Pachygrapsus crassipes Randall 1840
Creators: name: Poupin, Joseph
name: Davie, Peter J. F.
name: Cexus, Jean-Christophe
Publisher: name: Zenodo
Year: 2005
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Malacostraca
Decapoda
Grapsidae
Pachygrapsus
Pachygrapsus crassipes

description: Pachygrapsus crassipes Randall, 1840 (Figures 2a–e, 14g, 15g, 16)   
 Pachygrapsus crassipes Randall, 1840: 127 [type locality: Hawaiian Is. but according to Rathbun (1918) and Edmonson (1959) this locality must be erroneous]. — Stimpson, 1858: 48 [102] (California, Japan); 1907: 116 (Japan). — Ortmann, 1894: 708 (California; Japan). — Rathbun, 1918: 241 (California; Galápagos Is., Japan, Korea; but not Chile, see distribution). — Tesch, 1918: 76 (Key). — Garth, 1957: 103 (invalid record in Chile; see distribution). —Edmonson, 1959: 168 (California). — Sakai, 1976: 634, pl. 218, fig. 1 (Japan, Korea; references). — Dai & Yang, 1991: 511 (China sea, Guangdong, Fujian, and Zhejiang). — Hendrickx, 1995: 140 (east Pacific from Oregon to Gulf of California and Rocas Alijos; references). — Cuesta & Schubart, 1998: 1501 (California). — Ng et al., 2001: 40 (Taiwan; references).   
 Grapsus eydouxi H. Milne Edwards, 1853: 170 [136] (Chile; probably an erroneous locality, see distribution).   
 Leptograpsus gonagrus H. Milne Edwards, 1853: 173 [139] (type locality unknown).   
 Type material Male preserved in alcohol (ANSP CA 901) (P. Callomon, pers. comm.).   
 Material Examined   
 East Pacific. California: Pacific Grove, 1 M 27.0 x 30.8 mm (MNHN B12892); coll. J. E. Benedict, June 1905, 3 M 26.5 x 29.8–37.2 x 42.9 mm, 4 ov. F 27.3 x 30.1–31.9 x 36.8 mm, 2 F 25.6 x 28.4, 34.0 x 39.6 mm, plus numerous other specimens not examined (USNM 32234). West Pacifi c. Japan: Enoshima, Sagami Bay, coll. M. Takeda, 15 August 1980, 1 M 31.9 x 36.6 mm (NSMT Cr7516). — Sotobo, Chiba Prefecture, coll. T. Habe, 25 March 1975, 2 M 16.8 x 18.9, 24.9 x 29.3 mm (NSMT Cr 6822).   
 Diagnosis   
Carapace with dorsal surface weakly convex, striated on gastric, hepatic, branchial regions; striae without setae. Cardiac, intestinal regions smooth or only with faint striae. Lateral margins convergent posteriorly, with single tooth behind exorbital angle (Fig. 2a). Front 0.6 times exorbital width, anterior margin slightly sinuous with 2 lobules distally (Fig. 2b). Infraorbital margin weakly dentate on inner half, deeply dentate on outer half; outer notch deep (Fig. 14g).  
Outer face of chelae smooth with faint longitudinal line near lower margin, becoming clearly noticeable only on outer face of fixed finger; upper margin slightly carinated; tip of fingers spoon­like, glabrous (Fig. 2c). Ambulatory legs almost totally glabrous; carpi, propodi with several short mobile spines; dactyli with longitudal rows of long mobile spines, ending with strong, corneous claw. Lower margin of P5 merus smooth with rounded distal angle (Fig. 2d).  
Abdominal tergites smooth; sixth somite of abdomen plus telson triangular in male (Fig. 2e). G1 bluntly truncated with small horn­like process distally (Fig. 15g).  
Colour: very variable on photographs examined. Carapace green to almost totally black. Chelipeds light pink to purple or black, with a marbled pattern on the chelae. Ambulatory legs light green or purple to almost totally black.  
Measurements: large size; carapace of specimens examined ranging from 26.5 x 29.8 mm to 37.2 x 42.9 mm.  
 Distribution   
 East Pacific. Oregon and California, Mexico, Galápagos. West Pacific. China, Japan, Korea, Taiwan.   
 The type locality given by Randall (1840), the Hawaiian Is., is certainly erroneous as this large­size and common species has never again been recorded from the islands. The type specimen was most probably collected on the California coast. Pachygrapsus crassipes was also listed as occurring in Chile by Rathbun (1918: 241) based on the fact that this is the type locality given for Grapsus eydouxi H. Milne Edwards (1853: 170). The type of G. eydouxi has not been found at the MNHN. Garth (1957: 105) considered the type locality of Chile for G. eydouxi to be erroneous, and thus he did not include P. crassipes as part of the Chilean fauna.   
 Habitat Intertidal on rocky shores.   
 Remarks   
 Pachygrapsus crassipes, together with P. gracilis, P. laevimanus, P. loveridgei, P. maurus, and P. transversus, belongs to the group of species with only one tooth behind the exorbital angle. It clearly differs from these species by the shape of its G1 (Fig. 15). Of this group it is morphologically close to P. transversus, another large­size species. The two can be separated by the presence of striae on the cardiac and intestinal regions of the carapace being marked only in P. transversus (Fig. 2a, 13a); the longitudinal stria on the outer face of the chela is unclear in P. crassipes, but deep in P. transversus (Fig. 2c, 13c); the ventrodistal angle of the P5 merus is rounded in P. crassipes, but it has spines in P. transversus (Fig. 2d, 13d); and the male abdomen is regularly triangular at its tip only in P. crassipes (Fig. 2e, 13e).   
 Pachygrapsus crassipes is common on the Pacific coasts of North and South America from Oregon to Mexico and the Galápagos Is. Stimpson (1907: 116) was the first to record it from the west Pacific, indicating that he was “unable to find a distinguishing character, however minute, between the specimens from Japan and those from California”. Pachygrapsus crassipes was reported several times thereafter from the west Pacific, including Korea (Rathbun, 1918), Japan (Sakai, 1976), China (Dai & Yang, 1911), and Taiwan (Ng et al., 2001). This amphi­Pacific distribution is rather unusual, the fauna of the east and west Pacific normally being distinct. The G1 of Asian P. crassipes appears to have never been figured or compared with the American P. crassipes. The examination of the G1 of Japanese specimens (NSMT Cr7516, Cr 6822) shows them to be very similar to the American P. crassipes. Despite this, preliminary DNA analyses by C. Schubart (pers. comm.) indicate genetic differences between the Asian and American populations and, if these are confirmed by additional data (morphology, larval development, colour pattern), the two could be considered separate species.
description: Published as part of 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, pp. 1-66 in Zootaxa 1015 (1) on pages 9-12, DOI: 10.11646/zootaxa.1015.1.1, http://zenodo.org/record/5049232