New Records of Spider Crabs of the Genera Cyrtomaia Miers, 1886, and Platymaia Miers, 1886 (Decapoda: Majoidea: Inachidae) from the Andaman Sea, Thailand

Phuket mar. biol. Cent. Res. Bull. 70: 7–14 (2011)

NEW RECORDS OF SPIDER CRABS OF THE GENERA CYRTOMAIA MIERS, 1886, AND PLATYMAIA MIERS, 1886 (DECAPODA: MAJOIDEA: INACHIDAE) FROM THE ANDAMAN SEA, THAILAND

Rueangrit Promdam

Department of Biology, Faculty of Science, Prince of Songkla University, Hatyai, Songkhla 90112, Thailand Email: [email protected]

ABSTRACT Two species of deep-water spider crabs, Cyrtomaia suhmii Miers, 1886, and Platymaia alcocki Miers, 1886, based on the materials of the BIOSHELF Project (1996–2000) are recorded for the first time from Thailand. It is also the first record of these two genera from the Andaman Sea coast of Thailand. Adult and juvenile forms of C. suhmii collected from the same locality confirm that C. curviceros Bouvier, 1915, is a junior synonym, the characters previously used to separate them explained by size and age.

Key words: new records, spider crabs, Decapoda, Majoidea, Inachidae, Cyrtomaia, Platymaia, Thailand

INTRODUCTION TAXONOMY

Two rare spider crabs, Cyrtomaia suhmii Family Inachidae MacLeay, 1838 Miers, 1886, and Platymaia alcocki Miers, 1886, Genus Cyrtomaia Miers, 1886 were collected by the R.V. Chakratong Tongyai Cyrtomaia suhmii Miers, 1886 from the Andaman Sea during the BIOSHELF (Figs. 1, 2A–F) project surveys of the west coast of Thailand in 1996–2000. Based on Ng and Davie (2002), and Cyrtomaia suhmii Miers, 1886: 16, pl. 3, fig. 2, Naiyanetr (2007), the species as well as the genera 2a–2c; Rathbun, 1918: 6; Richer de had not been previously reported from Thai Forges and Guinot, 1990: 525; Richer de waters. The present report serves to formally Forges and Ng, 2007: 56 (list); Ng et al., record these species, as well as to discuss variation 2008: 111 (list). in adult and juvenile specimens. Cyrtomaia suhmi - Rathbun, 1893: 230; Griffin, 1974: 9; Guinot and Richer de Forges, MATERIALS AND METHODS 1982a: 1096; 1982b: 21, fig. 10, 11A–B, 23B; Griffin and Tranter, 1986b: 352, figs. Specimens examined are deposited in the 1, 2; Richer de Forges and Guinot, 1988: Reference Collection of Phuket Marine Biological 42–43 fig. 2B, C, pl. 2F–G; Poore, 2004: Center (PMBC). All measurements provided are 360; 361 fig. 108. pre-rostral lengths and carapace widths Cyrtomaia Suhmi var. curviceros Bouvier, 1915b: respectively. For details on all BIOSHELF stations, 9–15, pls. 1. see Aungtonya et al. (2000). The classification Cyrtomaja suhmi typica Serène and Lohavanijya, used here follows Ng et al. (2008). 1973: 46 (in key). 8 Phuket mar. biol. Cent. Res. Bull.

Figure 1. Cyrtomaia suhmii, adult male (60.2 × 67.1 mm) (PMBC 19999), dorsal view of whole animal. Scale = 20 mm.

Cyrtomaja suhmi curvicornis Serène and 488 m, coll. S. Bussarawit and C. Aungtonya, Lohavanijya, 1973: 45, 46 (in key). 06.02.1999; PMBC 20000, 2 juv. (11.8 × 11.5 mm, Cyrtomaia curviceros Sakai, 1976: 181; Guinot and 8.6 × 8.2 mm), BIOSHELF St. J10, 0715Ń, Richer de Forges, 1982a: 1096; 1982b: 09715É, Agassiz trawl, 695–683 m, coll. C. 24, fig. 12A–D; Richer de Forges and Aungtonya & V. Vongpanich, 19.02.2000; PMBC Guinot, 1988: 42–43, fig. 2A; Ng et al., 19929, 1 juv. (7.7 × 7.4 mm), 1 female (56.3 × 2001: 13; 81 fig. 3h; Richer de Forges 61.2 mm), BIOSHELF St. L10, 0645Ń, 09723É, and Ng, 2007: 56 (list). Agassiz trawl, 707–651 m, coll. C. Aungtonya & not Cyrtomaia suhmi - Griffin and Brown. 1976: V. Vongpanich, 21.02.2000 252, fig. 6; Griffin and Tranter, 1986a: 30, fig. 91g [= C. griffini Richer de Diagnosis Forges and Guinot, 1990]. Carapace smooth, not granular or not Cyrtomaia suhmi typica Doflein, 1904 : 54– spinulate, with 2 long, subparallel protogastric 55, pl. 19: figs. 1, 2 [= C. gaillardi Guinot spines. Pseudorostral spine divergent, arched. and Richer de Forges, 1982]. Basal antennal article cylindrical, armed with 3–5 spines (include internal spine). Orbital border Material examined smooth, intercalated orbital granule present (in PMBC 19999, 1 male (60.2 × 67.1 mm), young) or absent, without preocular spines (in BIOSHELF St. E8, 0832Ń, 09604É, Otter trawl, adults). Ocular spine blunt. 9 New records on spider crabs

Figure 2. Cyrtomaia suhmii: A–C, juvenile (11.8 × 11.5 mm) (PMBC 20000); D–F, adult male (60.2 × 67.1 mm) (PMBC 19999); A, D, dorsal view; B, E, anterior part of carapace showing rostrum; C, F, lateral view of carapace. Scale = 10 mm.

Distribution Remarks Indo-West Pacific: Japan, Philippines, Cyrtomaia suhmii was described by Miers Indonesia, Australia, Thailand (Andaman Sea) and (1886) on the basis of an imperfect crushed young India. male specimen collected from Talaud Islands (Tulur 10 Phuket mar. biol. Cent. Res. Bull.

Islands) (see Guinot & Richer de Forges 1982b: are similar to the original description and figure of 22, fig. 10), Indonesia, by the Challenger C. suhmii by Guinot and Richer de Forges (1982b: Expedition. Subsequently, Cyrtomaia suhmii 22, 23, fig. 10, 11A, B), especially with regards to curviceros Bouvier, 1915, was described from Japan the protogastric spines which are divergent (Miers, and recognized as a distinct species by Sakai 1886: 16, pl. 3, fig. 2). On the other hand, large (1976). The status of C. curviceros has long been male specimens resemble C. curviceros (Fig. 1, uncertain. Griffin and Tranter (1986) treated both 2D–F), although the number of the spines on the names as synonyms, while Richer de Forges and basal antennal article is slightly different. This Guinot (1982a, 1988) argued that it may be a good difference, however, is not significant and can species. Ng and Huang (1997) treated Taiwanese easily be explained by variation. The present series material of the species as C. curviceros (see also of specimens confirm that the differences which Ng et al., 2001), and until recently, was still have been observed in the past between these two regarded as a distinct species (see Richer de Forges species are due to size and age, and that C. suhnii and Ng, 2007). In their annotated checklist of extant curviceros Bouvier, 1915, clearly is a junior brachyuran crabs of the world, Ng et al. (2008) synonym of C. suhmii Miers, 1886. treated C. suhmii curviceros as a synonym of C. suhmii but without comments. Examination of Genus Platymaia Miers, 1886 more material of other allied species like C. griffini Richer de Forges & Ng, 1990, has shown that the Platymaia alcocki Rathbun, 1916 characters used to separate C. curviceros from C. (Figs. 3, 4A–F) suhmii are not valid at the species level (P. K. L. Ng, pers. comm., see also Richer de Forges and Platymaia wyville-thomsoni. - Wood-Mason and Ng, 2008). Alcock, 1891: 258; Alcock, 1895: 181– Specimens of various sizes were collected 182; Doflein, 1904: 59–69, 160–165, figs. from the same Thai locality. The young specimens 2–6; pls. 2, 20–23, 39, 43: figs. 5, 6; pl.

Figure 3. Platymaia alcocki, adult male (71.0 × 77.5 mm) (PMBC 20367), dorsal view of whole animal. Scale = 20 mm. 11 New records on spider crabs

Figure 4. Platymaia alcocki: A–C, adult male (71.0 × 77.5 mm); D–F, young male (25.9 × 30.4 mm) (PMBC 20367); A, D, dorsal view; B, E, anterior part of carapace showing rostrum; C, F, lateral view of carapace. Scale = 10 mm.

50: figs. 2, 5, 6 [not Platymaia wyville- 1986a: 48 (Pl. 4b; figs. 10a, b; 11c); thomsoni Miers, 1886]. 1986b: 357; Takeda and Webber, 2006: Platymaia alcocki Rathbun, 1916: 530; 1918: 8; 194. Serène and Lohavanijya, 1973: 48 (in key); Not Platymaia alcocki - Takeda and Miyake, 1969: Griffin, 1974: 27; Griffin and Tranter, 498–500, figs. 10a, b, 11a–c; Sakai, 1976: 12 Phuket mar. biol. Cent. Res. Bull.

176–177, fig. 94a; Dai and Yang, 1991: Remarks 120 [=Platymaia wyville-thomsoni Miers, Platymaia alcocki can sometimes be 1886]. misidentified with P. wywillethomsoni because young and juveniles of P. alcocki also have Material examined prominent spines on all the carapace regions PMBC 20367, 4 male (71.0 × 77.5 mm, 25.9 × (Alcock, 1895). Although all the spines on the 30.4 mm, 20.6 × 22.7 mm, 20.2 × 22.8 mm), 5 dorsal carapace surface of adult P. alcocki are female (19.4 × 21.4 mm, 19.0 × 21.4 mm, 19.0 × reduced to only tubercles (Fig. 4A–C), adult P. 22.1 mm, 18.7 × 21.2 mm, 18.4 × 20.3 mm), wywillethomsoni are still armed with one or two BIOSHELF St. J8, 0715´N, 09730´E, Agassiz spines on each side of the protogastric regions trawl, 490–479 m, coll. S. C. Aungtonya & V. even as adults (Griffin and Tranter, 1986a: 307, Vongpanich, 18.02.2000 fig. 5b). The main diagnostic feature of P. alcocki is the deep groove on each side of mesogastric Diagnosis region, which separates the two adjacent branchial Carapace tranversly subcircular, surface regions (Rathbun, 1916) (Fig. 4A, D). This nearly smooth in adults, rostral spine subequal to character is useful even for young and adult interantennular spine, preocular spine absent; specimens of P. alcocki and is clearly evident on protogastric ridge with 2 tubercles, lacking spines the series of Thai specimens here. (in adults); groove on each side of mesogastric region deep, clearly separating adjacent branchial ACKNOWLEDGEMENTS regions; palm of male chelipeds more than twice as long as high, distally increasing in width; The author would like to thanks Peter K. propodus of ambulatory legs flattened, 7.5 times L. Ng of the Raffles Museum of Biodiversity width of fourth ambulatory leg. Research, National University of Singapore, for reviewing the manuscript. Distribution Indian Ocean: Andaman Sea to eastern Africa

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Manuscript received: 9 February 2011 Accepted: 1 August 2011