Pachygrapsus propinquus De Man, 1908

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 : 42-44

Pachygrapsus propinquus De Man, 1908 ( Figure 12 a­c)

Pachygrapsus propinquus De Man, 1908: 216 , pl. 18, fig. 2 [type locality: Port Canning, near Calcutta, India]. — Tesch, 1918: 76 (Key).

Type material

Unknown. The types are neither in RMNH (C. Fransen, pers. comm.) nor SMF (M. Türkay, pers. comm.), nor BMNH (P. Clark, pers. comm.), nor ZMA (first author unable to locate it, June 2005). Probably in the Zoological Survey of India, Calcutta .

Diagnosis (adapted from De Man, 1908)

Carapace 0.75 times longer than wide; lateral margins weakly convergent posteriorly, with no tooth behind exorbital angle ( Fig. 12a ). Dorsal surface slightly convex with distinct cervical groove; hepatic and branchial regions with glabrous striae; mesogastric, cardiac and intestinal regions smooth. Front about 0.5 times exorbital width, anterior margin sinuous. Infraorbital margin with 3–4 small obtuse teeth, uneven on inner part; outer notch low.

Left chela unknown. Outer face of right chela very finely granular, slightly convex, with conspicuous longitudinal line running from tip of fixed finger to near carpal articulation ( Fig. 12b ); upper margin with finely granular oblique ridges. Tip of fingers spoonlike, glabrous.

Ambulatory legs slender with few scattered long bristles on carpi, propodi, dactyli. Meri with transverse ridges on their outer faces; lower margin of P5 merus without submedian tubercle, distoventral angle with 2 spines.

Abdominal tergites smooth. Sixth somite of abdomen plus telson triangular in male. G1 unknown.

Colour (from De Man, 1908: 218): “slate­coloured upper surface of the carapace, and the red­brown legs are mottled with small dark spots.”

Measurements (from De Man, 1908; only two specimens): probably a small­size species (see remarks); carapace 6.25 x 8.3 mm (male), 8.0 x 10.7 mm (female).

Distribution Indian Ocean. Port Canning, near Calcutta, India.

Habitat Intertidal, brackish water pools.

Remarks

De Man (1908) compared his two specimens of P. propinquus with one male of P. minutus . These two species appear to be closely related, and De Man listed as many similarities as differences. The differences he mentioned, such as “chela less convex” or “ambulatory legs slenderer”, are relative and thus difficult to evaluate. With only two specimens of P. propinquus known, it is difficult to see the extent of morphological variation, or to know what size the species may attain. Additional specimens from the type locality must be studied before a proper comparison with P. minutus can be made. The shape of the G 1 in P. propinquus is unknown. Based on De Man’s description, the following characters can be used to separate the two species: the lateral margins of the carapace are weakly convergent posteriorly in P. propinquus but strongly convergent in P. minutus , the lower margin of the P5 merus is smooth in P. propinquus but with 1–2 submedian tubercles in P. minutus .

Figures

FIGURE 12. —Pachygrapsus propinquus de Man, 1908. a) dorsal view; b) right chela, outer face; c) abdomen; a, b, female 8.0 x 10.7 mm, c, male 6.25 x 8.3 mm, Port Canning, India (from de Man, 1908, pl. 18 fig. 2).