Elpidia soyoae, a new species of deep-sea holothurian (echinodermata) from the Japan Trench area

Abstract

A new species of holothurian, Elpidia soyoae sp. nov., is described from the Japan Trench area, at depths of 3570-4145 m. It is distinguished from its congeners in having: four or five paired papillae and unpaired papillae present along entire dorsal radii (four to seven papillae on each radius), with wide separation between second and third paired papillae; maximum length of Elpidia-type ossicles in dorsal body wall exceeds 1000 μm; axis diameter of dorsal Elpidia-type ossicles less than 40 μm; tentacle Elpidia-type ossicles with arched axis and shortened, occasionally completely reduced arms and apophyses. Purple pigmentation spots composed of small purple particles on both dorsal and ventral body wall. This is the second species of Elpidia Théel, 1876 from Japanese abyssal depths. The diagnosis of the genus Elpidia is modified to distinguish from all other elpidiid genera. A morphological comparison of the species of the slender axis group of genus Elpidia, and partial mitochondrial cytochrome c oxidase subunit I (COI) gene sequences of type specimens are provided.