Pachygrapsus fakaravensis Rathbun, 1907

Poupin, Joseph, Davie, Peter J. F. & Cexus, Jean-Christophe, 2005, A revision of the genus Pachygrapsus Randall, 1840 (Crustacea: Decapoda: Brachyura, Grapsidae), with special reference to the Southwest Pacific species, Zootaxa 1015 (1), pp. 1-66: 12-15

publication ID 10.11646/zootaxa.1015.1.1

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Pachygrapsus fakaravensis Rathbun, 1907


Pachygrapsus fakaravensis Rathbun, 1907   ( Figures 3a–f View FIGURE 3 ; 14a View FIGURE 14 ; 15a View FIGURE 15 )

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 View Materials )   .

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 View Materials ); 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 View Materials )   . — 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   )   .


Carapace subquadrate; lateral margins almost parallel with no tooth behind exorbital angle ( Fig. 3a View FIGURE 3 ). Dorsal surface weakly convex with strong transverse striae with setae. Front 0.5 times carapace width at exorbital angles; anterior margin sinuous ( Fig. 3b View FIGURE 3 ). Infraorbital margin dentate along entire length, separated from outer orbital tooth by deep notch ( Fig. 14a View FIGURE 14 ).

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 View FIGURE 3 ). 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 View FIGURE 3 ). 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 View FIGURE 3 ). Female with several short setiferous striae on abdominal tergites ( Fig. 3f View FIGURE 3 ). G1 with long, horn­like process with minute spinule medially ( Fig. 15a View FIGURE 15 ).

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.


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

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 View FIGURE 15 ).

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 View FIGURE 15 ). 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 View FIGURE 3 , 1d View FIGURE 1 ).

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).


Museum National d'Histoire Naturelle


Smithsonian Institution, National Museum of Natural History














Pachygrapsus fakaravensis Rathbun, 1907

Poupin, Joseph, Davie, Peter J. F. & Cexus, Jean-Christophe 2005

Pachygrapsus fakaravensis

DeFelice, R. & Eldredge, L. & Carlton, J. 2001: 45
Ng, P. K. L. & Wang, C. H. & Ho, P. H. & Shih, H. T. 2001: 40
Davie, P. J. F. 1998: 63
Poupin, J. 1994: 62
Monteforte, M. 1984: 172
Hwang, J. J. & Yu, H. P. 1980: 153
Sakai, T. 1976: 636
Tesch, J. J. 1918: 76
Rathbun, M. J. 1907: 29