Alcolyra alcocki ( Kemp, 1915 ), 2022

Trivedi, Jigneshkumar N., Mitra, Santanu & Ng, Peter K. L., 2022, Alcolyra, a new genus of leucosiid crab (Crustacea: Decapoda: Brachyura) from India, Zootaxa 5091 (2), pp. 383-392 : 390-392

Alcolyra alcocki ( Kemp, 1915) n. comb.

( Figs. 1–5)

Philyra alcocki Kemp 1915: 212 , pl. 12 fig. 2, text figure 2, 3; Takeda & Nakasone 1991:23 (in discussion); Deb 1995: 349; Mohapatra et al. 2007: 247 (in list); Dev Roy & Nandi 2008: 498 (in list); Ng et al. 2008: 93 (in list); Sahoo et al. 2008: 178 (in list); Galil 2009: 281 (in list); Mahapatro et al. 2015: 9 (in list); Dev Roy 2017: 209 (in list): Dev Roy & Rath 2017: 93 (in list); Trivedi et al. 2018: 49 (in list): Ng 2021: 370 (in discussion)

Material examined. Types: Lectotype (herein selected), male (CL 12.5 mm; CW 11.9 mm) ( ZSI. C8944 /10), sandy or muddy bottom, 1.5 to 3 m, Chilika Lake , Odisha state, India, coll. S. Kemp. Paralectotype, female (CL 13.3 mm; CW 11.6 mm)( ZSI. C8944 /10), same data as lectotype .

Others: 2 males (CL 12.7 mm; 12.1 CW mm; 12.4 CL mm;11.7 CW mm) ( ZSI. C7734 /2), sandy bottom, 1.5 to 2 m, Kapuda Ghat, Chilika Lake , Odisha state, India, 4 February, 2016, coll. S. Mitra ; 1 male (CL 12.0 mm; CW 11.0 mm), 1 female (CL 15.3 mm; CW 13.7 mm) ( LFSC. ZRC- 69), muddy bottom, 1.5 to 2 m, Chilika Lake , Odisha state, India, 1 March, 2020, coll. K. Patel.

Description. Males: Carapace suborbicular, slightly longer than broad. Dorsal surface convex,covered with punctae, regions relatively distinct; cardiac, branchial, intestinal regions elevated, median ridge relatively faint, extending from frontal region and merging with elevated intestinal region; protogastric region depressed, less punctate ( Figs. 1A, B, 2A, B); cardio-gastric region separated from branchial region on both sides by shallow depression; intestinal and cardiac regions with patch of tubercles, more strongly developed in males ( Figs.1A, B, 2A, B); branchial region with 2 tuberculated ridges originating from posterolateral margin, longitudinal anteriorly, oblique posteriorly, posterior branchial ridge merging anterior branchial ridge longitudinally ( Figs.1A, B, 2A, B); hepatic region excavated, forming broad shallow depression margins not merging anteriorly, extended till outer limit of orbit, posteriorly joins anterolateral margin at well-marked obtuse angle, floor of depression smooth with scattered punctae, lower margins of the depression finely beaded, strongly convex inferiorly ( Figs.1A, B, 2A, B). Anterolateral, posterolateral, posterior margins beaded; epibranchial angle obtuse; posterolateral margin sinuous, convex ( Figs.1A, B, 2A, B). Front anterior margin almost straight with single median tooth projecting beyond visible margin of epistome, small notch on margin of epistome beneath eye ( Figs.1A, B, 2A, B). Posterior margin concave in male, broadly triangular blunt teeth on lateral sides ( Figs.1A, B, 2A, B).

Third maxilliped surface with numerous punctae; merus 0.9 times as long as ischium along inner margin; ischium 1.8 times longer than wide ( Figs. 1C, 2C, 5B); propodus and dactylus not visible in external view when reposed, articulating on inner surface of merus, dactylus apex with long setae ( Figs. 1C, 2C, 5B). Exopod outer margin convex, much longer than wide, almost twice length of merus, outer and inner margins of ischium, merus and exopod with fringe of setae ( Figs. 1C, 2C, 5B).

Chelipeds equal, about 1.5 times length of carapace length, surface minutely granulated ( Figs. 1A, 2A). Merus cylindrical, symmetrical along length, surfaces minutely granulate. Carpus smooth, unarmed. Chela stout, surfaces smooth ( Figs. 1A, 2A); palm longer than broad, dorsoventrally compressed; fingers almost as long as palm, terminating in sharp tooth, outer margins with scattered setae, dactylus inner surface with single longitudinal groove, pollex with 2 longitudinal ridges on inner surface, cutting edges of fingers with blunt denticles with scattered setae ( Figs. 1A, 2A).

P2–P5 subcylindrical ( Figs. 1A, 2A); total lengths decreasing from first to last pair, merus and carpus glabrous, unarmed; merus longest as compared to carpus, propodus and dactylus, upper and lower margins of propodus and dactylus covered with setae ( Figs. 1A, F 2A, F).

Thoracic sternum transversely broad, surface punctate; sternites 1–3 completely fused without trace of sutures ( Figs. 1E, 2E, 4A, C); sternite 3 separated from sternite 4 by shallow groove; sternites 4–7 progressively narrow; outer lateral margin of sternite 4 swollen forming longitudinal ridge on either side in adults, sternite 5 with large tubercle near inner lateral margin on either side opposite to base of first ambulatory leg; sternite 8 visible when pleon closed, between margins of pleonal somites 2 and 3; penis arising under constriction between sternites 7 and 8 ( Figs. 1E, 2E, 4A, C). Sternopleonal cavity deep; reaching to mid distance between fused thoracic sternites 1–3 ( Figs. 1E, 2E, 4A, C).

Pleon narrow, long ( Figs. 4A, C, 5A); somite 1 longitudinally narrow, wide ( Figs. 4A, C, 5A); somite 2 yokelike, reaching coxae of fourth ambulatory leg ( Figs. 4A, C, 5A); somite 3–5 fused, forming elongated trapezoidal plate, shallow suture just visible between somite 3 and 4, surface sparsely punctate ( Figs. 4A, C, 5A); somite 6 longitudinally rectangular, free, surface unarmed, broad base with rounded posterolateral corners, posterior margin slightly concave medially ( Figs. 4A, C, 5A); telson nearly twice longer than broad, triangular, with curved apex ( Figs. 4A, C, 5A).

G1 long, slender, tip with short setae, apical process spatuliform ( Figs. 5C–F). G2 short, slender ( Fig. 5G)

Females: The female carapace is similar to that of males in appearance except for the straight posterior margin ( Figs. 3A, D) and the adult chelipeds are proportionately shorter ( Figs. 3A, D).The pleon is longitudinally ovate, with somites 1 and 2 free and somites 3–6 completely fused to form a domed plate that completely covers the thoracic sternum ( Fig. 3B, E). The telson is triangular and mobile ( Fig. 3B, E). The vulvae are large, obliquely ovate and positioned on the anterior part of sternite 6, without any sign of a sternal vulvar cover ( Fig. 3C, F).

Colour. The coloration of fresh specimen slightly varies from that given by Kemp (1915). The carapace is pale brown (pale French grey according to Kemp 1915) with irregular patches of purple red. The chelipeds are dark purple with fingers pale brown; the ambulatory legs are pale brown in colour, and the ventral surface of the cephalothorax is whitish.

Distribution. So far, the species is only known from its type locality Chilika Lake located in Odisha state of India ( Kemp 1915; Deb 1995; Mohapatra et al. 2007; Dev Roy and Nandi 2008; Sahoo et al. 2008; Mahapatro et al. 2015; Dev Roy 2017; Dev Roy and Rath 2017; Trivedi et al. 2018).

Ecology. The type and fresh specimens were collected from the depth ranging from 5 to 10 feet with muddy or sandy bottom in Chilika Lake located in Odisha state of India .

Remarks. Kemp (1915: 215) noted that he had a total of 16 specimens collected from various parts of Odisha state in India: Rambha to Barkul and Nalbano at Chilika Lake, and that “the type specimens are registered under no. 8944/10” ( Kemp 1915: 216). No holotype was identified. In the ZSI, there are two specimens catalogued under this number, a male and a female, and as such, both are here regarded as syntypes. The whereabouts of the other 14 specimens is not known, but they should not be regarded as syntypes as they were not identified as such in the original paper. For taxonomic stability, the male syntype is here designated the lectotype of P. alcocki Kemp, 1915 .

The fresh specimens obtained in the present study agree well with the description and figures of Kemp (1915). They differ only slightly from the types in terms of having faint two tuberculated ridges present on the branchial region which are more prominent in types. With regards to the male pleon, Kemp (1915: 214) commented that “The first segment is acutely produced on either side and, though it appears distinct, is in reality fused to the succeeding piece.” We have examined the lectotype male and we confirm that the two somites are actually mobile and not fused, as in the fresh material.