Pachygrapsus planifrons De Man 1888
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 planifrons

description: Pachygrapsus planifrons De Man, 1888 (Figures 10a–f, 14d, 15d)   
 Pachygrapsus planifrons De Man, 1888: 368, pl. 16, fig. 2 [type locality: Noordwachter Island = Jaga Utara, Java Sea off Java, Indonesia, 05°12'S, 106°27'E]. — De Man, 1908: 218 (remarks on P. longipes status). — Tesch, 1918: 77 (Indonesia; synonymy). — Ward, 1934: 25 (Christmas I.). — Tweedie, 1936: 45 (Christmas I.); 1950b: 130 (Cocos­Keeling Is.). — Holthuis, 1953: 31 (Kiribati; Tuamotu Archip.). —Edmonson, 1959: 173, fig. 10b (Hawaiian Is.; synonymy). — Garth, 1965: 30, fig. 15–16 (Clipperton). — Chace, 1966: 644, fig. 11f (Hawaiian Is.; synonymy). — Chen, 1980: 139: fig. 22, pl. IV­3 (Paracel Is.). — Dai & Yang, 1991: 510, fig. 261 (Hainan). — Ng & Davie, 2002: 379 (Thailand). — Paulay et al., 2003: 495 (Guam). — Komai et al., 2004: 34 (Japan). — Yeo et al., 2004: 88 (Anambas Is., South China Sea).   
 Pachygrapsus longipes Rathbun, 1893: 247 (Hawaiian Is.). — Rathbun, 1906: 840 (Hawaiian Is.); 1907: 30 (Fakarava Atoll, Tuamotu Archip.); 1911: 242 (Seychelles).   
 Pachygrapsus laevis Borradaile, 1900: 592, pl. 42, fig. 7 (Tuvalu; new synonymy see remarks). — Tesch, 1918: 76 (Key).   
 Type material   
Presumably lost. According to C. H. Fransen (pers. comm.) the syntypes were probably deposited at Göttingen (ZMG), but are not found there (G. Tröster, pers. comm.), nor are they part of the material that was transferred from Göttingen to Frankfurt (SMF). The Göttingen collection was in poor condition before being transferred to Frankfurt, and a number of types of other species also appear to have been lost (M. Türkay, pers. comm.).  
 Material Examined   
 Mariana Is. Guam: Bile Bay, supratidal/intertidal, among rocks, common, coll. G. Paulay, 29 March 1998, 2 M 5.1 x 6.3, 5.6 x 6.8 mm (UF 129).   
 Caroline Is. Yap: Maap I., high intertidal, under rocks and plants debris, coll. G. Paulay, 1 April 2000, 1 ov. F 5.2 x 6.7 mm (UF 3849; Photo GP805).   
 Tuvalu. Funafuti: coll. J. S. Gardiner, 1 ov. F 5.1 x 7.2 mm (UMZC Reg. 11.01.1897; holotype of Pachygrapsus laevis Borradaile, 1900).   
 French Polynesia. Tuamotu Archip.: Fakarava Atoll, coll. RV Albatross, 12 October 1899, 1 F 3.6 x 4.9 mm (USNM 33179). — Rangiroa Atoll, Avatoru Motu, ca. at 1.5 km E of Post Office, at Pension Henri, reef flat, under rocks, 0–1 meter, coll. G. Paulay, 10 January 2001, 1 M 7.0 x 9.0 mm, 2 ov. F 5.4 x 7.0–5.6 x 7.3 mm (UF 1490). — Taiaro Atoll, Taiaro Expedition, intertidal, outer reef, 12–20 February 1994, coll. J. Poupin, 1 ov. F 4.6 x 6.0 mm (MNHN B29264).   
 Hawaiian Is.: Honolulu, coll. RV Albatross, 1891, 1 ov. F 6.2 x 8.2 mm (USNM 17320, type of P. longipes Rathbun, 1893); Honolulu reef, coll. RV Albatross, 6 June 1902, 1 M 9.5 x 11.8 mm (UNSM 29350).   
 Clipperton Atoll. Among rocks at low tide, Jean­Louis Etienne Expedition to Clipperton, coll. J. Poupin, February 2005, 6 M 5.5 x 7.0–9.7 x 11.5 mm, 10 ov. F 4.0 x 6.5–9.5 x 12.0 mm, 1 F 4.5 x 5.5 mm (MNHN B29859); reef at low tide, stn 33, coll. L. Albenga, J. M. Bouchard, 25 January 2005, 5 M 6.0 x 7.0–7.0 x 8.5 mm, 1 ov. F 6.5 x 8.0 mm, 1 F 4.5 x 5.5 mm (MNHN B29858).   
 Diagnosis   
Small­size species. Carapace with concave lateral margins, markedly convergent posteriorly, without tooth behind exorbital angle (Fig. 10a). Dorsal surface flattened, only weakly convex; protogastric, hepatic regions with thin transverse striae, branchial region with oblique striae; all striae glabrous; mesogastric, cardiac, intestinal regions almost totally smooth. Front 0.6 times width at exorbital angles, anterior margin almost straight (Fig. 10b). Infraorbital margin nearly entire, composed of low granules, outer indentation very low; infraorbital margin forming very obtuse angle with inner margin of exorbital tooth (Fig. 14d).  
Cheliped merus with 4–5 acute spines at inner distoventral angle. Carpus with sharp inner dorsodistal spine. Outer face of chelae regularly convex; fixed finger with a longitudinal stria extending slightly on outer face of chela; cutting edge with 2–3 large teeth medially and few smaller teeth proximally. Dactyl with 6–8 small teeth over whole length of cutting edge, sometimes indistinct. Tip of fingers spoon­like, with distinctive rows of bristles (Fig. 10c).  
Ambulatory legs with scattered long bristles on carpi, propodi, dactyli, but without brush of setae. Upper margins of meri armed with several long mobile spines, lower margins with 1–2 spines (usually 2) at distoventral angles; lower margin of P5 merus smooth, without submedian tubercle (Fig. 10d–e).  
Abdominal tergites smooth. Telson of male rounded at tip, longer than sixth somite; telson and sixth somite forming triangle with lateral margins slightly concave (Fig. 10f). G1 slender, petal­like at tip (Fig. 15d; see remarks).  
Colour (from Clipperton specimens): brown overall, with darker transverse bands on the ambulatory legs: proximal, median and distal bands on meri (sometimes unclear); proximal and distal bands on carpi and propodi; and median band of variable width on dactyli. Eggs orange red.  
Measurements: small size; usual carapace size 5 x 7 mm; greatest size indicated in the literature 9 x 11 mm (Edmondson, 1959; Garth, 1965); specimens examined ranged from: males 5.1 x 6.3–5.6 x 6.8 mm, females 4.6 x 6.0–5.6 x 7.3 mm; smallest ovigerous female 4.6 x 6.0 mm.  
 Distribution   
 West Indian Ocean to east Pacific islands: Seychelles; Christmas I,, Cocos­Keeling Is.; Thailand, Indonesia; South China Sea (Anambas Is., Hainan I., Xisha or Paracel Is); Japan; Caroline Is.; Mariana Is.; Kiribati; Funafuti; Hawaiian Is.; Tuamotu Archip.; Clipperton.   
 Habitat Common in the high intertidal zone, under rocks and debris.   
 Remarks   
 Pachygrapsus planifrons is unique in possessing rows of bristles at the tips of the fingers of the chelae. This character alone is sufficient to distinguish it from all other species of Pachygrapsus. It is similar to P. minutus in its small size, but the two can be easily separated. The exorbital angle is produced and more spinous in P. planifrons than in P. minutus, the lateral margins of the carapace are concave in P. planifrons but straight in P. minutus, the anterior margin of the front is almost straight in P. planifrons but sinuous in P. minutus, the lower margin of the P5 merus is smooth in P. planifrons while having a submedian tubercle in P. minutus and the distal end of the G1 has a short vertical gutter­like process in P. minutus (Fig. 15c) but a petal­like tip in P. planifrons (Fig. 15d).   
 Chace (1966: 645) indicated that Pachygrapsus was in need of revision and figured the gonopods of 8 species in the USNM collection. These figures have been very useful for the present study and some of them are reproduced in Figure 15. Some inconsistencies were found with the figure of the G1 of P. planifrons (Chace, 1966: 645, fig. 11f, a male cl 9.5 mm from Honolulu), however. It has a gutter­like tip instead of tulip­like as shown in Figure 15d, even if the G1 illustrated here is from the same specimen as that of Chace, as its size and collection details were the same, and the G1 was already dissected in the jar. We therefore assume that there was a mistake made when Chace’s plate was being prepared. The tulip­like shape of the P. planifrons G1 was also found in other males examined here, as well as in one illustrated for a Chinese specimen (Chen, 1980: 140, fig. 22­5).   
 Borradaile (1900: 592, pl. 42, fig. 7) described P. laevis from a female collected at Funafuti. The characters described by Borradaile are those of P. planifrons, especially the characteristic rows of bristles at the tips of the fingers of the chelae. The type of P. laevis (UMZC 11.01.1897) was examined and it can be confirmed that it is a junior synonym of P. planifrons.
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 34-37, DOI: 10.11646/zootaxa.1015.1.1, http://zenodo.org/record/5049232