Pleisticanthoides simplex ( Rathbun, 1932 )

Takeda, Masatsune, Ohtsuchi, Naoya & Komatsu, Hironori, 2021, Crabs (Crustacea, Decapoda) from the Sea off East and Southeast Asia collected by the RV Hakuhō Maru (KH- 72 - 1 Cruise) 1. Sulu Sea and Sibutu Passage, Bulletin of the National Museum of Nature and Science. Series A, Zoology 47 (2), pp. 65-97 : 86-87

Pleisticanthoides simplex ( Rathbun, 1932)

( Fig. 14C )

Material examined. RV Hakuhō Maru KH-72-1 cruise, sta. 20 (Sibutu Passage; 05°40.9′N, 119°46.3′E – 05°43.1′N, 119°47.0′E; 460–514 m deep); otter trawl; 10 June, 1972; 1 ˁ ( CB 5.9 mm; CL 8.2 mm excluding pseudorostral spines) , NSMT-Cr 28979.

Description of a male from the Sibutu Passage. Carapace pyriform, dorsal surface covered with long hooked setae, posterior surface sparsely covered with granules, gastric, hepatic, anterior cardiac regions smooth; regions well-defined: gastric region slightly elevated; branchial region inflated, separated from cardiac, gastric regions by deep groove. Front with 2 sharp, short, diverging pseudorostral spines; pseudorostral spine basally with 4 sharp accessory spines (1 on ventolateral surface, 3 directed anteriorly); supraocular eave fringed with 5 spines (anterior 3 long, posterior 2 short); postocular spine strong, with small accessory spines anteriorly, dorsally, posteriorly; interocular spine strong, directed dorsally, proximally with small spine; subhepatic region weakly inflated, with long spine bearing some accessory spines, followed by 4 long spines bearing stiff setae (shorter than supraocular tooth). Eyestalk relatively long, slender, subdistally with small spine ventrally; cornea rounded, diameter greater than that of peduncle. Inter-antennular spine (=true rostrum) pointed downwards, medially divided by U-shaped concavity to form 2 spines. Antennae almost twice as long as pseudorostral spines; basal antennal article slender, fused with carapace, with long, sharp spine on distolateral angle; urinary article with large green gland opening, surrounded by raised rounded margin, outer border with strong flattened triangular tooth. Epistome smooth; buccal frame quadrangular. Third maxilliped with segments flattened, covered with long setae; outer border of carpus crenulated.

Chelipedal merus moderately inflated, dor- somesial margin armed with long, sharp spines. Carpus globular. Chela inflated, with 6 spines on dorsal surface, row of 7 strong spines on outer surface, row of 4 spines on inner surface, immovable finger, dactylus smooth on surface.

Ambulatory legs conspicuously long, length decreasing posteriorly. Meri and carpi with row of long hooked setae and/or long stiff setae. Propodi and dactyli with row of very long, relatively rigid setae on flexor surface.

Male pleon with 6 free pleomeres and telson, covered with subacute granules and long stiff setae; pleomeres 4–5 with large, elongated median tubercle on distal margin; pleomere 6 with distolateral margins not expanded; telson with rounded distal margin. G1 curved in entire length, distal third dorsolaterally flattened.

Remarks. The genus Pleisticanthoides was established by Yokoya (1933) for this species by monotypy. This genus had once synonymized with Pleistacantha Miers, 1879 by Sakai (1938), but recently, Ng and Richer de Forges (2012) recognized Pleisticanthoides as a distinct genus from Pleistacantha and added two species from the Philippines, Papua New Guinea, and Vanuatu to this genus. The genus Pleistacanhoides is distinguished from Pleistacantha by 1) the carapace dorsal surface with few spinules or setae (versus with numerous spines in Pleistacantha ), 2) the margins of the meri and propodi of the second to fourth ambulatory legs lined with only stiff setae (versus lined with hard spines, spinules and stiff setae in Pleistacantha ), and 3) the G1 evenly curved, with the distal third dorsoventrally flattened, and without trace of a subdistal process (versus the relatively slender and straight, distal third is evenly cylindrical and there is a recurved process just before the tip in Pleistacantha ).

The present specimens generally agree with the description and illustrations given by Yokoya (1933) and Ng and Richer de Forges (2012), and keyed out correctly to l Pleistacantha simplex z following Ahyong et al. (2005). The distinguishing characters of Pleisticanthoides simplex from the other two congeners were discussed by Ng and Richer de Forges (2012), and recently, Takeda and Komatsu (2020) recorded a pair of specimens from Amami-Oshima Island in the northern Ryukyu Islands, ca. 200 m deep.

Distribution. This species is known from Japan (from Sagami Bay to Amami-Oshima Island) ( Sakai, 1976; Ng and Richer de Forges, 2012; Takeda and Komatsu, 2020), and the Sulu Sea and Indonesian waters ( Griffin and Tranter, 1986). The known bathymetric range is from 60 to 540 m.

Figures

Fig. 14. A, B: Pleistacantha oryx Ortmann, 1893, male (NSMT-Cr 28978. CB 13.7mm; CL 18.3mm excluding pseudorostral spines) in dorsal (A) and lateral (B) views. C: Pleisticanthoides simplex (Rathbun, 1932), male (NSMT-Cr 28979. CB 5.9mm; CL 8.2mm) in dorsal view.