Jonas kalpakkamensis, Barathkumar & Das & Satpathy, 2016

Barathkumar, S., Das, N. P. I. & Satpathy, K. K., 2016, A new species of sand crab Jonas Hombron & Jacquinot, 1846 (Crustacea: Decapoda: Brachyura: Corystidae) from the southeastern coast of India, Zootaxa 4079 (4) : -

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 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.

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.

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 ).

Figures

FIGURE 2. Jonas kalpakkamensis n. sp., holotype male (29.0 × 16.0 mm) (ZSI / MBRC / D 1.244), 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.

FIGURE 3. Jonas kalpakkamensis n. sp., holotype male (29.0 × 16.0 mm) (ZSI / MBRC / D 1.244), G 1. A, left G 1 (ventral view); B, left G 1 (dorSal view); C, tip of the G 1 with SpineS (ventral view); D, right G 2; E, G 2 (tip). Scale barS: A, B = 1.0 mm, C = 0.1 mm, D = 0.5 mm, E = 0.2 mm.

FIGURE 4. A – I, Jonas kalpakkamensis n. sp., holotype (29.0 × 16.0 mm) (ZSI / MBRC / D 1.244), J, J. formosae (after Ng et al. 2000: fig. 8 b); K, J. formosae (after Ng et al. 2000: fig. 8 f). 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 G 1 (diStal part, view); G, G 1 diStal part (ventral view); H, G 1 (dorSal view); I, right G 2 (tip); J, right G 1; K, left G 2 (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.