Singhaplax ockelmanni
Creators: name: Padate, Vinay P.
name: Cubelio, Sherine Sonia
name: Takeda, Masatsune
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Goneplacidae
Singhaplax
Singhaplax ockelmanni

description: Singhaplax ockelmanni (Serène, 1971)
(Figs. 2A, 3A–J, 10A–C)
Goneplax ockelmanni Serène, 1971: 915, 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 — Serène & Soh 1976: 18, fig. 15, pl. 6, fig. A.— Castro 2007: 713 (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.
Description. Carapace trapezoidal, 1.8–1.9 times as wide as long, glabrous, convex longitudinally, regions ill-defined (Figs. 2A, 3A); 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). Basal antennular article narrow, partially filling antennular fossa (Fig. 3B); basal antennal article short, squat, distalmost article not reaching frontal margin, flagellum lodged in orbital hiatus (Fig. 3B); epistome with anterior margin rounded, posterior margin slightly elevated; buccal cavity subquadrangular; mxp3 merus subquadrate, shorter and wider than ischium (Fig. 3C).
Chelipeds subequal in size in both sexes, 3.0 and 2.0 times CL in male and female, respectively, glabrous (Fig. 3D, E); 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).
Male pleon moderately wide; telson bluntly triangular, 0.7 times as long as wide (Fig. 3H). G1 beak-like, distal portion armed with row of spirally arranged spines (Fig. 10A, B). G2 longer than G1 (Fig. 10C).
Female pleon rounded; telson semi-circular, 0.2 times as long as wide, truncated distally (Fig. 3I); vulva of female moderately large, ovate, margins elevated by sternal prominence, vulvar cover absent (Fig. 3J).
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).
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) (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.
description: Published as part of Padate, Vinay P., Cubelio, Sherine Sonia & Takeda, Masatsune, 2024, First records of some coral reef-associated brachyuran crabs from the Nicobar archipelago, India, pp. 476-498 in Zootaxa 5486 (4) on pages 478-481, DOI: 10.11646/zootaxa.5486.4.2, http://zenodo.org/record/13210270