Cavoportunus dubius ( Laurie, 1906 )

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 : 485-487

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.13228765
persistent identifier	https://treatment.plazi.org/id/03EA8791-7F22-FF83-FF79-FADBB64CD4C8
treatment provided by	Plazi
scientific name	Cavoportunus dubius ( Laurie, 1906 )
status

Treatment

Cavoportunus dubius ( Laurie, 1906) View in CoL

( Figs. 2D View FIGURE 2 , 6A–G View FIGURE 6 , 10I–L View FIGURE 10 )

Neptunus (Achelous) dubia Laurie 1906: 416 View in CoL , fig. 9 (type locality: Gulf of Mannar , Sri Lanka).

Portunus (Achelous) dubius View in CoL — Stephenson & Rees 1967: 4 (list) 20, fig 3a–b, pl. 2A.— Stephenson 1972a: 15, 38.— Stephenson 1972b: 135.— Stephenson 1976: 16.— Moosa 1981: 143 (list), 147.— Crosnier 1984: 401.— Crosnier 1985: 33, figs. 1a– e.— Zarenkov 1994: 115.— Moosa 1996: 521.— Poupin 1996: 31.— Neumann & Spiridonov 1999: 19.— Crosnier 2002: 404 View Cited Treatment .— Ng et al. 2008: 151 (list).

Portunus (Cycloachelous) yoronensis Sakai, 1974: 90 View in CoL .— Sakai 1976: 349, figs. 189a–d.— Ng et al. 2008: 151 (list).

Cavoportunus dubius View in CoL — Nguyen & Ng 2010: 41, figs. 1–4.— Komatsu 2011: 257, fig. 19C.—Mantellato et al. 2018: 192, 194, fig. 1.

Material examined. 1 male (26.9 × 20.4 mm) (IO/SS/BRC/00191), 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 hexagonal, 1.3 times as wide as long, dorsal surface glabrous; dorsal surface microscopically granular with distinct regions, bearing scattered granules; only metagastric ridge distinct, other ridges indistinct ( Figs. 2D View FIGURE 2 , 6A View FIGURE 6 ). Frontal margin with 4 teeth, projecting beyond tip of internal supraorbital angle; orbits relatively large, moderately dorsally inclined, supraorbital margin with single fissure, inner supraorbital margin rounded; infraorbital margin straight, granular, with forward-directed tooth; anterolateral margin with 9 teeth, first tooth largest, second to ninth teeth smaller; posterolateral junction of carapace rounded ( Fig. 6A View FIGURE 6 ).

Antennule folding obliquely; basal antennal article with lobe-like process, flagellum lodged in orbital hiatus ( Fig. 6B View FIGURE 6 ); epistome triangular, anterior and posterior margins elevated. Buccal cavity subquadrate; mxp3 merus subquadrate, shorter than ischium, anterolateral margin produced into rounded lobe ( Fig. 6C View FIGURE 6 ).

Cheliped 1.8 times as long as CL, merus with 4 spines on anterior margin, 1 distal spine on posterior margin ( Fig. 2D View FIGURE 2 ); carpus with long spine on inner angle; palm with 2 granular ridges on dorsal surface terminating in subdistal spines, short spine at carpal articulation, outer surface with 3 longitudinal granular costae on lower half; fingers slender, gently curved, as long as palm ( Fig. 6D, E View FIGURE 6 ). Pereopods 2–4 dactyli longer than propodi ( Fig. 2D View FIGURE 2 ); P5 merus posterior margin dentate, other segments unarmed ( Fig. 6F View FIGURE 6 ).

Male pleon triangular, somite 3 posterior margin with median cleft, somite 4 lateral margins convex, those of somite 5 slightly convex; telson small, triangular, 0.8 times as long as wide ( Fig. 6G View FIGURE 6 ). G1 stout, S-shaped; basal part relatively slender, subdistal portion distinctly dilated into a bluntly triangular lobe; distal tip with distinct folds ( Fig. 10I–K View FIGURE 10 ); G2 slender, tapering, 0.6 times as long as G1 ( Fig. 10L View FIGURE 10 ).

Colouration. Fresh specimen: Carapace white with densely-packed reddish reticulate markings on the dorsal surface, particularly the granules, granulated ridges and anterolateral spine tips ( Fig. 2D View FIGURE 2 ). Posterolateral carapace junction, edges of first two pleonites, outer carpal spine, outer carina and dorsal spine of the cheliped palm and dorsal surface of cheliped dactylus with silvery iridescence ( Fig. 2D View FIGURE 2 ).

Biology. The present specimens were collected along with gorgonians and sponges from coral reef habitat at 69 m depth. Known to inhabit coral reefs ( Nguyen & Ng 2010), on fine coral sand ( Stephenson and Rees 1967) at depths from 20–500 m ( Nguyen & Ng 2010).

Remarks. Cavoportunus dubius was originally described by Laurie (1906) from two males collected from the Gulf of Mannar and off Negombo, Sri Lanka. Stephenson & Rees (1967) reported Portunus dubius from the Philippines. Subsequently, Sakai (1974) described Portunus yoronensis from a male collected from Yoron Island, Japan. Crosnier (1984) and Nguyen & Ng (2010) synonymized Portunus (Cycloachelous) yoronensis Sakai, 1974 with Neptunus (Achelous) dubia Laurie, 1906 . Further, Nguyen & Ng (2010) transferred this species to a new genus, Cavoportunus , owing to the presence of two distinct depressions lateral to the sternal medial groove on the male sternum to accommodate a distinct G1 (with a swollen and bilobed subdistal part). The present specimen conforms to the morphology of the male pleon, third maxillipeds, left cheliped and G1 depicted by Laurie (1906: fig. 9). However, the carapace of the Indian specimen possesses densely packed fine reddish orange reticulation on the carapace ( Fig. 2D View FIGURE 2 ), as compared to reddish spots scattered on a white background in the Japanese specimen reported by Nguyen & Ng (2010: fig. 1).

Geographical distribution. Sri Lanka, Philippines, Japan, and French Polynesia ( Nguyen & Ng 2010). The present observation is the first record for Indian waters.

Kingdom	Animalia
Phylum	Arthropoda
Class	Malacostraca
Order	Decapoda
Family	Portunidae
Genus	Cavoportunus