a new species of sand crab jonas hombron \u0026 jacquinot, 1846 (crustacea: decapoda: brachyura:...

$: A new species of sand crab Jonas Hombron \u0026 Jacquinot, 1846 (Crustacea: Decapoda: Brachyura: Corystidae) from the southeastern coast of India$
ZOOTAXA

ISSN 1175-5326 (print edition)

ISSN 1175-5334 (online edition)Copyright © 2016 Magnolia Press

Zootaxa 4079 (4): 480–486

http://www.mapress.com/j/zt/Article

http://doi.org/10.11646/zootaxa.4079.4.7

http://zoobank.org/urn:lsid:zoobank.org:pub:874128E6-42FD-4F10-B4A6-E8F7B115924F

A new species of sand crab Jonas Hombron & Jacquinot, 1846 (Crustacea:

Decapoda: Brachyura: Corystidae) from the southeastern coast of India

S. BARATHKUMAR1, N. P. I. DAS1 & K. K. SATPATHY1,2

1Environmental and Safety Division, Radiological Safety & Environmental Group, Reactor Engineering Group, Indira Gandhi Centre

for Atomic Research, Kalpakkam, Tamil Nadu, India2Corresponding author. E-mail: [email protected]

Abstract

A new species of sand crab of the genus Jonas Hombron & Jacquinot, 1846 (family Corystidae) is described from speci-

mens collected from Kalpakkam, southeastern coast of India. Two other species, J. indicus (Chopra, 1935), and J. choprai

Serène, 1971, have previously been recorded from this area. A detailed description of the new species is given and com-

pared with the closely related J. formosae Balss, 1922, also from the Indo-West Pacific.

Key words: edible crustaceans, sand crabs

Introduction

Among the edible marine crustaceans, brachyuran crabs constitute a third of the commercial value of Indian

seafood (Varadharajan & Soundarapandian 2012). In terms of species diversity, however, brachyuran crabs have

the most taxa, with 6559 known species (Ng et al. 2008), 990 of which are known from Indian waters (Kathirvel

2008). The number of species reported from the Tamil Nadu coast, southern India, are 404 (Kathirvel 2008), of

which, 103 species are known along Chennai (Krishnamoorthy 2007, 2009; Pillai & Thirumilu 2008). The family

Corystidae is regarded as one of the oldest brachyuran families and can be traced back to the Jurassic Period

(Guinot et al. 2007), and is characterized by the presence of a long respiratory tube formed by modified antennae

(Davie 2002). Because of their small size and infrequent catch in trawls, these crabs have little commercial value.

They are often known as masked crabs or sand crabs because of their dorsal appearance and habitats, respectively.

These are often found buried completely in the sand and are rarely caught. Two species belonging to the family

Corystidae have so far been reported from Indian waters, namely, Jonas indicus (Chopra, 1935) (described as a

Gomeza) from the mouth of Hooghly River and later from Chennai coast (Pillai & Thirumilu 2008), and Jonas

choprai Serène, 1971, from the Parangipettai coast, south of Chennai (Manokaran et al. 2008). The present

communication deals with the description of a new species of Jonas based on specimens obtained from off

Kalpakkam, 50 km south of Chennai.

Material and methods

On three occasions, 4 males were collected from the catches landed at Sadras, a fishing village close to Indira

Gandhi Centre for Atomic Research (IGCAR), Kalpakkam (Fig. 1) by bottom-set gill nets set at a depth of 20–30

m. Measurements (carapace length × width) were made to the nearest 0.1 mm by a caliper and spines were counted

using a stereomicroscope. The carapace length was measured from the tip of the rostrum to the posterior carapace

margin. The carapace width measurement includes the spines. Before preserving in 10% formaldehyde, specimens

were photographed to record the colour pattern, using a Sony Mavica MVC-CD500. For the first and second

gonopods, the abbreviations G1 and G2 are used, respectively.

480 Accepted by P. Castro: 15 Dec. 2015; published: 15 Feb. 2016

FIGURE 1. Distribution of Jonas species.

Systematics

Superfamily Corystoidea Samouelle, 1819

Family Corystidae Samouelle, 1819

Genus Jonas Hombron & Jacquinot, 1846

Jonas kalpakkamensis n. sp.

Figs. 2–4A–I

Holotype. Male (29.0 × 16.0 mm) (Marine Biology Regional Collection Center, Zoological Survey of India,

Chennai (ZSI/MBRC/D1.244), Kalpakkam coast, Tamil Nadu, India, from tangle nets, collected by S.

Barathkumar, 10 July 2013.

Paratypes. 1 male (24.0 × 13.0 mm) (Crustacean collection of Environment and Safety Division (EnSD),

Indira Gandhi Centre for Atomic Research (IGCAR), EnSD/2013/34), locality same as holotype, coll. S.

Barathkumar, 25 February 2014; 2 males (22.0 × 11.0 mm; 32.0 × 16.0 mm) (EnSD/2013/35-36), locality same as

holotype, from tangle nets, collected by S. Barathkumar, 7 July 2014.

Diagnosis. Carapace longitudinally ovate; dorsal surface with grooves between regions; most elevated areas

with clusters of pearliform granules; front with a bifid rostrum; supraorbital spine longer than rostrum; orbital spine

larger than first anterolateral spine; size of anterolateral spines decreasing from first to ninth; tenth larger than

ninth, situated at posterolateral corner, pointing obliquely backwards; arm, palm of chelipeds covered by setae;

borders of ambulatory legs densely setose; ventrobasal region of merus of fourth ambulatory leg with 3 spines; G1

Zootaxa 4079 (4) © 2016 Magnolia Press · 481A NEW JONAS

hooked with elongated filamentous distal part; shaft of elongated part with row of small posteriorly directed spines

from distal tip to middle.

Description. Entire surface covered with small setae, granules; carapace longitudinally ovate (Fig. 2A);

supraorbital spine slightly longer than bifid rostrum; orbital spine longer than first anterolateral tooth (Figs. 2C, D);

pearliform granules arranged in clusters on elevated frontal, gastric, cardiac, intestinal regions; granules arranged

longitudinally on branchial region; distinctive grooves between gastric, cardiac, branchial regions; stalked eyes

large filling orbits; anterolateral margin of carapace convex with 10 teeth on each side, first one largest; size of

anterolateral teeth decreasing from first to ninth; tenth larger than ninth, at posterolateral junction, pointing

obliquely backwards; antennal flagellum almost equal to carapace length, strongly setose; third maxillipeds

elongated with granular surface (Fig. 4C); merus quadrate, half length of ischium; inner border of exopod lined

with tubercles, with long flagellum.

FIGURE 2. Jonas kalpakkamensis n. sp., holotype male (29.0 × 16.0 mm) (ZSI/MBRC/D1.244), A, carapace, dorsal view; B,

ventral view; C, frontal region (dorsal view); D, frontal region (lateral view); E, right of fourth ambulatory leg with 3 spines; F,

abdomen, dorsal view (setae denuded). Scale bars: A, B = 10.0 mm, C = 3.0 mm, D= 0.2 mm, E, F = 0.1 mm.

BARATHKUMAR ET AL. 482 · Zootaxa 4079 (4) © 2016 Magnolia Press

FIGURE 3. Jonas kalpakkamensis n. sp., holotype male (29.0 × 16.0 mm) (ZSI/MBRC/D1.244), G1. A, left G1 (ventral

view); B, left G1 (dorsal view); C, tip of the G1 with spines (ventral view); D, right G2; E, G2 (tip). Scale bars: A, B = 1.0 mm,

C = 0.1 mm, D = 0.5 mm, E = 0.2 mm.

Chelipeds equal in size, covered with granules, long setae; single spine on distal part of inner, outer margins of

merus; inner carpal spine long, sharp, followed by small spine behind it, prominent large basal tubercle; outer

margin of carpus with 2 sharp spines; upper dorsal ridge behind movable finger with 3, 4 sharp spines; mid-part of

outer surface of palm with 2, 3 spines; rounded teeth on cutting margins of dactylus, pollex; finger tips curved.

Ambulatory legs relatively long, fringed with setae; second, third leg almost equal; ischium of last ambulatory

leg without spine, as in other legs; 3 spines present at base of merus of last ambulatory leg, single spine in dorsal

view, 2 other spines on ventral view; all 3 spines inwardly curved (Figs. 2E, 4D); shape of dactylus of last

ambulatory leg spatuliform.

Abdomen short, first 3 somites not wide, fourth, fifth somites very wide, sixth somite half width of fifth

somite, telson triangular with rounded tip, stiff setae; fourth somite triangular; fifth somite with 3 projections, 2

large ovate ones on marginal side, subovate one on upper border, separated by deep groove; abdomen covered with

dense setae; sixth somite with 4 projections, one on each lateral side, third one on upper border, fourth one on lower

border (Figs. 2F, 4E).

G1 L-shaped in ventral view, with stout basal, slender, long distal shaft; tip of elongated distal shaft

filamentous (Figs. 3A, 4F); below filamentous tip, row of small posteriorly directed spines on outer margin,

increasing in size from distal (Figs. 3C, 4G); G2 short, with broad base; bent basally, then directed straight up, apex

portion spoon-shaped (Figs. 3E, 4I).

Coloration. In freshly preserved specimens, the carapace is reddish with the elevated parts orange-red and the


larger granules whitish; grooves in lighter colour; ambulatory legs with orange patches, setae bordering legs

reddish.

Etymology. The species name is derived from the name of the type locality.

Habitat. Jonas kalpakkamensis n. sp. was found on sandy mud in shallow (20–30 m) coastal waters off

Kalpakkam.

FIGURE 4. A–I, Jonas kalpakkamensis n. sp., holotype (29.0 × 16.0 mm) (ZSI/MBRC/D1.244), J, J. formosae (after Ng et al.

2000: fig.8b); K, J. formosae (after Ng et al. 2000: fig.8f). A, frontal region (dorsal view); B, frontal region (lateral view); C,

left third maxilliped; D, merus of right fourth ambulatory leg (setae denuded); E, abdomen (setae denuded); F, right G1 (distal

part, view); G, G1distal part (ventral view); H, G1(dorsal view); I, right G2 (tip); J, right G1; K, left G2 (distal part). Scale bars:

A, B, D = 5.0 mm, C = 3.0 mm, E = 0.2 mm, F, H = 1.0 mm, G = 0.1 mm, I = 0.3 mm.

Remarks. The other Jonas species currently known from India are J. choprai and J. indicus (Manokaran et al.

2008; Pillai & Thirumilu 2008). In general morphology, J. kalpakkamensis n. sp. most closely resembles J.

formosae, a species from the East and Southeast Asia re-described and figured by Ng et al. (2000). Compared to J.

formosae, J .kalpakkamensis n. sp. has relatively more pearliform granules on the elevated regions (Fig. 4A) (cf.

Ng et al. 2000: fig. 6b), more like the condition in J. distinctus from East Asia (cf. Ng et al. 2000: fig. 6a). There

are also three spines at the ventrobasal margin of the merus of the last ambulatory leg in J. kalpakkamensis n. sp.

(Figs. 2E, 4D), whereas there is only one in J. formosae, (cf. Ng et al.2000: fig. 8g). While the G1 structures of the

two species are superficially similar, the distal elongated part of G1 of J. kalpakkamensis n. sp. is not as strongly

curved (Figs. 3A, B; 4F, H) compared to J. formosae (Fig. 4J) (cf. Ng et al. 2000: fig. 8b). The basal part of the G2


is also gently curved in J. kalpakkamensis n. sp. (Figs. 3D, E; 4I), whereas that in J. formosae the basal part has an

acute projection (Fig. 4K) (cf. Ng et al. 2000: fig. 8f).

Ng et al. (2008) reported J. formosae from Phuket, western Thailand. Considering that this location is in the

Indian Ocean, these records should also be re-examined to see if they prove to belong to J. kalpakkamensis n. sp.

instead. Jonas kalpakkamensis n. sp. is quite different from J. choprai, which was reported from Parangipettai

coast by Manokaran et al. (2008), some 120 km south of the current locality. Jonas choprai differs from J.

kalpakkamensis n. sp. in having a relatively broader carapace and longer supraorbital spines (Fig. 2C) (cf. Serène

1971: pl. 1 figs. C, D). The dorsal carapace granulation on J. kalpakkamensis n. sp. are of different sizes, whereas

in J. choprai, these granules are more uniform (Figs. 2A, 4A) (cf. Serène 1971: pl. 1 fig. C). The supraorbital spine

in J. choprai is also more prominent and much longer than the rostrum and frontal process. Moreover, the first

anterolateral spine of J. choprai is stronger and longer than the rest, whereas the structures are more similar in form

in J. kalpakkamensis n. sp. (Fig. 2C, D) (Serène 1971: pl. 1 figs. C, D). In J. kalpakkamensis n. sp. the basal

antennal segment is sparsely granular, whereas it is strongly granular with sharp tubercles in J. choprai (Serène

1971: pl. 1 fig. C). The basis-ischium of the last ambulatory leg lacks spines in J. kalpakkamensis n. sp. (Fig. 4D),

whereas the leg of J. choprai has a distinct ventral spine (cf. Ng et al. 2000: fig. 10a).

The other reported species from Indian waters is Jonas indicus (Chopra, 1935). The species was described

from near the mouth of Hoogly River in West Bengal, India, on the basis of a small specimen (Chopra 1935). The

species has been recently reported from Chennai coast (Pillai & Thirumilu 2008), which was only the second report

of the species after its description. Ng et al. (2000) questioned the validity and status of J. indicus. It was originally

described as a subspecies of Gomeza distinct and whether it was a juvenile of Jonas or Gomeza. Ng et al. (2008),

however, listed it as a valid species of Jonas. From the original description of the species by Chopra (1935: pl. 9

figs. 4, 5), the species has minute granulation along with larger tubercles dorsally, a condition that is superficially

similar to that of J. kalpakkamensis n. sp. The carapace regions of J. indicus, however, are more prominently

developed (cf. Chopra 1935: pl. 10 fig. 4), which clearly distinguishes it from J. kalpakkamensis n. sp. (Fig. 2A).

The prominent curved lateral spines, comparatively more ovoid shape of the carapace and relatively larger

posterolateral teeth of J. indicus are features more similar to Gomeza species (cf. Chopra 1935: pl. 9 figs. 4,5) and

very different from those observed in J. kalpakkamensis n. sp. (Fig. 2C, D). Similarly, the abdomen of J. indicus

(cf. Chopra 1935: fig. 15c) is proportionately narrower than that of J. kalpakkamensis n. sp. (Figs. 2F, 4E). It is

worth noting that Persian Gulf records of “Gomeza distincta” and “Jonas distinctus” by MacGilchrist (1905) and

Stephensen (1946) may well be J. indicus instead.

Jonas distinctus s. str. is currently regarded as a strictly western Pacific taxon (Ng et al. 2000) and is easily

recognised by its distinctive short, stout G1 (cf. Ng et al. 2000: fig. 7a). The identities of two Jonas species is less

clear. Jonas macrophthalmus Jacquinot 1853, the type species, was described from a single female specimen from

near New Guinea (Jacquinot 1853: 88, pl. 8 fig. 4). On the basis of the original description and figures, it differs

clearly from J. kalpakkamensis n. sp. in the absence of spines on the merus of last ambulatory leg. Jonas leuteanus

Ward, 1933, was described from Lindeman Island in Queensland, Australia by but from his description and figures,

this species differs from J. kalpakkamensis n. sp. in not having any spine on the merus of the last ambulatory leg,

and the dorsal carapace surface is uniformly covered with fine spinules with pearliform granules on the elevated

regions in J. kalpakkamensis n. sp. (Fig. 4A).

Acknowledgements

The authors express their sincere gratitude to Peter K.L. Ng, National University of Singapore, for his valuable

suggestions for improving the manuscript. The authors gratefully acknowledge M. Selvanayagam, Loyola Institute

of Frontier Energy, India, for his support and valuable suggestions during the study. We are also express sincere

gratitude to Dr. M. K. Dev Roy, Former Scientist, Zoological Survey of India and Dr. M. Kathirvel, Former

Principal Scientist, Central Institute of Brackishwater Aquaculture, for their help in the taxonomy and valuable

suggestions in studying the specimens.


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a new species of sand crab jonas hombron \u0026 jacquinot, 1846 (crustacea: decapoda: brachyura:...

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