Calcinus albengai, Poupin, Joseph & Lemaitre, Rafael, 2003

Poupin, Joseph & Lemaitre, Rafael, 2003, Hermit crabs of the genus Calcinus Dana, 1851 (Decapoda: Anomura: Diogenidae) from the Austral Islands, French Polynesia, with description of a new species, Zootaxa 391, pp. 1-20 : 3-7

Calcinus albengai n. sp. ( Figs 1 a,b, 2, 5a)

Type material. French Polynesia, Austral Islands, BENTHAUS Expedition. Marotiri Isles, Holotype, stn DW 1888, 27°51.38’S, 143°31.42’W, 100–120 m, 6.xi.2002: 1 ɗ 3.8 mm, ( MNHN Pg 6359). Thiers Bank, Paratypes, stn DW 1927, 24°39.03’S, 146°01.58’W, 95–105 m, 13.xi.2002: 1 ɗ 4.0 mm (parasitized by bopyrid isopod Parathelges weberi Nierstrasz & Brender à Brandis, 1923), 1 juv. ( MNHN Pg 6360); Neilson Reef, stn DW 1914, 27°03.52’S, 146°04.01’W, 150 m, 11.xi.2002: 4 ɗ 2.2–5.0 mm, 1 ov. Ψ 3.0 mm, 4 juv. in shells ( MNHN Pg 6361).

Other material. French Polynesia, Austral Islands, BENTHAUS Expedition. Macdonald Bank: stn DW 1877, 28°59.012’S, 140°15.102’W, 59–150 m, 4.xi.2002: 1 juv. ( MNHN Pg 6362). Marotiri Isles: stn DW 1879, 27°54.8’S, 143°30.14’W, 52 m, 6.xi.2002: 1 ɗ 1.8 mm, 1 Ψ 1.8 mm ( MNHN Pg 6379); stn DW 1880, 27°54.8’S, 143°29.45’W, 90–94 m, 6.xi.2002: 3 ɗ 2.2–2.6 mm, 15 juv. in shells ( MNHN Pg 6363); stn DW 1881, 27°54.6’S, 143°28.5’W, 112–121 m, 6.xi.2002: 1 ɗ 2.6 mm ( MNHN Pg 6364); stn DW 1888, 27°51.38’S, 143°31.42’W, 100–120 m, 6.xi.2002: 1 Ψ 1.9 mm, 10 juv. ( MNHN Pg 6365). Off Rapa Island, NE bank: stn CP1906, 27°24.78’S, 144°01.75’W, 110–127 m, 9.xi.2002: 1 ov. Ψ 2.0 mm ( MNHN Pg 6366). Rapa Island: Komire Point, malacologist team, dive 10, 16– 18 m, 7.xi.2002: 1 ɗ (damaged) ~ 2.2 mm, 1 ov. Ψ 2.6 mm ( MNHN Pg 6380); Komire Point, NE, malacologist team, stn 26, 27°33.0’S, 144°19.1’W, living coral, 53 m, 14.xi.2002: 1 ɗ 3.5 mm ( MNHN Pg 6382); N of Anatakuri Bay, malacologist team, stn 38, 27°37.4’S, 144°18.4’W, under stone, 2 m, 22.xi.2002: 1 Ψ 1.8 mm ( MNHN Pg 6383); Hiri bay, malacologist team, stn 9, 27°33.3’S, 144°22.2’W, coral, 3–24 m, 6.xi.2002: 1 Ψ 2.0 mm ( MNHN Pg 6384); W of Tauna Isle, malacologist team, stn 16, 27°36.3’S, 144°18.4’W, dead coral, 5 m, 9.xi.2002: 2 ɗ 1.3–1.9 mm ( MNHN Pg 6385); stn DW 1894, 27°40.13’S, 144°21.51’W, 100 m, 8.xi.2002: 1 juv. ( MNHN Pg 6367). Neilson Reef: stn CAS 1916, 27°00.3’S, 146°03.6’W, 180 m, 11.xi.2002: 1 ov. Ψ 3.4 mm ( MNHN Pg 6371); stn CP 1918, 27°03.45’S, 146°03.96’W, 130–140 m, 12.xi.2002: 6 ɗ 1.0– 2.6 mm, 3 ov. Ψ 1.9–2.3 mm, 1 Ψ 1.4 mm, 1 juv. ( MNHN Pg 6368); stn CP 1920, 27°03.58’S, 146°03.84’W, 120–203 m, 12.xi.2002: 2 juv. ( MNHN Pg 6369); stn CP 1922, 27°03.67’S, 146°03.93’W, 150–163 m, 12.xi.2002: 1 juv. in shell ( MNHN Pg 6370). Thiers Bank: stn DW 1926, 24°38.16’S, 146°00.82’W, 50–90 m, 13.xi.2002: 3 ɗ 1.0– 2.3 mm, 5 ov. Ψ 1.5–3.0 mm, 1 Ψ 2.0 mm ( MNHN Pg 6372), 1 ɗ 2.0 mm, 2 ov. Ψ 2.3–3.0 mm, 1 Ψ 1.6 mm ( MNHN Pg 6381); stn DW 1936, 24°39.71’S, 145°57.09’W, 80–100 m, 14.xi.2002: 1 ov. Ψ 2.5 mm, 1 juv. ( MNHN Pg 6373). Lotus Bank, off Raevavae Island: stn DW 1948, 23°48.7’S, 147°53.5’W, 120–280 m, 17.xi.2002: 1 ɗ 4.0 mm ( MNHN Pg 6374); stn DW 1946, 23°49.24’S, 147°41.25’W, 100– 200 m, 17.xi.2002: 1 ov. Ψ 1.6 mm, 1 Ψ 1.2 mm ( MNHN Pg 6375). Tubuai Island: stn DW 1958, 23°19.64’S, 149°30.3’W, 80–150 m, 18.xi.2002: 1 ɗ 2.1 mm ( MNHN Pg 6376). Arago Bank: stn DW 1978, 23°22.02’S, 150°43.41’W, 120–180 m, 21.xi.2002: 1 ɗ 1.8 mm ( MNHN Pg 6377); stn DW 1986, 23°26.3’S, 150°44.2’W, 150 m, 21.xi.2002: 1 Ψ 4.4 mm, 1 juv. in shell ( MNHN Pg 6378).

Diagnosis. Ocular acicle terminating in simple spine. Anterodorsal plate of branchiostegite with 1 or 2 spinules subproximally. Upper margin of right chela with 4 spines. Outer face of left chela regularly convex. Dactyl of P3 subequal in length to propodus or slightly shorter, with 6–8 small spines on ventral margin. Dactyls of P2 and P3 with similar setation consisting of sparse, widely­spaced tufts of setae. Propodus of P3 with dorsolateral margin evenly rounded. Telson with posterior lobes each with single terminal spine. Ocular peduncles bright orange with white suboblong or subcircular spots, and white distal band adjacent to corneas. Chelipeds bright orange except for white­tipped fingers, and small white suboblong or subcircular spots on outer face of dactyl and fixed finger. Ambulatory legs bright orange with white suboblong or subcircular spots.

Description. Shield about 0.9 times as long as broad. Rostrum ( Fig. 2 a) rounded, slightly overreaching level of broadly subtriangular lateral projections; anterior margins between rostrum and lateral projections concave. Anterodorsal plate of branchiostegite with dorsal margin nearly smooth, with few spinules on proximal half.

Ocular peduncles ( Fig. 2 a) 0.7–1.1 (average 0.9) times as long as shield, slightly constricted medially; peduncles each 3.5 to 6.5 times as long as diameter of cornea. Corneas weakly dilated. Ocular acicles well developed, subtriangular, terminating in simple spine. Antennular peduncles reaching to distal 0.25–0.3 of ocular peduncles. Ultimate segment 0.3–0.5 times as long as shield.

Antennal peduncles shorter than antennular peduncles, reaching between midpoint and distal 0.3 of ocular peduncles. First segment with ventrolateral angle produced, bearing 2 or 3 spines. Second segment with laterodistal angle produced, terminating in bifid spine; distomesial angle unarmed or with spine. Third segment with strong spine at ventrodistal angle. Fourth segment with dorsodistal spine. Fifth segment unarmed. Antennal acicle reaching beyond proximal margin of fifth antennal segment, terminating in strong spine; dorsolateral margin with spine distally, dorsomesial margin with row of 2–4 spines.

Left chela ( Fig. 2 b, g, 5a) 0.5–0.8 times as high as long. Dactyl equal or slightly longer than palm; cutting edge with 2 or 3 calcareous teeth; dorsolateral margin usually with row of granules. Fixed finger with 2 median teeth on cutting edge, and 1 or 2 smaller teeth proximally; outer and lower faces with low granules. Palm with outer face regularly convex, finely granular; lower face with some squamous tubercles; inner face smooth, with sharp ventral tubercle bearing few long setae; upper margin smooth ( Fig. 2 b) or with 7–11 spines ( Fig. 2 g). Carpus with prominent submedian tubercle on outer face; upper margin with 1 or 2 small spines or indentations, and strong spine at dorsodistal angle. Merus stout, triangular in cross­section; ventromesial margin with 2–4 spines distally; ventrolateral margin with 1 or 2 spines distally; upper margin unarmed.

Right chela ( Fig. 2 c) with 4 or 5 corneous spines on upper margin of palm. Dactyl about as long as palm; cutting edge with 2 triangular teeth; dorsal surface with 2 subparallel rows each of 3 or 4 spines. Fingers with some squamous tubercles basally; fixed finger with triangular tooth on cutting edge. Palm with outer face weakly convex, smooth; inner face flat, smooth. Upper margin of carpus with 2 or 3 spines increasing in size distally. Merus similar to that of left cheliped, often with spine on dorsodistal angle.

Ambulatory legs similar from left to right. P2 ( Fig. 2 d) exceeding left cheliped by length of dactyl when fully extended; dactyl 0.7–1.2 (average 0.9) times as long as propodus; ventral margin with widely­spaced, sparse tufts of setae and 6–8 minute spines; propodus with few long setae, and minute movable spine on ventrodistal angle; carpus 0.5– 0.7 times as long as propodus, with dorsodistal spine; merus about as long as propodus, with laterodistal spine. P3 ( Fig. 2 e) shorter than P2, overreaching tip of cheliped by distal half of dactyl when fully extended; ventrodistal pilosity similar to that of P2, not brushlike; dactyl 0.9–1.3 (average 1.0) times as long as propodus, ventral margin armed with 5– 9 minute spines; propodus with minute movable spine on ventrodistal angle, dorsolateral margin regularly rounded; carpus 0.6–0.8 times as long as propodus, with dorsodistal spine; merus about as long as propodus, with laterodistal spine sometimes small or indistinct.

Fourth pereopod semichelate. Dactyl terminating in corneous claw; ventrolateral margin with row of spinules. Propodus with broad rasp consisting of several rows of corneous scales. Carpus with dorsodistal spine. Merus unarmed; ventral margin with long setae. Fifth pereopod chelate, with rasp on propodus and dactyl. Carpus and merus unarmed, subovate in cross­section.

Abdomen with 4 unpaired biramous left pleopods in both sexes. Sixth abdominal tergite calcified, with dorsal face divided into 4 subequal areas by longitudinal and transverse furrows.

Telson ( Fig. 2 f) with posterior lobes asymmetrical, left more elongated than right; lobes with long setae marginally, and each with 1 posterior spine slightly curved ventrally.

Size. Male sl 1.0–5.0 mm; female sl 1.2–4.4 mm; ovigerous female sl 1.5–3.4 mm.

Live coloration. This new species has two colour variants, a deep­water variant in depths of about 50 to 280 m, and a shallow­water variant found at less than 50 m. The deep­water variant ( Fig. 1 a) has the following coloration. Shield bright orange to totally white. Ocular acicles, and ocular peduncles bright orange, the latter with white spots on dorsal and lateral surfaces, and white band adjacent to cornea ( Fig. 2 a). Antennular peduncles orange overall, with pale orange at articulation of segments; ultimate segment white on distal 0.2; flagella white to pale orange. Antennal peduncles orange overall; fifth segment with median longitudinal white stripe on dorsal surface; flagella pale orange. Antennal acicles bright orange with scattered white patches on dorsal surfaces. Chelipeds bright orange; fingers with white tips, and small subcircular to suboblong white spots on outer faces ( Figs. 2 b, c, g, 5a). Ambulatory legs bright orange with suboblong or sub­circular white spots on basis, coxae, meri, carpi, propodi and dactyls; terminal claws of dactyls black ( Fig. 2 d–e). Fifth and fourth pereopods with similar orange coloration but less bright, especially on fifth pereopod. Abdomen brown­orange; sixth abdominal tergite, uropods and telson with scattered orange patches.

The shallow­water colour variant ( Fig. 1 b) differs from the deep­water variant as follows. When it is not white, the shield is red­brown instead of bright orange. The ocular peduncles each have a white patch on the proximal 0.6 of the ventral surface, instead of being solid orange. The antennular peduncles are violet on distal 0.2 and flagella, instead of orange. The chelipeds are whitish­pink with some minute white orange spots at the finger tips. The ambulatory legs are red­brown with white spots larger and more elongated, arranged in straight lines ( Fig. 2 h).

Distribution. So far known only from the Austral Islands, French Polynesia, in the South central Pacific, between 23–29°S and 140–151°W. Depth: shore to 280 m.

Habitat. Calcinus albengai is the second Indo­West Pacific species of Calcinus with a depth range exceeding 150 m, the other being C. anani . This new species lives on coral substrates, and uses as housing gastropod shells of the families Bursidae (Bursa) , Cerithiidae (Cerithium) , Columbellidae (Mitrella) , Mithridae ( Cancilla ), Ranellidae (Gyrineum) , and Trochidae (Euchelus) .

Etymology. This new species is named for Laurent Albenga, assistant curator, Muséum national d'Histoire naturelle, Paris, in recognition of his invaluable, and dedicated assistance during the BENTHAUS Expedition.

Remarks. The armature of the left cheliped varies with growth and sex. The upper margin of the left chela is almost smooth in large males (sl 3 mm), or can be armed with 7 to 11 spines in smaller males (sl <3 mm) and all female sizes examined ( Figs. 2 b, g). A similar variation occurs on the outer face of the carpus where large individuals have a blunt submedian tubercle, and at most low spines on the upper margin; on the outer face of the carpus, small males and females have a strong spine with some smaller spines nearby, and 3 or 4 spines on the upper margin.

Coloration of the shield varies from fully coloured (bright orange or red­brown) to totally white. A somewhat similar observation for the shield is reported for C. anani by Poupin & McLaughlin (1998), and for C. gaimardii (H. Milne Edwards, 1848) by Asakura et al. (2002). Thus, it appears that shield coloration alone must be used with caution as a diagnostic character for Calcinus species.

Calcinus albengai is morphologically similar to C. dapsiles Morgan, 1991 , known from Western Australia at depths ranging from the subtidal to 97 m. These two species have similar armature of the ocular acicles and telson, aspects of the chelae, and ventrodistal pilosity of P3. However, they can be easily separated on the basis of live coloration. In C. dapsiles the ocular peduncles are brown, with a short, cream­coloured band adjoining the cornea; the chelipeds are brown fading to cream or white on the distal half of chelae and fingers; and the ambulatory legs are a mixture of white, pink, brown, and red. The colour pattern of the ambulatory legs of C. albengai bears some resemblance to that of C. anani , but the two are easily separated by coloration of the ocular peduncles (lacking spots in C. anani ), and ventrodistal pilosity of P3 (with brush­like setae in C. anani ).

The two colour variants of C. albengai have been found to be morphologically indistinguishable. Whether these variants could actually represent sibling species can not be ruled out. However, until in­depth studies (including DNA data) of additional specimens can be made there is no other practical alternative than to consider the material to represent a single species.

Figures

FIGURE 1. Live coloration (except b, taken several weeks after preservation): a, Calcinus albengai n. sp., deep­water variant, holotype ɗ 3.8 mm, Marotiri Isles, 100 – 120 m (MNHN Pg 6359); b, Calcinus albengai n. sp., shallow­water variant, ɗ 3.5 mm, Rapa Island, 53 m (MNHN Pg 6382); c, Calcinus gouti Poupin, 1997, ɗ 5.0 mm, Tikehau, 15 m (UF 1349); d, Calcinus aff. sirius Morgan, 1991, 1 ov. Ψ 5.5 mm, Rapa Island, 100 m (MNHN Pg 6395). Photographs by L. Albenga (a, b), G. Paulay (c), and J. Poupin (d).

FIGURE 2. Calcinus albengai n. sp.: a – f, holotype ɗ 3.8 mm, Marotiri Isles (MNHN Pg 6359); g, paratype ov. Ψ 3.0 mm, Neilson Reef, 150 m (MNHN Pg 6361); h, ɗ 3.5 mm, Rapa Island, 53 m (MNHN Pg 6382). a, anterior portion of shield and cephalic appendages; b, left chela and carpus, outer face; c, right chela and carpus, outer face; d, left P 2 of deep­water variant, outer face; e, left P 3 of deep­water variant, outer face; f, posterior portion of telson, ventral view; g, left chela and carpus, outer face; h, left P 3 of shallow­water variant, outer face. Scale bars 1 mm.