Singhaplax ockelmanni ( Serène, 1971 )

Padate, Vinay P., Cubelio, Sherine Sonia & Takeda, Masatsune, 2024, First records of some coral reef-associated brachyuran crabs from the Nicobar archipelago, India, Zootaxa 5486 (4), pp. 476-498 : 478-481

publication ID	https://doi.org/ 10.11646/zootaxa.5486.4.2
publication LSID	lsid:zoobank.org:pub:29F6FDC3-3166-4309-A7B2-1582358AA1FD
DOI	https://doi.org/10.5281/zenodo.13210719
persistent identifier	https://treatment.plazi.org/id/03EA8791-7F29-FF8D-FF79-FA2AB194D4A4
treatment provided by	Plazi
scientific name	Singhaplax ockelmanni ( Serène, 1971 )
status

Treatment

Singhaplax ockelmanni ( Serène, 1971) View in CoL

( Figs. 2A View FIGURE 2 , 3A–J View FIGURE 3 , 10A–C View FIGURE 10 )

Goneplax ockelmanni Serène, 1971: 915 View in CoL , pl. 4, fig. D (type locality: Andaman Sea, Thailand).— Serène & Umali 1972: 78 (identification key), 82, figs. 82–89.— Davie et al. 2002: 331.— Ng & Davie 2002: 377.

Singhaplax ockelmanni View in CoL — Serène & Soh 1976: 18, fig. 15, pl. 6, fig. A.— Castro 2007: 713 View Cited Treatment (identification key), 713.— Ng et al. 2008: 80 (list).

Material examined. 1 male (4.8 × 2.5 mm) (IO/SS/BRC/00360), 1 female (4.6 × 2.5 mm) (IO/SS/BRC/00361), FORVSS stn. 38811, west of Tillangchong Island , Nicobars, India, 8.44°N, 93.59°E, 69 m depth, chain bag dredge, coll. V.P. Padate, 13 August 2019 GoogleMaps .

Description. Carapace trapezoidal, 1.8–1.9 times as wide as long, glabrous, convex longitudinally, regions ill-defined ( Figs. 2A View FIGURE 2 , 3A View FIGURE 3 ); frontal margin 0.25 times as wide as CW, nearly straight, gently deflexed ventrally; supraorbital margins wide (0.4 times CW) distinctly sinuous; orbital angle with acuminate, obliquely directed tooth; lateral margins distinctly converging behind lateral teeth; posterior margin gently sinuous.

Ocular peduncles as long as frontal margin, cornea slightly extending beyond cornea ( Fig. 3A, B View FIGURE 3 ). Basal antennular article narrow, partially filling antennular fossa ( Fig. 3B View FIGURE 3 ); basal antennal article short, squat, distalmost article not reaching frontal margin, flagellum lodged in orbital hiatus ( Fig. 3B View FIGURE 3 ); epistome with anterior margin rounded, posterior margin slightly elevated; buccal cavity subquadrangular; mxp3 merus subquadrate, shorter and wider than ischium ( Fig. 3C View FIGURE 3 ).

Chelipeds subequal in size in both sexes, 3.0 and 2.0 times CL in male and female, respectively, glabrous ( Fig. 3D, E View FIGURE 3 ); meri depressed, anterior margins dentate, posterior margins unarmed; carpi unarmed; propodi subcylindrical, slightly inflated in male; fingers curved, 0.5 and 0.8 times palm length in male and female, respectively; male dactylus distinctly curved, leaving a distinct gap, female dactylus gently curved, occlusal margins bluntly denticulate, fingers meeting at tips. Pereopods 2–5 shorter than chelipeds, compressed, meri, carpi, propodi and dactyli with thin long setae on dorsal and ventral margins, dactyli slightly shorter than propodi ( Fig. 3F, G View FIGURE 3 ).

Male pleon moderately wide; telson bluntly triangular, 0.7 times as long as wide ( Fig. 3H View FIGURE 3 ). G1 beak-like, distal portion armed with row of spirally arranged spines ( Fig. 10A, B View FIGURE 10 ). G2 longer than G1 ( Fig. 10C View FIGURE 10 ).

Female pleon rounded; telson semi-circular, 0.2 times as long as wide, truncated distally ( Fig. 3I View FIGURE 3 ); vulva of female moderately large, ovate, margins elevated by sternal prominence, vulvar cover absent ( Fig. 3J View FIGURE 3 ).

Colouration. Fresh specimen: Carapace, chelipeds and pereopods off-white; carapace with dark blotch on gastric region, small light brown blotches anteriorly on branchial regions; cheliped palm and fingers with 1 or 2 transverse brown bands ( Fig. 2A View FIGURE 2 ).

Biology. The present specimens were collected along with gorgonians and sponges from 69 m depth. Known to occur on muddy sand substrates down to depths of 80–87 m ( Castro 2007).

Remarks. Goneplax ockelmanni was described from a male from the Andaman Sea off the Thailand coast ( Serène 1971). Serène & Soh (1976) transferred this species to a new genus, Singhaplax , owing to the difference in the structure of antennules and G1 including species of Goneplax s.l., especially G. sinuatifrons Miers, 1886 . Singhaplax ockelmanni shares a G1 morphology of a bilobed apical process with S. dichotoma Castro, 2007 and S. lipkei Naruse & Castro, 2010 . However, it differs from the latter two species in the beak-like apical processes of the G1 ( Fig. 10A, B View FIGURE 10 ) (versus G1 with broad, triangular apical processes in S. dichotoma ( Castro 2007: fig. 35B); thick, spinous apical processes in S. lipkei ( Naruse & Castro 2010: fig. 3a, b)). The morphology of the Indian specimens conforms to the photograph of the holotype specimen provided by Serène (1971: pl. IV fig. D) and the line illustrations of the carapace, chelipeds, male pleon and gonopods provided by Serène & Umali (1972: figs. 82–89).

Geographical distribution. Andaman Sea coast of Thailand ( Serène 1971), the Philippines ( Castro 2007), and off Nicobars, India (present study). The present observation is the first record from Indian waters.

Kingdom	Animalia
Phylum	Arthropoda
Class	Malacostraca
Order	Decapoda
Family	Goneplacidae
Genus	Singhaplax