Calcinus gouti Poupin 1997

Calcinus gouti Poupin, 1997 (Figs. 1 c, 3)

Calcinus gouti Poupin, 1997: 690, figs. 3B, 5F, 7A (type locality: Moruroa Atoll, Tuamotu, French Polynesia); Poupin, 1998: 38; Poupin & McLaughlin, 1998: 13 (French Polynesia).

Type material. Holotype: Tuamotu, Moruroa Atoll, coll. B. Gout, 7.x.1996, ov. Ψ 2.6 mm (MNHN Pg 5412).

Material examined. French Polynesia: Tuamotu, Rangiroa Atoll: off Motu Maeherehonae, outer reef slope, under rocks, 6–12 m, 10.xi.2001, coll. G. Paulay: 1 ɗ 5.0 mm, 1 ov. Ψ 4.0 mm, 1 (damaged) + uncounted no. in shells (UF 1863). Tikehau Atoll: outer end of Passe Tuheiava, outer reef slope, under rocks, 15 m, 10.vii.2001, coll. G. Paulay: 1 ɗ 5.0 mm (UF 1349). Society, Moorea Island: East of Passe Taotoi, outer reef slope, under rocks, 12–25 m, 22.x.2001, coll. G. Paulay: 1 spec. in shell of Astralium confragosa (UF 1849). Austral Islands, BENTHAUS Expedition: Thiers Bank: stn DW 1926, 24°38.16’S, 146°00.82’W, 50–90 m, 13.xi.2002: 1 Ψ 2.9 mm (MNHN Pg 6392). Arago Bank: stn DW 1968, 23°22.88’S, 150°43.52’W, 100–120 m, 20.xi.2002: 1 ov. Ψ 3 mm, 1 Ψ 2 mm (MNHN Pg 6393); stn DW 1977, 23°22.32’S, 150°43.5’W, 90–95 m, 21.xi.2002: 1 ɗ 4.5mm (MNHN Pg 6391).

Diagnosis. Ocular acicles (Fig. 3 a) with 2–4 terminal spines. Left chela (Fig. 3 b) with 6–8 spines on upper margin; outer face of palm regularly convex. Upper margin of right chela (Fig. 3 c) with 5 or 6 corneous­tipped spines. Dactyl of P3 subequal in length to propodus or slightly shorter; distal pilosity of P3 more pronounced than on P2, more dense in larger specimens (Figs. 3 d–e) but not quite forming brush of setae. Posterior lobes of telson (Fig. 3 f) with 5–9 spines terminally, and 4–9 spines laterally, on left lobe; and 3–7 spines terminally, and 1 or 2 spines laterally, on right lobe. Shield cream on proximal half, turning to brown on distal half; with 2 dark brown patches on anterior half. Ocular peduncles pink, grading to white or pale blue on distal 0.3. Antennular peduncles yellow with pale blue on distal 0.25 of terminal segments; flagella yellow. Antennal peduncles and antennal acicles pale brown to yellow, with white­tipped spines; flagella yellow. Chelipeds brown fading to white or pale blue on distal half of chelae and fingers; meri each with dorsodistal dark brown patch extending on lateral and mesial faces; carpi each with similar patch on dorsoproximal area; outer and inner faces of chelae (Fig. 3 b, c) each with submedian dark brown spot. Ambulatory legs (Figs 3 d­e) with coxae, meri and carpi almost totally pink with white or pale blue near articulations; propodi and dactyls pink with narrow white bands proximally and distally. Abdomen white to cream.

Distribution. Known only from French Polynesia. Depth: 10 to 120 m.

Habitat. Coral bottoms, sometimes associated with Pocillopora.

Remarks. Juveniles of Calcinus species often have the upper margin of the left chela armed with spines that disappear with growth in adult males. However, in large males of C. gouti, spines are still present on the upper margin (Fig. 3 b).

The coloration of C. gouti was described by Poupin (1997, figs. 3B, 5F) based exclusively on the holotype, a female specimen of small size (2.6 mm, MNHN Pg 5412), and differs slightly from the specimens examined during this study. In the holotype, the shield is cream, lacking brown patches. On P2 and P3, the pink bands on carpus, propodus and dactyl are short, the pink band on the merus is restricted to the upper half of the segment; and there are weakly defined light yellow stripes on the lateral faces of merus, carpus, propodus and dactyl. However, these differences have been found to be related to growth. With increasing size, the brown patches on the shield become more clear, the pink bands on the segments of P2 and P3 become wider, and the yellow stripes disappear.

Calcinus gouti is similar to C. pulcher and C. lineapropodus Morgan & Forest, 1991. The three have similar coloration on the ocular peduncles, a submedian dark spot on the outer and inner faces of the chelae, and similarly armed ocular acicles and telson. They can be separated by the colour pattern of the ambulatory legs, which have stripes in C. lineapropodus (see Morgan & Forest 1991, fig. 2e), or bands and longitudinally arranged flecks in C. pulcher (see Poupin 1997, fig. 3B; Asakura & Nomura 2001, fig. 3A,E), instead of only bands as in C. gouti. They also differ in ventrodistal pilosity of P3, which is weak and similar to that of P 2 in C. pulcher and C. lineapropodus, whereas in C. gouti pilosity is more pronounced on P3 than on P2.

Calcinus gouti is also similar to C. hakahau Poupin & McLaughlin, 1997, from the Marquesas Islands, in coloration of ocular peduncles and ambulatory legs, and armature of ocular acicles and telson. These two differ only by the presence in C. gouti, or absence in C. hakahau, of a submedian spot on the outer and inner faces of the chelae. Poupin & McLaughlin (1998) indicated that ventrodistal pilosity of P 3 in C. hakahau is weak, similar to that of P2, and they used this as one of the characters to separate the two species.

However, examination of previously unreported specimens of C. hakahau from the Marquesas (Ua Huka, 6–15 m, MNHN Pg 6351–6353) showed that at least in larger specimens the ventrodistal pilosity of P3 is more pronounced than on P2, and is similar to that observed in C. gouti. Thus, it appears that currently C. gouti and C. hakahau can be reliably distinguished only using differences in coloration. The former also has a wide distribution in French Polynesia, whereas the latter is known only from the Marquesas Islands.