Trapezia tigrina Eydoux & Souleyet, 1842

(Fig. 5A–D)

Trapezia tigrina Eydoux et Souleyet, 1842: 232, pl. 2, fig. 4 (type locality: Hawaii).— Galil & Lewinsohn 1984: 166, fig. 1a–e.— Castro et al. 2004: 45 (key), 54, pl. 3E.— Castro 2009: 276, fig. 2B.

Trapezia danae Ward, 1939: 13, figs. 15, 16 (type locality: Samoa).— Serène 1969: 133, 135, fig. 4.

Trapezia wardi Serène 1969: 140, figs. 7, 12, 17, 18, 19.— Serène, 1971: 914, pl. 4C.— Sakai 1976: 509, pl. 181, figs. 3, 4.— Serène et al. 1976: 19.— Takeda & Nunomura 1976: 78.— Ribes 1978: 127.

Trapezia maculata Dana 1852: 256 (part).— Dana 1855, pl. 15, fig. 4b, 4c. [Non T. maculata (MacLeay, 1838)].— Alcock 1898: 221.

Trapezia ferruginea rufopunctata .— Paul’son 1875: 54, pl. 7, fig. 3, 3a. [Non T. rufopunctata (Herbst, 1799)]

Trapezia ferruginea maculata .— Bouvier 1915: 272 (95) (part). [Non T. maculata (MacLeay, 1838)]

Trapezia cymodoce maculata .— Edmondson 1962: 300, fig. 31b. [Non T. maculata (MacLeay, 1838)]

? Trapezia ferruginea maculata Lenz 1910: 553 .

? Trapezia cymodoce maculata Rathbun 1911: 235 .

Non Trapezia tigrina? Serène 1969: 133, fig. 4. [= T. flavopunctata Eydoux & Souleyet, 1842]

Material examined. 1 male (damaged specimen, not measured), 1 female (damaged specimen, not measured) (NIO /BOD/AB/BRY/00006), RVSS 6, west of Vijaydurg, Arabian Sea, 16.38°N, 72.12°E, 23 m depth, Van Veen grab, coll. R. Periasamy, 7 January 2014 .

Diagnosis. Carapace trapezoidal, smooth; frontal margins serrated with 2 low rounded median teeth, and larger, but low, lateral teeth; anterolateral margins with 2 long, acute spines (including external orbital angle) (Fig. 5A, C). Chelipeds smooth, slightly unequal, merus with 4 teeth on anterior margin, propodus with serrated lower margin (Fig. 5A, C). Pereopods 2–5 whitish, with large dark red spots (Fig. 5A–D). Male pleon T-shaped (Fig. 5B). Female pleon oval (Fig. 5D).

Colouration. Fresh specimen: carapace with 14 large dark red spots on yellowish background (Fig. 5A, C), chelipeds yellowish with large red spots on outer surfaces of carpus and merus (Fig. 5C, D).

Biology. The present specimens were collected from rocky substratum, at 23 m depth, covered with macroalgae. Trapezia tigrina is known to be an obligate symbiont of Pocillopora elegans (Castro 1997), inhabits dead corals of the genera Acropora (Head et al. 2015) and Stylophora, as well as coral rubble and sandy substratum (Castro et al. 2004); down to 45 m (Castro 1997). Its known predators include the hawkfish, Paracirrhites arcatus (Cuvier, 1829) (Leray et al. 2012) .

Trapeziid crabs protect their host by removing sediment from coral tissue (Stewart et al. 2006), repulse predation by seastars (Glynn 1976), and enhance physical growth and mucus production (Glynn 1983).

Remarks. Trapezia tigrina was originally described from Hawaii (Eydoux & Souleyet 1842). Galil & Lewinsohn (1984) re-described T. tigrina to resolve the taxonomic ambiguities and provided a comprehensive synonymy. Serène (1984) provided a key to the species of the genus Trapezia . The present specimens are juveniles and conform to the description provided by Galil & Lewinsohn (1984) in the short, rounded frontal teeth, smooth ventral surfaces of the chelipeds, and the presence of red spots on the carapace, chelipeds and pereopods.

Geographical distribution. Throughout the Indo-West Pacific region (Castro 1997). In India, reported from Andaman archipelago (Alcock 1898) and Minicoy Island (Borradaile 1902b; Sankarankutty 1961); eastern Arabian Sea off India (present study).