A predatory nematode eating another nematode

Stoma STRUCTURE IN PREDATORY NEMATODEs

By :-Aaliya TaiyabM.Sc. Final ZoologySem IVA.M.U

1

In soil most common groups of nematodes are :- Bacterial feeders, Fungal feeders, Plant parasites, Predators, and Omnivores. Predatory nematodes feed on protozoa and other soil nematodes. Since the predator

has to feed upon active prey, it must have a mechanism to grasp the active prey and then to cut or puncture its cuticle.

2

Soil inhabiting predaceous form are grouped into different feeding types:Type I: They feed by cutting the body of prey and then sucking its body contents as they are unable to engulf intact preys.Diplogasterid.

Type II: They feed by a combined action of cutting and sucking as well as at times engulfing the whole prey. Mononchida

Type III: They feed only by puncturing or piercing the cuticle of the prey and then sucking the body contents.Dorylaimida and Aphelenchida. (Seinura sp.)

Mononchus Dorylaimus Aquatides Actinolaimus Seinura Monchoides

3

STOMA: Basic Structure• Buccal cavity and buccal capsule make up the stomaDe Ley et al. (1995) – based on TEM :-1. Cheilostom 2. Gymnostom3. Stegostom

Cheilostom

Gymnostom prostegostommesostegostom

metastegostomtelostegostom

Stegostom

4

Movable and immovale stomal structures (armature)

Odontia and onchia Dentate and denticulate Fossoria or mandible Protrusible spear

odontia onchia

Mandibles Protrusible spearDentate and denticulate 5

6

Mononchida Walls-heavy sclerotisation –thick and very prominent Made up of two sets of three plates 1. anterior- vertical 2. posterior – oblique plates Each set – 3 plates (tripartite) 1. one dorsal – dorsal tooth. Non movable, vary in position, shape and

size. 2. two subventral walls – may or may not bear tooth, teeth or

denticles. When present these are known as subventral or submedian armature

7

On the basis of shapes Mononchoidea : barrel shaped with tapering base Anatonchoidea : with flat base Bathyodontoidea : long cylindrical, thin walled

Shape :- barrel shaped, globular, oval, rectangular or long cylindrical, thin walled.

A: MononchusB: ClarkusC:CoomansusD: MylonchulusE:SporonchulusF: CobbonchusG: PrionchulusH: AnatonchusI: IotonchusJ: MiconchusK: HadronchusL: MononchulusM; Oionchus

8

•Absent :- Mononchus, Coomansus, Iotonchulus

•Identical to dorsal tooth :- Miconchus, Or although similar in sizes, shape and position, pointing posteriad as in Anatonchus , or located slightly posterior as in Cobbonchus

•Subventral teeth are several & are arranged in single longitudinal row on each cell (eg. Actus) or a ‘rib like’ structure along the row of teeth as in Prionchulus

•Subventral teeth are numerous and are arranged in almost regular transverse rows as in Mylonchulus but are irregularly scattered in Sporonchulus

9

Rhabditida

Rhabditina Diplogasterina (predators)

10

Diplogasterina Cutting and Sucking type Cheilostomal plates/rugae help in grasping

the prey gymnostom Stegostom bear dorsal tooth which differ in

shape and sizes and seems to be the main killing weapon

It receives the duct from the dorsal pharyngeal gland, it ejects the secretions on the prey for extra- corporal digestion.

Examples:Diplogaster, Mesodiplogaster, Butlerius, Mononchoides, Fictor, Neodiplogaster, represents some of the predatory diplogasterids 11

12

13

Protrusible stylet which is responsible for penetrating/puncturing the prey cuticle/host plant.

Basic structure: o Vestibulumo Guiding apparatus axial spear or odontostyleo Stomal armatureo Muscles

Dilator muscles

Protracror muscles

Retractor muscles

Mural tooth

14

1. Axial Spear (Dorylaimina):- Odontostyle + odontophore Vestibulum more prominent Guiding ring better developed Odontostyle broader and centrally placed and

has a dorsal aperture odontophore formed by cuticularisation of the

anterior part of oesophastom, used for supporting & ejecting mechanism for the odontostyle

2. Mural tooth (Nygolaimina) Thin walled vestibulum Weakly developed guiding ring Well cuticularised double walled guiding sheath Lies posteriorly in the left ventrosublateral Narrow, without aperture and placed

asymmetrically

15

Aporcelaimidae Comprises exclusively of predatory forms Well developed widely seperated lips Hexagonal oral aperture Plicated guiding ring Wide odontostyle with wide aperture,Aporcelaimus : aperture occupying more then

one-half length

Qudsianematidae Odontostyle cylindrical, dorylamoid with wide

lumen and aperture. Guiding ring single or double. Odontophore rod like or with sclerotised basal flanges or knobs.

Labronema and labronemella : the lips are more developed for grasping the active prey and the odontostyle and odontophore are more strong

16

Discolaimus: lips are further widened and become disc like to form an arch over the oral aperture, odontophore very sharply pointed with an aperture about 50% of its length

Carcharolaimus, Carcharoides, Caribenema: strong basket like cheilostomal sclerotisation

17

Actinolaimidae

•Exclusively predatory forms

•Characterised by presence of four large tooth/onchia, teeth and denticles.

•Vestibule wide, vestibular ring –single or double forming a crown with large no. of prongs around oral aperture., adapted for grasping the active prey

•Onchia generally separated from each other (Actinolaimus sp., Neoactinolaimus sp.,) but sometime basally fused; ring like structure (Metactinolaimus)

metactinolaimus 18

Vestibular wall may be corrugated and provided with denticles (Paractinolaimus sp., westindicus sp.,)

•Onchia may be simple or provided with secondary tooth (Neoactinolaimus sp.,)

•Scleroactinolaimus punctatus: cheilostom in addition to onchia is provided with four strongly sclerotized plates

•Westindicus sp., : vestibule consist of numerous ribs forming a basket-like structure.

Paractinolaimus Westindicus

Neoactinolaimus

19

Tylenchida

Tylenchina

AphelenchinaPredatory : Seinura

20

Seinura and Laimaphlenchus Small narrow spear with a fine lumen but

without basal knobs Spear – piercing and sucking type

21

Exhibit diversity in terms of stomal armature Less explored in terms of feeding habit mostly marine .

Predatory enoplids grips its prey with the three eversible teeth and the cylindrical pharyngeal cavity acts as a sucking organ.

Largerly Stoma contains three mandibles

Oncholaimidae: feed on other nematodes

Large capsuliform, cheilostomal stoma

Onchomailus : left subventral tooth is largest

Thalassogenus: interesting marine oncholaimid

Oncholaimus 22

Ironidae ; mainly predatory forms – anterior feeding apparatus consist of three parts:

o Large part cheilostomal in origin that leads into oesophastom.

o Median part-double walled cylinder like : three equal teeth are present

o Proximal part of oesophastom : oblique radial muscles

Ironus: cheilostom triangular in shape

Ironus

Thalassironus

Trissonchulus

Thalassironus sp. –two dorsal tooth with apices pointing in different directions whereas in Trissonchulus sp., the two dorsal teeth are fused at base and the cheilostomal wall is denticulate

23

24

In the absence of prey, some nematodes can switch to omnivorous mode of feeding. Ex dorylaims

25