Visayax osteodictyon Mendoza & Ng, 2008

(Figs. 2F, 8A–F, 10P–R)

Visayax osteodictyon Mendoza & Ng 2008: 392, figs. 3, 4, 9B (type locality: Pamilacan Island, Bohol Sea, central Philippines, 15–22 m depth).— Bouchet et al. 2009: 14.— Mendoza & Ng 2010: 70, Table 1.— Lai et al. 2011: 441, Table 1.— Takeda & Komatsu 2018: 170, fig. 5F. — Maenosono 2021: 30 (remarks).

Material examined. 1 male (5.2 × 3.6 mm) (IO/SS/BRC/00194), FORVSS stn. 38818, south of Great Nicobar Island, Nicobars, India, 6.65°N, 93.83°E, 56 m depth, chain bag dredge, coll. V.P. Padate, 16 August 2019 .

Description. Carapace hexagonal, 1.4 times as wide as long, regions defined by reticulate pattern of fused granules (Figs. 2F, 8A); frontal margin deflexed, indistinctly bilobed, lobes separated by a shallow U-shaped notch; supraorbital margin short; anterolateral margin strongly arcuate, irregularly serrated, forming angular junction with concave posterolateral margin; posterior margin nearly straight (Fig. 8A).

Antennules folding transversely; basal antennal article large, subrectangular, distinctly granular, flagellum lodged in orbital hiatus (Fig. 8B); epistome short, posterior edge elevated, with median projection; buccal cavity subrectangular; mxp3 merus subquadrate, shorter than ischium with 2 depressions separated by an oblique granular ridge, antero-external angle rounded (Fig. 8C).

Chelipeds subequal, 1.5 times as long as CL, surfaces bearing reticulate pattern of fused granules similar to carapace; palm with granular dorsal and ventral margins; fingers slightly shorter than palm, bearing rows of granular ridges continuing from granular rows on palm (Fig. 8D–E). Pereopods 2–5 shorter than chelipeds, margins setose, meri with granular margins, dorsal surface of P5 and carpi of all pereopods with reticulate pattern; propodi rugose, margins serrated; dactyli slightly curved, terminating in corneous claw (Fig. 8F).

Male pleon and telson with reticulate pattern of fused granules; somites 3–5 fused, somite 6 longest; telson rounded (Fig. 8G). G1 slender, gently sinuous, tapering distally; terminal aperture with 2 lamellar folds; several long, thick simple setae located subdistally (Fig. 10P–R).

Colouration. Fresh specimen: Carapace, chelipeds and pereopods whitish, lower distal half of chela and proximal half of cheliped fingers with dark pigmentation (Fig. 2F).

Biology. The present specimen was collected from a rocky substrate in the vicinity of crinoids, at 56 m depth. Known to inhabit hard substrates covered with sand, reef slopes with overhangs and coral patches from 3–54 m depths (Mendoza & Ng 2008; Takeda & Komatsu 2018).

Remarks. Visayax osteodictyon was described by Mendoza & Ng (2008) from 4 males and 2 females collected at depths of 3–25 m from coral reef habitats in the Bohol Sea, Philippines. Mendoza & Ng (2008) differentiated this species from its only other congener Visayax estampadori Mendoza & Ng, 2008 in the distinct reticulation on the surface of the carapace and pereopods (Fig. 8A) (versus faint reticulation in the latter; Mendoza & Ng 2008: fig. 5A); ventrally deflexed frontal margin (Fig. 8A) (versus straight front in V. estampadori; Mendoza & Ng 2008: fig. 5C); smaller branchial tubercles (Fig. 8A) (versus larger in V. estampadori; Mendoza & Ng 2008: fig. 5A); narrow basal antennal article not reaching up to antennulary fossa (Fig. 8B) (versus broader basal article reaching up to antennulary fossa in V. estampadori; Mendoza & Ng 2008: fig. 6A); epistome with a slightly convex central region (Fig. 8B) (versus straight in V. estampadori; Mendoza & Ng 2008: fig. 6A); presence of a pigmented patch on the outer ventral surface of chela (Fig. 8E) (versus absent in V. estampadori; Mendoza & Ng 2008: fig. 5D); and G1 having a smaller terminal opening and less subterminal setae (Fig. 10P, Q) (versus larger terminal opening and more subdistal setae in V. estampadori; Mendoza & Ng 2008: fig. 6F, G). The Indian specimen conforms to the description of the holotype (Mendoza & Ng 2008) in the external reticulation, the nature of the basal antennal article, epistome and the presence of pigmented patch on the chela. However, the G1 of the Indian specimen (Fig. 10P, R) slightly differs from that of the holotype (Mendoza & Ng 2008: fig. 4F, G) in having a longer row of spinules on the inner margin.

Geographical distribution. Bohol Sea, Philippines (Mendoza & Ng 2008), Chichi-jima Island, Japan (Takeda & Komatsu 2018). The present observation is the first record of the genus and species from Indian Ocean indicating westward extension of the known geographical range.