Hermit crabs of the genus Calcinus Dana, 1851 (Decapoda: Anomura: Diogenidae) from the Austral Islands, French Polynesia, with description of a new species

Knowledge of morphology, coloration, and distribution of species of Calcinus Dana, 1851 from French Polynesia is expanded based primarily on collections obtained during the French BENTHAUS Expedition in 2002 to the Austral Islands, the southernmost of the French Polynesian islands. Six species of Calcinus were obtained from inshore to depths of 280 m. Of these, one proved to be a new species, C. albengai, and is fully described. This new species has two colour variants, one with pale pink to cream chelipeds that lives in shallow-water from the intertidal to about 50 m, the other with bright orange chelipeds, from deeper waters from about 50 to 280 m. Morphologically this new species is distinguished by differences in the armature of the ocular acitcles, aspects of the left and right palms, ventrodistal pilosity of third pereopods, and telson armature. Five species were collected by dredging, trawling, or using traps, in depths of 40 to 280 m: C. anani Poupin & McLaughlin, 1998, C. gouti Poupin, 1997, C. haigae Wooster, 1984, C. spicatus Forest, 1951, and C. aff. sirius Morgan, 1991. Of these, C. gouti was previously known exclusively based on the holotype from Tuamotu, and a more complete diagnosis is presented; the others are also diagnosed, including new details on coloration. Inshore and scuba collecting on Rapa Island produced four additional, but better known species: C. elegans (H. Milne Edwards, 1836), C. latens (Randall, 1840), C. laevimanus (Randall, 1840), and C. vachoni Forest, 1958. The inshore Calcinus fauna of Rapa is briefly compared with its counterpart on Easter Island, located at the same latitude 3500 km to the east. A total of 19 (or possibly 20, should C. sirius be confirmed in the future) Calcinus species are now known from French Polynesia. Cases of sibling species of Calcinus, distinguished almost exclusively by coloration, are summarized

本研究依托2002年法国BENTHAUS探险队于法属波利尼西亚最南端的奥斯特群岛（Austral Islands）采集的标本，拓展了对细螯寄居蟹属（Calcinus Dana, 1851）物种的形态学特征、体色模式与分布范围的认知。本次采集共获取6种细螯寄居蟹，采样生境覆盖近岸至280米水深区间。其中1种为新物种——C. albengai，本文对其进行了全面的形态描述。该新种存在两种体色变型：一种的螯足呈淡粉色至乳白色，栖息于潮间带至约50米的浅水环境；另一种的螯足呈亮橙色，栖息于约50至280米的深水区域。该新种的形态鉴别特征包括眼棘（ocular acicles）的纹饰结构、左右掌节的形态差异、第三步足腹远端的刚毛分布，以及尾节的棘突特征。另有5种细螯寄居蟹通过拖网、耙网或诱捕装置，在40至280米水深中采集得到，分别为：C. anani Poupin & McLaughlin, 1998、C. gouti Poupin, 1997、C. haigae Wooster, 1984、C. spicatus Forest, 1951，以及C. aff. sirius Morgan, 1991。其中C. gouti此前仅基于土阿莫土群岛的正模标本被记录，本文为其提供了更为完整的鉴别诊断；其余4个物种亦完成形态鉴别，并补充了体色相关的新细节。在拉帕岛（Rapa Island）的近岸区域与水肺潜水采样中，还获取了另外4种认知程度更高的已知物种：C. elegans (H. Milne Edwards, 1836)、C. latens (Randall, 1840)、C. laevimanus (Randall, 1840)，以及C. vachoni Forest, 1958。本研究还将拉帕岛的近岸细螯寄居蟹物种区系，与位于其东侧3500公里、纬度相近的复活节岛（Easter Island）的同类区系进行了简要对比。目前法属波利尼西亚境内已知的细螯寄居蟹物种共计19种——若未来确认C. sirius的分布，则该数量可增至20种。本文最后总结了几乎仅通过体色即可区分的细螯寄居蟹姊妹种案例。