field and

confirms the work of Yeates & Bird (1994) and Gomes et al. (2002) where it was

found that cephalobids were the most abundant bacterial feeders present in

cropping systems.

Agro-ecosystems are generally characterized by periodic disturbances and

tillage, cultivation, use of pesticides and fertilizers impede natural succession.

Although each of these disturbances have specific effects but mainly results in a

decrease of diversity (Yeates & Bongers, 1999). Ploughing stimulates

mineralization and results in increase in the number and dominance of

opportunistic taxa. Pesticides influence soil biota directly or indirectly via plants.

It is generally accepted that undisturbed systems have more diverse communities

of soil organisms (Kandji et al., 2001). Plots with more ground cover vegetation

often support the most diverse assemblages of nematodes, possibly as a result of

the greater heterogeneity of resources added through the return of residues and

root exudates (Ou et al., 2005).

Bacteriovores in the crop fields showed two phases of population increase.

A small increase during December-January and a big increase during February-

March. One factor that may be responsible for the increase in the population of

these nematodes in the early part is farmyard manure that was added to the fields

before sowing. However the greater increase in the later (post-harvest) part of the

study may also be due to organic matter. This becomes available because of

decaying roots and rotting stubble after the harvest and could be the likely cause

of this second peak. Organic amendments are known to increase the population of

154  

the Ba1 group of nematodes and maintain them till the material is exhausted

(Bongers & Ferris, 1999; Porazinska et al., 1999). Manuring is also known to

bring about a sudden increase in the population of bacterial feeders (Dmowska &

Kozlowska, 1988). The sharp decline of bacteriovorous nematodes during March-

April may also be due the organic matter; although this time acting perhaps

differently. Depleted organic matter, of the decaying roots and stubble, could

result in depleted bacterial populations and hence a reduced food source for the

bacteriovores resulting in their decline. Bulluck et al., (2002) have shown that

when food supply is exhausted bacteriovores populations also decline. Although

temperature records were not maintained, there is a relatively big increase in

maximum temperatures from February to April, and it may not be improper to

speculate that this could lead to drying of the top soil and also a decline in

nematode populations.

The herbivore population of the crop field varied little during the period of

study except for a small peak in January. This coincides with the maturing of the

crops and as such represents a period of an abundant food source brought about

by the proliferated root system and seems to be the most likely cause of the peak.

Increase nutrient availability is known to increase herbivore populations through

an enhanced food resource (Pattinson et al., 2004). Fertilizer application after

sowing in October did not seem to affect nematodes as all trophic group

populations remained relatively unchanged till December. Further, the peak of

the herbivores coincided with peak or rising populations of the other groups. This

contrasts with findings of Yeates (1982), Sohlenius & Bostrom (1986), Edwards

(1989) and Hoyvönen & Hühta (1989) who observed an increase in the plant

155  

parasites and bacterial feeders after fertilizer application in cultivated soil or a

decrease of fungal feeders and omnivores (Sohlenius & Wasilewska, 1984;

Sohlenius & Bostrom, 1986; Sohlenius, 1990).

In the wasteland, populations fluctuated little over most part of the year

except from December to February when a small decline was followed by a peak

in January in the case of bacteriovores, fungivores and omnivores. Predator

populations remained at low levels throughout the year while the herbivores

showed a peak in October. The increase of herbivores seems to be related to the

grasses that grow in the wastelands after the rains. As winter sets in, this

vegetation begins to wither and die and enriches the soil with organic matter that

may be responsible for the peak populations of the bacteriovores, fungivores and

the omnivores. In grasslands used by grazing animals, high populations of

bacterial feeders were attributed to high level of food resource made available by

addition of organic matter in the form of dung (Freckman et al., 1979).

Shannon’s diversity index (H’) reflects diversity of nematodes in an

ecosystem. Higher values of H’ show highly diverse ecosystem while low values

show the contrary. Háněl (1995) found H’ in crop fields to vary between 2.66-

2.83. In present work, the value of H’ was higher in crop field as compared to

wastelands. This is in perfect agreement to earlier records where crop fields are

found to be highly diverse in comparison to other ecosystems (Ferris et al., 2001,

Tomar et al., 2006). Nitrogenous fertilizers increases or decreases nematode

abundance, as a consequence of the biomass production of plant root systems or

increase in microbial activity (Berger et al., 1986; Sohlenius & Boström, 1986;

Sohlenius, 1990). Nematodes in crop field had higher generic and individual

156  

abundance as compared to the nematodes in wasteland which is evident from the

study of Shannon’s diversity index. The lower H′ values for wasteland which

contrasts with the idea of Kandji et al. (2001) in all likelihood was because of

lack of diversity in the food resources particularly of the herbivores.

The maturity index (MI) provides useful information on the direction of

change within a particular habit. MI values for soil subjected to varying levels of

disturbances range from less than 2.0 in nutrient enriched disturbed systems to

±4.0 in undisturbed, pristine environments (Bongers & Ferris, 1999). Agricultural

practices, such as incorporating organic material (manure) into the soil stimulate

microbial activity and provide resources for opportunistic nematode species,

consequently, there is a rapid decrease in the MI followed by a gradual increase

during subsequent succession (Bongers & Ferris, 1999). In the present study MI

ranges from 2.1-2.59 in crop field and 2.36-3.66 in wasteland and is consistent

with earlier observations (Háněl, 1994, 1998; Bongers, 2001; Tomar & Ahmad,

2009, Dechang et al., 2009). Higher MI values for wasteland could be expected as

in undisturbed soil the ratio of higher functional guild species (dorylaims) to low

functional guild species (rhabditidae, panagrolaimidae etc.) is much greater than

in the crop field (27.2 - 31.8 vs 11.7 - 42.5). The highest value of MI in the crop

field was observed in April, several weeks after harvesting. One key factor that

may be responsible is the rapid decline of bacteriovores and fungivores

accompanied by little or no change in the omnivore and predator populations. The

MI values for wasteland indicate it to be a more stable habitat, presumably

because it is free from human intervention and with limited grazing. Here also the

maximum MI value of 3.66 is most probably brought about by a decline in the

157  

bacteriovore and fungivore population rather than in increase in the omnivore –

predator population.

The PPI is very good indicator of plant parasitic nematode resources. Pate

et al. (2000) estimated PPI values for crop fields at 2.3 while Neher & Campbell

(1994) recorded PPI as 2.82 and 2.51 in soybean plantations. The PPI values for

present study in crop field agree with earlier records. The lower PPI values for

wasteland is probably because of limited food resource and a lack of its variety.

The vegetation and the nematode population may have attained a state of

equilibrium as can be expected in undisturbed areas. On the other hand, cropping

provides varied and alternate sources of food to the plant parasites. PPI/MI is also

very good indicator of enrichment (Bonger’s et al., 1997). In present work low

PPI/MI values for wasteland and high values for crop field indicates that more

mature soil are less enriched as compared to manipulated soils. This is also borne

out by the greater EI in cultivated soil as compared to the undisturbed wasteland.

Similar observations have also been made by Háněl (2004) and Tomar & Ahmad

(2009). The Nematode Channel Ratio (NCR) indicates a dominance of bacterial

decomposition in both habitats but to varying degrees. Bacterial decomposition in

the wasteland is of smaller order as compared to the crop field. However this

contrasts with the observations of Bardgett and McAlister (1999) who argued that

fungal pathways of decomposition dominate in natural ecosystem.

Food web indices like EI, SI, and BI may provide an excellent means for

studying the stability of ecosystem, whether it is stressed, enriched or structured.

And provide information on the dynamics of the soil food web (Ferris et al.,

2001). Nematodes and other soil biota play an important role in releasing

158  

nutrients from bacterial biomass for the uptake by the plant roots. These

nematodes that respond first are enrichment opportunist and their biomass uptake

continues as long as the bacterial activity is high (Bongers & Bongers, 1998).

The values for SI in crop field during present study were lower as

compared to wastelands. The increase followed by a somewhat constant SI

probably indicates a structured soil in a state of equilibrium where nematode

populations fluctuate depending on the biotic and abiotic factors but not

significantly affecting one another. It has been reported in earlier studies that

generally in fallow soil and woodland the values of SI are higher which may due

to high abundance of omnivores and predators suggesting a food web with more

trophic linkages (Ferris & Matute, 2003). The higher the values of SI the more

complex is the community structure. Fallow lands and forests have been reported

to be more complex communities with reference to nematode in many studies

(Tomar & Ahmad, 2009). The values of SI for crop field fluctuated more

erratically and seemed to be governed more by the population of omnivores,

predators and possibly herbivores than by bacteriovores and fungivores. EI values

were higher for crop field and lower in wastelands. The values for EI were lowest

in October and highest being during September in wasteland, while for crop field

the highest value of EI was recorded during October while the lowest value was

observed at December, which incidently is the reverse for wasteland. Low values

of EI reflect low abundance of Rhabditidae and high abundance of Cephalobidae,

which can be well explained as the population of cephalobids is high compared to

rhabditids in October for wasteland and December for crop field. EI is generally

known to reflect availability of resources to the soil food web and response of

159  

primary decomposers to the resources (Ferris et al., 2004). The basal index (BI)

which is also a measure of enrichment show no significant changes over the

sampling time, except for the month of December in crop field and June in

wastelands.

Both in crop field and wasteland population of dorylaims show positive

correlation with MI and SI (P<0.01). As dorylaims have cp values in range of 4-5

and their abundance plays major role in higher values of these indices. The

incorporation of higher functional guilds for calculation of these indices results in

high degree of positive correlation. BI shows a high degree of negative correlation

(P<0.01) with dorylaims in both crop field and wasteland. This clearly indicates

the inverse relationship between dorylaimid and lower c-p value nematode guilds.

Cephalobids also show negative correlation with MI in wasteland (P<0.01) and

crop field (NS). An unusual fact of almost no correlation between PPI and

Tylechids in both areas is perplexing and is strikingly different from the

significant correlation reported by Háněl (1998) and Tomar & Ahmad (2009).

It may be concluded that nematode faunal analysis provides a good tool

for diagnosis of the complexity and status of soil food webs (Ritz and Trudgill,

1999). The presence and abundance of specific taxa is an indicator of the

complexity of the food web. Since related taxa, with similar morphological,

anatomical and physiological attributed, have similar feeding habits, useful faunal

analyses can be obtained by identification (Bongers & Ferris, 1999). As reported

earlier the present study also confirms that nematodes are very good indicators of

soil conditions. Although some contradictions have been found mainly the

absence of correlation between PPI and tylenchids is highly surprising as most

160  

studies in other parts of worlds as listed earlier, show significant correlation

between these parameters. Decomposition pathways were predominantly bacterial

in both the cropfield as well as wasteland, while crop field observations confirm

to the studies of earlier workers, the wasteland observation is in contrast to this.

These contradictions are difficult to explain as various abiotic factors have not

been taken into account, which can be a matter for further studies. Some factors

like anthropogenic activities resulting in the loss of top soil, can have profound

effect on the structure of the soil food web, which may severely limit its capacity

to support optimal nutrient cycling, plant growth and other enriched functions. It

is important to understand that indices developed from nematode faunal analysis

are based on proportions of the fauna in various functional guilds. They provide

an indication of the relative proportions of services and functions, but not of their

magnitude. The biomass and abundance of organisms in various functional guilds

is important in determining the magnitude of services. If biomass is also taken

into account we can have better understanding of the resources available to soil

food web organisms. The use of food web indices give better understanding of

wastelands where human intervention and other activities are very limited

throughout the year, but in case of crop field many factors play role in defining

the condition of soil and population dynamics of nematodes, therefore a

generalized study is not possible for food webs of crop fields.

 

 

 

 

161  

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