Two new species of non-marine Ostracoda (Crustacea) of the genera Vestalenula Rossetti amp; Martens, 1998 (Darwinuloidea) and Microloxoconcha Hartmann, 1954 (Cytheroidea) from Tsushima, Japan, and a summary of the non-marine ostracod fauna of the island.

Abstract

The archipelago of Tsushima is located in the Korea Strait, at the southern end of the Sea of Japan (East Sea), and lies almost equidistant from Korea and Japan. Its non-marine ostracod fauna was previously unknown, although potentially of (palaeo-) zoogeographical interest considering its position. Preliminary surveys of freshwater and brackish habitats on the island in August/September and November/December 2019, revealed a total of 31 species in five families and three superfamilies. Two species are described as new. Vestalenula gravata sp. nov. is a small representative of the family Darwinulidae, characterized by a very long keel on the right valve and the absence of a pigmented eye. This species was found in very shallow streams with poorly sorted substrates in forests. Microloxoconcha semicircularis sp. nov., an interstitial Cytheroidea, was recovered from the tidal part of a small river, the first time this genus has been found in this type of habitat. Two other undescribed species are figured, but left in open nomenclature due to insufficient number of individuals: Vestalenula sp. and Cobanocythere sp. The antennule and antenna of Vestalenula sp. are most similar to those of three species from Brazil.