First occurrence of ophiuroid-parasitic genus Ophieulima (Mollusca: Gastropoda: Eulimidae) in the North Pacific Ocean

Abstract

A eulimid gastropod of the genus Ophieulima, parasitic on the disc of the ophiactid brittle star Ophiactis dyscrita, was collected from 256–343 m deep off Kanagawa, central Japan. This represents the first record of the genus from Japanese waters and even from the North Pacific Ocean. Here we describe it as Ophieulima yoshiharai n. sp. The generic assignment is justified by its conchological characters including (1) a small, conical shape with convex teleoconch whorls, (2) many fine growth lines and some strong growth pause scars on the teleoconch, (3) a well-developed, twisted columella, and (4) a multispiral, brownish transparent protoconch. Ophieulima yoshiharai n. sp. is distinguishable from the three (two named and one undescribed) extant, as well as two fossil congeners by its slender shell with the length of 2.1 times larger than width, a small aperture and a protoconch of 3.5 whorls. The new species is also characterized by its bathymetric distribution, which is shallower than the extant species of Ophieulima. On the other hand, the hosts of Ophieulima species are so far restricted to ophiuroids of the genus Ophiactis and the three named species have mostly been found attached to the lateral and/or dorsal sides of the host's disc, suggesting their similar parasitic ecology.