A revision of the genus Pachygrapsus Randall, 1840 (Crustacea: Decapoda: Brachyura, Grapsidae), with special reference to the Southwest Pacific species Author Poupin, Joseph Institut de Recherche de l'Ecole Navale, IRENav BP 600, 29240 BREST NAVAL France (poupin @ ecolenavale. fr; cexus @ ecole-navale. fr) Queensland Museum, P. O. Box 3300, South Brisbane, Queensland, Australia (peter. davie @ qm. qld. gov) poupin@ecolenavale.fr Author Davie, Peter J. F. Author Cexus, Jean-Christophe Institut de Recherche de l'Ecole Navale, IRENav BP 600, 29240 BREST NAVAL France (poupin @ ecolenavale. fr; cexus @ ecole-navale. fr) Queensland Museum, P. O. Box 3300, South Brisbane, Queensland, Australia (peter. davie @ qm. qld. gov) poupin@ecolenavale.fr text Zootaxa 2005 2005-07-05 1015 1 1 66 https://biotaxa.org/Zootaxa/article/view/zootaxa.1015.1.1 journal article 10.11646/zootaxa.1015.1.1 1175­5334 5049232 67DBD7AA-FA11-4F32-811B-0A9EFF4C668F Pachygrapsus fakaravensis Rathbun, 1907 ( Figures 3a–f ; 14a ; 15a ) Pachygrapsus fakaravensis Rathbun, 1907: 29 , pl. 5, fig. 1, pl. 9, fig. 6, 6a [ type locality: Fakarava Atoll, Tuamotu Archip., French Polynesia ]. Tesch, 1918: 76 (Key). — Sakai, 1976: 636 , pl. 218, fig. 3 ( Japan ). — Hwang & Yu, 1980: 153 , pl. 11­2 (Taiwan). — Monteforte, 1984: 172 , annex I, tab. a (Tuamotu Archip.). — Poupin, 1994: 62 , fig. 58, pl. 7e (Tuamotu Archip.). — Davie, 1998a: 63 (Hawaiian Is.). — DeFelice et al ., 2001: 45 (Hawaiian Is.). — Ng et al ., 2001: 40 , fig. 8e (Hawaiian Is., Taiwan ; references). Type material Male holotype , 18.0 x 19.4 mm ( USNM 32844 ) . Material Examined French Polynesia . Tuamotu Archip. : Fakarava Atoll , outer reef, coll. USS Albatross , 12 October 1899 , M holotype 18.0 x 19.5 mm ( USNM 32844 ); Taiaro Atoll , outer reef, low tide at night, on big coral rocks, Taiaro Expedition , coll. J. Poupin , 12–20 February 1994 , 1 ov. F 15.0 x 16.5 mm ( MNHN B25782) . — Hawaiian I. : Milolii , intertidal on rocks at night, coll. G. Paulay , 31 October 1997 , 1 ov. F. 12.9 x 15.1 mm ( UF 2255 ; erroneously labelled P. plicatus ) . Diagnosis Carapace subquadrate; lateral margins almost parallel with no tooth behind exorbital angle ( Fig. 3a ). Dorsal surface weakly convex with strong transverse striae with setae. Front 0.5 times carapace width at exorbital angles; anterior margin sinuous ( Fig. 3b ). Infraorbital margin dentate along entire length, separated from outer orbital tooth by deep notch ( Fig. 14a ). Chelipeds equal. Merus with deep transverse striae with setae; dorsal, anterior margins with few mobile spines, inner ventrodistal lobe with 3–4 teeth. Carpus with few granules, short striae with setae; inner spine stout, blunt. Outer face of chela with several longitudinal striae formed by rounded tubercles with setae on lower half; upper half with rounded granules surrounded by setae ( Fig. 3c ). Tips of fingers spoon­like, glabrous. Meri of ambulatory legs with deep transverse to oblique ridges with setae; lower margin of P5 meri without sub­median tubercle ( Fig. 3d ). Carpi, propodi with two longitudinal striae with setae. Dactyli ending in strong corneous claw; dorsal, ventral margins with rows of strong, moveable spines. Male with numerous short setiferous striae on abdominal tergites, thoracic sternites; sixth somite of abdomen plus telson triangular ( Fig. 3e ). Female with several short setiferous striae on abdominal tergites ( Fig. 3f ). G1 with long, horn­like process with minute spinule medially ( Fig. 15a ). Colour: overall brown to dark brown with violet hues and paler areas on ambulatory legs. Measurements: carapace of specimens examined ranging from 12.9 x 15.1 to 15.0 x 16.5 mm . Distribution West and Central Pacific . Japan ; Taiwan , Hawaiian Is., French Polynesia (Tuamotu Archip.: Fakarava, Makatea, Mataiva, Taiaro, Takapoto). Habitat Collected at upper level of reefs at night; uncommon. Remarks FIGURE 3. Pachygrapsus fakaravensis Rathbun (1907) . a) dorsal view; b) front; c) left chela, outer face; d) right P5; e) male abdomen; f) female abdomen. a, b, d, f, ov. female 15.0 x 16.5 mm (MNHN B25782); c, e, holotype male 18.0 x 19.4 mm (USNM 32844). Pachygrapsus fakaravensis is uncommon, rarely reported in the literature. It is morphologically close to the Indo­West Pacific P. plicatus (H. Milne Edwards, 1837 ) , which has similar coarse striations on the carapace and the same longitudinal striae on the outer face of the chelae. The two species have been collected together in French Polynesia . They can be separated by the shape of the lateral carapace margins (subparallel in P. fakaravensis , posteriorly convergent in P. plicatus ), the presence of setae on the longitudinal striae of the outer face of the chelae of P. fakaravensis , and by the abdominal tergites having short striae in P. fakaravensis but being smooth in P. plicatus . The shape of the G1, figured here for the first time for P. fakaravensis , also separates the two species ( Fig. 15a, e ). After examining P. corrugatus (von Martens, 1872 ) from the west and central Atlantic ( USNM 72340, 122786, 252325), it is clear that P. fakaravensis is morphologically close to the latter and may thus be considered a sibling species. It is surprising that neither Rathbun (1907) in her description of P. fakaravensis , nor Manning & Chace (1990) in recording and illustrating a male of P. corrugatus from Ascension I., mentioned this sharp similarity. Both species share a subrectangular carapace, with almost parallel lateral margins; coarse and hairy striae on the carapace; several longitudinal striae furnished with setae on the outer face of the chelae; abdominal tergites with short transverse striae; similarly shaped infraorbital margins, with a small protrusion distally followed by a deep indentation; and similar G1 ( Fig. 15a, f ). The two species can, however, easily separated using the relative striation of the abdominal tergites, which is more pronounced in P. fakaravensis than in P. corrugatus . This difference is especially obvious in males. Striae are also present on the thoracic sternites of P. fakaravensis but absent in P. corrugatus ( Fig. 3e , 1d ). Davie (1998a) suggested that it was likely that P. fakaravensis had only recently become established or possibly introduced in the Hawaiian Is. because it was unusual that such a relatively large and distinctive intertidal crab, living in a major harbour on the island of Oahu, had not been previously noticed, especially given the large collections reported by Rathbun (1906) and the extensive collections made by Edmondson (1959) .