Pleistacantha oryx Ortmann, 1893

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 : 85

Pleistacantha oryx Ortmann, 1893

( Fig. 14A–B )

Material examined. RV Hakuhō Maru KH-72-1 cruise, sta. 11 (Sulu Sea ; 08°12.7′N, 117°59.6′E – 08°11.8′N, 117°58.5′E; 285–306 m deep); 3 m beam trawl; 26 May, 1972; 1 ˁ ( CB 13.7 mm excluding branchial spinules; CL 18.3 mm excluding pseudorostral spines) , NSMT-Cr 28978.

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; 2 ˂˂ ( CB 9.3 mm; CL 6.4 mm; broken, soft shell) , NSMT-Cr 28993.

Remarks. Ng et al. (2008) listed 14 species in the genus Pleistacantha . Recently, two synonymous genera of Pleistacantha , Pleisticanthoides Yokoya, 1933 and Parapleisticantha Yokoya, 1933 , were reappraised as valid ( Ng and Richer de Forges, 2012; Richer de Forges et al., 2013). In addition, Pleistacantha kannu Ng, Ravinesh and Ravichandran, 2017 was described from the Indian Ocean, and Ahyong et al. (2019) recognized Echinoplax rubida Alcock, 1895 as a valid species of Pleistacantha . Consequently, the genus Pleistacantha at present consists of 12 species from the Indo-West Pacific region.

Pleistacantha oryx was confused with P. maxima Ahyong and Lee, 2006 , but distinguished by the pseudorostral spines which are broadly convex in lateral view, the less spinulate carapace surface, and the different G1 structure ( Ahyong and Lee, 2006). Otherwise, the smaller size at maturity can be a help to distinguish P. oryx from P. maxima .

Distribution. Most of the previous records of Pleistacantha oryx from Japan, the East China Sea, the Philippines and Australia were referred to those of P. maxima by Ahyong and Lee (2006), and therefore, the exact distributional range of P. oryx is uncertain at present. Although the distributional ranges of both species may widely overlap each other, the reliable records of P. oryx are only those by Ortmann (1893: Sagami Bay, 90–180 m deep) and Ahyong and Lee (2006: Sagami Sea, 540 m deep, and off Kaohsiung County, southern Taiwan).

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.