Henicoplax maldivensis (Rathbun, 1902)

Ng, Peter K. L., Priyaja, P., Kumar, A. Biju & Devi, S. Suvarna, 2019, A collection of crabs (Crustacea, Brachyura) from the southwestern coast of India, with a discussion of the systematic position of Nectopanope Wood-Mason in Wood-Mason & Alcock, 1891 (Euryplacidae), ZooKeys 818, pp. 1-24 : 9-11

Henicoplax maldivensis (Rathbun, 1902) Figs 5, 7 F–H

Goneplax maldivensis Rathbun, 1902: 124, figs 3-5; Guinot 1969: 518; Castro 2007: 686, 687 [list].

"?[ Goneplax ] maldivensis ": Guinot 1971: 1081 [list].

Otmaroplax maldivensis : Števčić 2005: 134 [genus name nomen nudum]

" Heteroplax " maldivensis : Ng et al. 2008: 78, 79 [in list].

Henicoplax maldivensis : Castro and Ng 2010: 61, figs 22 A–E, 24 D–F.

Material examined.

1 male (9.9 × 6.3 mm), 7°27.978'N, 77°32.297'E, 100 m.

Remarks.

Henicoplax Castro & Ng, 2010, was established for Indo-West Pacific species that had been previously classified in Goneplax Leach, 1814, or Heteroplax Stimpson, 1858. Five species are currently recognised: H. eriochir Castro & Ng, 2010, H. maldivensis (Rathbun, 1902) [type species], H. nitida (Miers, 1879a), H. pilimeles Castro & Ng, 2010, and H. trachydactylus Castro & Ng, 2010.

The present specimen is clearly H. maldivensis as redescribed and figured at length by Castro and Ng (2010: 61). The species was previously known only from the holotype male (7.4 × 4.8 mm) obtained from Gan Island in Addu Atoll in the Maldives. The present male differs from the type male in having the frontal margin slightly more sinuous and the cleft between the external orbital tooth and the anterolateral tooth is more U-shaped (Fig. 5A, B) (versus frontal margin almost straight and the lateral carapace cleft being V-shaped in the holotype; cf. Castro and Ng 2010: fig. 22A); and while the G1 shape is similar, the distal spination is relatively less pronounced and the tip is sharply tapering (Fig. 7F, G) (versus distal half with relatively more spines and the tip is subtruncate in the holotype; cf. Castro and Ng 2010: fig. 24D, E). The differences are not substantial and can easily be explained by variation and size, the present male (9.9 × 6.3 mm) being larger than the type (7.4 × 4.8 mm).

Castro and Ng (2010) showed that records of " H. nitida " from the Andaman Sea should be referred to a new species, H. pilimenes ; and indicated that true H. nitida should be restricted to East Asia. The records of " H. nitida " from the Gulf of Martaban (south of Myanmar) and off Madras in India by Henderson (1893: 379) are almost certainly not this species. The Myanmar material is probably H. pilimenes , while that from India may be this species or even H. maldivensis instead. Specimens will need to be re-examined to be certain.

Heteroplax maldivensis is thus far known for certain only from the Maldives ( Rathbun 1902; Castro and Ng 2010) and the present specimen represents the first confirmed presence of this species in India.