Pachygrapsus plicatus (H. Milne Edwards, 1837 )

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 : 37-42

Pachygrapsus plicatus (H. Milne Edwards, 1837) ( Figures 11a–f , 14e , 15e )

Grapsus plicatus H. Milne Edwards, 1837: 89 [type locality: Hawaiian Is.]. — Krauss, 1843: 43, pl. 3, fig. 1 (Natal).

Goniograpsus plicatus — Dana, 1852: 343 (Hawaiian Is.).

Goniograpsus kraussii Dana, 1852: 343 ( South Africa, Natal; new synonymy, see remarks).

Grapsus kraussii —H. Milne Edwards, 1853: 170 (Natal; see remarks).

Pachygrapsus striatus A. Milne­Edwards, 1873b: 82 ( Samoa, Hawaiian Is.; new synonymy, see remarks).

Pachygrapsus kraussii — Stebbing, 1910: 319 (Natal).

Pachygrapsus natalensis Ward, 1934: 25 (Christmas I.). — Tweedie, 1936: 46 (Christmas I., same as Ward).

Pachygrapsus spec. Holthuis, 1953: 32 (Tuamotu Archip.; see remarks).

Pachygrapsus plicatus — Stimpson, 1858: 48 [102] (Ryukyu Is.); 1907: 117 (Ryukyu Is.). —A. Milne­Edwards, 1873a: 292, pl. 15, fig. 1 ( New Caledonia). — Kingsley, 1880: 200 (Society Is.; Hawaiian Is.). — Richters, 1880: 140 ( Mauritius). — Ortmann, 1894: 708 ( Samoa; synonymy). — Rathbun, 1906: 839 (Hawaiian Is.); 1907: 29 ( Micronesia, Tuvalu, Tuamotu Archip.); 1911: 241 ( Seychelles; Chagos Archipelago). — Tesch, 1918: 77 ( Indonesia; synonymy). — Balss, 1934b: 524 (Réunion). — Tweedie, 1947: 32 (Christmas I.; synonymy); 1950b: 130 (Cocos­Keeling Is.). — Barnard, 1950: 117, fig. 22b, 24b (KwaZulu­Natal). — Holthuis, 1953: 32 (Marshall Is., Tuamotu Archip.). —Edmonson, 1959: 171, fig. 10a (Hawaiian Is.). — Forest & Guinot, 1961: 154 (Tuamotu Archip.). — Crosnier, 1965: 27 (Glorieuses Is.). — Chace, 1966: 644, fig. 11g (Hawaiian Is.). — Sakai, 1976: 636, pl. 218, fig. 2 (Ogasawara Is., Japan). — Monteforte, 1984: 172, annex 1, tab. a (Society Is., Tuamotu Archip.); 1987: 9 (Society Is.). — Dai & Yang, 1991: 512 (Xisha or Paracel Is.). — Poupin, 1994: 63, fig. 59, pl. 7f (Tuamotu Archip.). — Fransen et al., 1997: 126 ( Indonesia). — Ng et al., 2001: 41 ( Taiwan; references). — Davie, 2002: 218 (Catalogue). — Paulay et al., 2003: 495 (Mariana Is.).

Type material

Two female syntypes (12.0 x 16.5, 15.0 x 19.0 mm) in poor condition ( MNHN B3585 ). The largest female is here designated as the lectotype, the second female the paralectotype .

Material Examined

Hawaiian Is.: Types specimens, coll. M. Freycinet, 2 F 12.0 x 16.5, 15.0 x 19.0 mm (dry collection MNHN B3585 ; poor condition). Honolulu , Waikiki marine lab., leg. From Smithsonian U.S. Fish Commission, under rock near shore, coll. ‘T. H.’, 2 January 1942, 1 M 11.8 x 15.0 mm ( MNHN B24497). Labelled as “ Pachygrapsus striatus M. Edw., Iles Sandwich ”, coll. M. Baillien, 3 M 13.0 x 13.0–14.0 x 16.0 mm (dry collection MNHN B3586 ; see remarks) .

La Réunion: “ Ruisseau de Saint­Benoit ,” leg. G. Petit, 1 M 11.4 x 14.8 mm ( MNHN B12896) .

Marshall Is. Arno Atoll: from boulders and rocks, high on the sea reef boulder rampart, coll. R. W. Hiatt, June–September 1950, 1 F 6.6 x 8.6 mm ( UNSM 95009).

Mariana Is. Saipan: Garapan pier, reef flat, under rocks, 1 m, coll. J. Stammer, 15 November 1997, 1 F ov. 10.4 x 12.9 mm, 4 F 5.2 x 7.4–6.1 x 8.7 mm ( UF 584 ) . Guam, Tarague reef flat, coll. T. Rongo, 1 June 1997, 1 M 12.6 x 15.4 mm ( UF 130 ) ; “Tumon moat” on buoy, coll. G. Paulay, 8 May 1999, 1 M 7.6 x 10.0 mm ( UF 138 ) .

New Caledonia: “Collection A. M. Edw.” 1 M 9.0 x 11.5 mm (poor condition), 1 M 16.0 x 18.0 mm, 1 F 15.2 x 18.6 mm (poor condition) (dry collection MNHN B3584).

Western Samoa. Upolu I.: “Godeffroy Mus., 1888”, 1 M 11.7 x 15.0 mm, 1 ov. F 8.5 x 11.1 mm, MZS (dry collection Cru 1210); 1 F 10.3 x 13.5 mm (dry collection MNHN B3583).

Niue: North Alofi , catholic mission, within 5 meters of cliff face or beach inland side of reef flat, exposed rocks surfaces 0–10 cm, coll. Holthuis & Paulay, 30 September 1991, 1 M 2.7 x 3.5 mm ( UF 2256 ) .

French Polynesia. Austral Is.: Raevavae I., intertidal, RV Marara campaign, coll. J. Poupin, 16 March 1995, 1 M juv. 4.3 x 5.7 mm, 1 ov. F 9.6 x 12.7 mm, 3 F juv. 5.0 x 6.3– 6.3 x 8.2 mm ( MNHN B29274) . — Marquesas Is.: Nuku Hiva I., intertidal, RV Marara campaign, coll. J. Poupin, probably 1996, 1 M 10.7 x 13.5 mm, 1 F 7.8 x 10.8 mm, 1 F juv. 4.5 x 6.2 mm ( MNHN B29275) . — Society Is.: Huahine I., “Fare” harbour, among rocks, RV Marara campaign, coll. J. Poupin, 1 M 15.1 x 18.5 mm ( MNHN B29277) . — Tahiti , intertidal, RV Marara campaign, coll. J. Poupin, November 1995, 1 M juv. 3.7 x 5.0 mm ( MNHN B29276) . — Tuamotu Archip.: Makemo Atoll , coll. RV Albatross, 24 October 1899, 1 M 5.8 x 8.2 mm ( USNM 33180 ) . — Moruroa Atoll , RV Marara campaign, coll. J. Poupin, October 1995, 5 M 6.5 x 8.9–9.4 x 12.3 mm, 1 ov. F 15.0 x 19.3 mm, 2 F 6.4 x 9.1, 7.0 x 9.3 mm ( MNHN B29278) . — Rangiroa Atoll, Avatoru Motu, ca. at 1.5 km E of Post Office, at Pension Henri , reef flat, under rocks, 0–1 m, coll. G. Paulay, 10 January 2001, 1 M 8.2 x 10.7 mm, 1 ov. F 7.7 x 9.9 mm ( UF 1491 ) . — Raroia Atoll: Takoke Motu , under stones about high tide line, or little below, coll. J. P. E. Morrison, 21 July 1952, 1 F juv. 5.2 x 7.0 mm ( USNM 95110 ) ; Ngarumaoa Motu , from outer reef plate, coll. J. P. E. Morrison, 11 July 1952, 1 M (broken) 11.5 x 14.0 mm, 1 ov. F 8.4 x 11.4 mm, 1 juv. 3.9 x 5.6 mm ( USNM 95010 ) ; Oneroa Motu , from low tide line or just above (wet area) on large reef block at night, coll. J. P. E. Morrison, 5 August 1952, 2 M 12.8 x 15.8, 15.4 x 18.8 mm, 3 ov. F 10.2 x 12.6–14.8 x 18.5 mm, 1 F 11.7 x 15.0 mm ( USNM 94883 ) . — Taiaro Atoll, intertidal, outer reef, Taiaro Expedition , coll. J. Poupin, 12–20 February 1994, 3 M 6.0 x 7.9 mm –12.1 x 15.3 mm, 1 ov. F 7.8 x 10.7 mm ( MNHN B29279) .

Diagnosis

Dorsal surface of carapace convex; entirely covered with coarse transverse striae, each furnished with setae, including cardiac, intestinal regions; lateral margins weakly convergent posteriorly, with no tooth behind exorbital angle ( Fig. 11a ). Front 0.5 times width at exorbital angles; anterior margin sinuous ( Fig. 11b ). Infraorbital margin markedly dentate over entire length, with deep outer notch ( Fig. 14e ).

Merus of cheliped with transverse striae furnished with setae; inner distoventral lobe with 3–4 teeth. Carpus with numerous short striae furnished with setae; inner dorsodistal spine broad at base, distally curved. Outer face of chela regularly convex; lower half with 3–4 main longitudinal striae, without setae, and few additional short oblique striae, near lower margin; upper half tuberculated ( Fig. 11c ). Cutting edges of fingers with several triangular teeth of unequal size, as illustrated on figure 11c; tip of fingers smooth and spoonlike.

Meri of ambulatory legs with transverse striae furnished with setae on outer faces, distoventral angles with 2–3 spines; carpi, propodi with few scattered long bristles on upper margin; P2 propodi with anterodorsal brush of setae, sometimes indistinct on larger males; lower margin of P5 merus without submedian tubercle ( Fig. 11d–e ).

Abdominal tergites smooth; sixth somite of abdomen plus telson triangular in male ( Fig. 11f ). Distal process of G1 slender with two large lobes at tip ( Fig. 15e ).

Colour: carapace white to cream with a pattern of irregular brown patches on carapace as illustrated on figure 11a. Chelipeds with brown to violet hues on meri and carpi, chelae almost totally white to light yellow. Ambulatory legs white to brown, with irregular median bands on meri, carpi and propodi; dactyli brown, paler at base.

Measurements: medium size; carapace of specimens examined ranging from 2.7 x 3.5 mm to 15.1 x 18.5 mm, for males, and 4.5 x 6.2 mm to 15.0 x 19.3 mm, for females; smallest ovigerous female is 8.5 x 11.1 mm.

Distribution

Indo­West Pacific from east Africa to Tuamotu Archip.: East Africa; Glorieuses Is.; Seychelles; La Réunion; Mauritius; Christmas I.; Cocos­Keeling Is.; Indonesia (Java); South China Sea (Xisha or Paracel Is.); Taiwan; Japan; Mariana Is. (Saipan); Micronesia (Kosrae); Marshall Is. (Arno); New Caledonia; Samoa; Niue, Tuvalu; Hawaiian Is.; French Polynesia (Austral Is., Marquesas Is., Tuamotu Archip., Society Is).

Habitat Intertidal, on reef flat and under rocks; common and easily collected at night.

Remarks

Pachygrapsus plicatus is morphologically close to P. corrugatus (von Martens, 1872) , from the west and central Atlantic, and to P. fakaravensis Rathbun, 1907 , from the west and central Pacific. The three species have in common the carapace shape, which is coarsely striated transversally, and the presence of longitudinal striae on the outer face of the chelae. Pachygrapsus plicatus differs from these two species by the lateral margins of its carapace, weakly convergent posteriorly instead of being subparallel, the absence of setae on the striae of the carapace and of the outer face of the chelae, smooth abdominal tergites and different G1, petal­like tip in P. plicatus ( Fig. 15e ) and acicular in P. corrugatus and P. fakaravensis ( Fig. 15a, f ).

Krauss (1843: pl. 3, fig. 1, 1a–c) showed a female crab from Natal, South Africa, that he attributed to Grapsus plicatus H. Milne Edwards, 1837 , which was described from the Hawaiian Is. Although Krauss’ figure is of good quality, it seems that the artist exaggerated the spines on the upper and lower margin of the P5 merus. It was this character that led Dana (1852: 343) to believe it was a new species, Goniograpsus kraussii , commenting that “from the dentations on the third joint of the posterior legs of Krauss’s species on both margins, we judge that his species must be a different one”. Dana’s identification was followed by H. Milne Edwards (1853: 170, as Grapsus kraussii ), and by Stebbing (1910: 319, as Pachygrapsus kraussii ). All other characters described and figured by Krauss (1843) clearly belong to P. plicatus , especially the form of the outer face of the chelae. Furthermore, P. plicatus was later recorded from Natal by Barnard (1950), who included an illustration of the characteristic G1. Pachygrapsus kraussii ( Dana, 1852) is therefore here formally considered a junior synonym of P. plicatus (H. Milne Edwards, 1837) .

Ortmann (1894: 708) and Tesch (1918: 77) considered P. striatus A. Milne­Edwards, 1873 , a junior synonym of P. plicatus , which was confirmed by the examination of the three male syntypes of P. striatus ( MNHN B3586). These specimens undoubtedly belong to P. plicatus and should not be confused with P. fakaravensis . Their carapace is coarsely striated, with lateral margins weakly convergent posteriorly, the outer face of the chelae has three main longitudinal striae without setae, and the abdominal tergites are smooth and without striae. It is not clear why A. Milne­Edwards (1873: 82) alluded to “ Grapsus striatus Milne Edwards ”. All earlier work of both H. Milne Edwards and A. Milne­Edwards was examined without finding a reference to this species, so it is assumed that he referred to an unpublished manuscript.

The small specimen from Raroia Atoll that Holthuis (1953: 32) attributed to Pachygrapsus spec. , (juvenile female, USNM 95110) is clearly identifiable as P. plicatus . It had the brush of setae on the P2 merus that is usually present in small specimens of P. plicatus , although it tends to disappear on larger specimens, particularly males.

Figures

FIGURE 11. —Pachygrapsus plicatus (H. Milne Edwards, 1837). Male 12.1 x 15.3 mm, Taiaro, French Polynesia (MNHN B29279): 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).