Pachygrapsus minutus A. Milne­Edwards, 1873

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 : 31-34

Pachygrapsus minutus A. Milne­Edwards, 1873 ( Figures 9a–d , 14c , 15c )

Pachygrapsus minutus A. Milne­Edwards, 1873a: 292 , pl. 14, fig. 2 [type locality: New Caledonia]. — Cano, 1889: 240 (Hawaiian Is.). — Alcock, 1900: 399 (Mergui Archipelago). — Rathbun, 1906: 840 (Hawaiian Is.); 1907: 30 (Tuamotu Archip.; Caroline Is.); 1911: 242 ( Seychelles). — Tesch, 1918: 77 (Celebes; synonymy). — Balss, 1934a: 229 (Christmas I.; synonymy). — Boone, 1934: 180, pl. 91 ( Samoa). — Tweedie, 1936: 46 (Christmas I.); 1950a: 94 ( Malaysia). — Schmitt, 1939: 22 ( Clipperton). — Holthuis, 1953: 31 ( Kiribati); 1977: 158 (Red Sea). — Hertlein & Emerson, 1957: 5 ( Clipperton). —Edmonson, 1959: 171 ( Fiji, Samoa, Line Is., Hawaiian Is.). — Forest & Guinot, 1961: 155 (Society Is., Tuamotu Archip.). — Crosnier, 1965: 26, fig. 23, 29–30 ( Madagascar). — Garth, 1965: 27, fig. 14 ( Clipperton); 1992: 4 (Revillagigedo Is.). — Chace, 1966: 644, fig. 11e (Caroline Is.; synonymy). — Sakai, 1976: 635, fig. 347a–c ( Japan). — Monteforte, 1984: 172, annex 1, tab. a (Society Is., Tuamotu Archip.); 1987: 9 (Society Is.). — Peyrot­Clausade, 1985: 462 (Society Is.); 1989: 113 (Tuamotu Archip.). — Dai & Yang, 1991: 510 ( China sea). — Ng et al., 2001: 41 ( Taiwan; references). — Davie, 2002: 218 (Christmas I., Ashmore and Cartier Is., Middleton and Elizabeth reefs). — Ng & Davie, 2002: 379 ( Thailand). — Paulay et al., 2003: 495 (Mariana Is.). — Yeo et al., 2004: 88 (Anambas Is., South China Sea).

Sesarma murrayi Calman, 1909: 708 (Christmas I.).

Pachygrapsus murrayi — Ward, 1934: 25 (Christmas I.).

Type material

Five males syntypes, 5.9 x 8.0–7.6 x 10.4 mm, poor condition ( MNHN B3582 ). Male 7.6 x 10.4 mm is herein designated as lectotype, the remaining four specimens as paralectotypes .

Material Examined

New Caledonia: Types specimens, coll. M. Balansa, 5 M 5.9 x 8.0–7.6 x 10.4 mm (poor condition) (dry collection, MNHN B3582 ) .

Caroline Is. Palau: landward from Ngchesau reef, supra­tidal karst, exposure on top of reef, coll. G. Paulay, 7 March 2003, 1 ov. F 7.2 x 10.3 mm ( UF 3882 ) . — Yap: Maap I., high intertidal, under rocks and plant debris, coll. G. Paulay, 1 April 2000, 1 M 3.6 x 5.1 mm ( UF 8000 ) .

Mariana Is. Saipan: Garapan pier, reef flat, under rocks 1 m, coll. J. Stammer, 15 November 1997, 1 M 6.6 x 9.4 mm, 4 F 5.2 x 7.4–6.1 x 8.7 mm ( UF 590 ) . — Guam: 13°26.74’N, 144°39.54’E, Apra Harbor on mooring buoy 16, 0–10 m, coll. G. Paulay, 23 August 2000, 1 M 6.4 x 8.7 mm ( UF 3173 ) ; Tagachang reef flat, intertidal, under rocks, coll. G. Paulay, 6 July 1997, 2 M 4.4 x 6.3, 5.9 x 8.5 mm ( UF 123 ) .

Niue: Alofi, Utuko reef flat, exposed on reef surface, coll. B. Holthuis & G. Paulay, 13 September 1991, 1 M 3.5 x 5.4 mm ( UF 2246 ), 1 F 4.4 x 6.6 mm ( UF 2250 ) .

French Polynesia. Gambier Is.: Aukena I., intertidal, RV Marara campaign, coll. J. Poupin, April 1995, 1 ov. F 5.7 x 8.0 mm MNHN (B29270) . — Society Is.: Tahiti , intertidal, RV Marara campaign, coll. J. Poupin, November 1995, 1 M 4.2 x 5.4 mm ( MNHN B29271) . — Marquesas Is.: Nuku Hiva I., Taiohae Bay , intertidal, RV Marara campaign, coll. J. Poupin, 9 February 1996, 1 ov. F 3.2 x 5.0 mm ( MNHN B29272) . — Tuamotu Archip.: Moruroa Atoll , lagoon, intertidal in rubbles, RV Marara campaign, coll. J. Poupin, October 1995, 8 M 4.0 x 5.6–5.2 x 7.0 mm, 6 ov. F 3.3 x 4.7–5.7 x 8.0 mm, 5 F 3.3 x 4.8–4.9 x 7.0 mm ( MNHN B29273) .

Clipperton Atoll. Among rocks at low tide, Jean­Louis Etienne Expedition to Clipperton, coll. J. Poupin, February 2005, 13 M 4.0 x 5.5–7.5 x 9.0 mm, 1 ov. F 4.0 x 5.0 mm, 8 F 3.5 x 5.0–8.0 x 10.0 mm ( MNHN B29860) .

Diagnosis

Small­size species. Carapace subtriangular, lateral margins strongly convergent posteriorly with no tooth behind external orbital angle ( Fig. 9a ). Dorsal surface weakly convex with faint transverse striae on protogastric, hepatic, branchial regions; striae without setae or only few; mesogastric region smooth or with few striae; cardiac, intestinal regions smooth. Front 0.5 times width at exorbital angles; anterior margin sinuous ( Fig. 9b ). Infraorbital margin minutely dentate over entire length, separated from exorbital tooth by very low indentation ( Fig. 14c ).

Chelipeds equal. Outer faces of chelae regularly convex, with faint longitudinal stria near lower margins, extending to fixed finger; tip of fingers spoon­like, without setae ( Fig. 9c ). Dorsal margins of P2–P4 carpi, propodi with scattered long setae; woolly tomentum on P2 carpi, propodi of females, juveniles. Lower margin of P5 merus with 1–2 submedian tubercles and 2 spines of unequal size at distal angle ( Fig. 9d ).

Abdominal tergites smooth; sixth somite of abdomen plus telson triangular in male ( Fig. 9e ). G1 rounded at tip with short gutter­like process at tip, vertically oriented ( Fig. 15c ).

Colour (from Clipperton specimens): carapace and legs with large and irregular patches of brown on a white to cream background. The brown patches form more or less transverse bands on the segments of the ambulatory legs.

Measurements: small size; carapace usually about 5 x 7 mm; carapace of specimens examined ranging from: males 3.5 x 5.4–6.6 x 9.4 mm; females 3.3 x 4.4–7.2 x 10.3 mm; smallest ovigerous female is 3.2 x 5.0 mm.

Distribution

Indo­West Pacific from Red Sea to Mexican oceanic islands: Madagascar, Thailand, Indonesia, Australia, China, Japan, west and east Pacific islands (Caroline Is., Mari­

ana Is., Fiji, Niue, Kiribati, Samoa, Hawaiian Is., Line Is., French Polynesia, Clipperton, Revillagigedo Is.).

Habitat Rocks and rubble in the intertidal zone.

Remarks

Pachygrapsus minutus is conspicuous by its small size. It is morphologically close to the similar­sized P. planifrons De Man, 1888 , but the two can be easily separated. The front is straighter in P. planifrons ( Fig. 9b , 10b ) than in P. minutus , the tips of the cheliped fingers are furnished with setae in P. planifrons but are absent in P. minutus ( Fig. 9c , 10c ), the submedian tubercle on the lower margin of the P5 merus is absent in P. planifrons ( Fig. 9d , 10d ), and the G1 has a rounded tip with a short vertical gutter­like process in P. minutus ( Fig. 15c ) instead of a petal­like tip in P. planifrons ( Fig. 15d ). Pachygrapsus minutus is also morphologically close to P. propinquus De Man, 1908 . The similarities between the two are discussed under P. propinquus .

Figures

FIGURE 9. —Pachygrapsus minutus A. Milne­Edwards, 1873. Male 4.3 x 5.9 mm Moruroa, French Polynesia (MNHN B29273): a) dorsal view; b) front; c) right chela, outer face; d) right P5; e) abdomen.

FIGURE 10. —Pachygrapsus planifrons de Man, 1888. Male 7.0 x 9.0 mm, Rangiroa, French Polynesia (UF 1490): a) dorsal view; b) front; c) left chela, outer face; d) right P2; e) right P5; f) abdomen.

FIGURE 14. —Infra–orbital margin: a) Pachygrapsus fakaravensis Rathbun (1907), ov. female 15.0 x 16.5 mm, Taiaro, French Polynesia (MNHN B25782); b) Pachygrapsus laevimanus Stimpson, 1858, neotype male 18.0 x 21.7 mm, Sydney, Australia (AM P7478); c) Pachygrapsus minutus A. Milne­Edwards, 1873, male 5.2 x 7.0 mm, Moruroa, French Polynesia (MNHN B29273); d) Pachygrapsus planifrons de Man, 1888, male 7.0 x 9.0 mm, Rangiroa, French Polynesia (UF 1490); e) Pachygrapsus plicatus (H. Milne Edwards, 1837), male 12.1 x 15.3 mm, Taiaro, French Polynesia (MNHN B29279); f) Pachygrapsus corrugatus (von Martens, 1872) ov. female 13.6 x 15.2 mm, Virgin Is. (USNM 72340); g) Pachygrapsus crassipes Randall, 1840, male 31.9 x 36.6 mm, Sagami Bay, Japan (NSMT Cr7516); h) Pachygrapsus gracilis (de Saussure, 1858), ov. female 8.5 x 11 mm, Angola (MNHN B12903); i) Pachygrapsus loveridgei Chace, 1966, male 8.1 x 10 mm, St. Helena I. (MNHN B17836); j) Pachygrapsus marmoratus (Fabricius, 1787), female 12.7 x 14.3 mm, Préfailles, France (MNHN B22654); k) Pachygrapsus maurus (Lucas, 1846), female 12.7 x 14.3 mm, Banyuls, France (MNHN B12933); l) Pachygrapsus transversus (Gibbes, 1850), male 17.0 x 22.5 mm, French Guiana (MNHN B16013). Scale bar 1 mm.

FIGURE 15. —Male gonopods: a) Pachygrapsus fakaravensis Rathbun (1907), holotype 18.0 x 19.4 mm, Fakarava, French Polynesia (USNM 32844), right G1, abdominal face (left) and detail of terminal portion, sternal face (right); b) Pachygrapsus laevimanus Stimpson, 1858, neotype 18.0 x 21.7 mm, Sydney, Australia (AM P7478), left G1, abdominal (left) and sternal face (right), setae omitted; c) Pachygrapsus minutus A. Milne­Edwards, 1873, cl 8.2 mm, Caroline Is., lateral (left) and abdominal face (right), setae omitted; d) Pachygrapsus planifrons de Man, 1888, 9.5 x 11.8 mm, Hawaiian Is. (USNM 29350), right G1, abdominal (left) and sternal face (right); e) Pachygrapsus plicatus (H. Milne Edwards, 1837), cl 11.7 mm, Hawaiian Is., lateral (left) and abdominal face (right); f) Pachygrapsus corrugatus (von Martens, 1872), cl 8.5 mm, Ascension I., left G1 abdominal face (left) and detail of terminal portion, setae omitted (right); g) Pachygrapsus crassipes Randall, 1840, cl 35.6 mm, California, lateral (left) and abdominal face (right) setae omitted; h) Pachygrapsus gracilis (de Saussure, 1858), cl 8.7 mm, Virgin Is., lateral (left) and abdominal face (right), setae omitted; i) Pachygrapsus loveridgei Chace, 1966, holotype 10.3 x 13.1 mm, St. Helena I. (USNM 112457), left G1, abdominal (left) and sternal face (right); j) Pachygrapsus marmoratus (Fabricius, 1787), cl 30.5 mm, Gibraltar, lateral (left) and abdominal face (right), setae omitted; k) Pachygrapsus maurus (Lucas, 1846), cl 8.5 mm, Canary Is., lateral (left) and abdominal face (right) setae omitted; l) Pachygrapsus transversus (Gibbes, 1850), cl 11.1 mm, Key West, Florida, lateral (left) and abdominal face (right), setae omitted. (c, e, g–l, from Chace, 1966, fig. 10–11; f, from Manning & Chace, 1990, fig. 43). Approximate magnification x 6 (x 12 for detail of terminal portion).