Taxonomy and Ecology of Two New Interstitial Cytheroid Ostracoda (Crustacea) from Shimoda, Central Japan

Abstract

Two new interstitial cytheroid ostracods are described from a small sandy beach in Shimoda, central Japan: Microloxoconcha ikeyai sp. nov. (Cythero- matidae) and Parvocythere japonica sp. nov. (Parvocytheridae). This is the first record of the genus Parvocythere Hartman, 1959 from Japan. By sam- pling every two months through a year along a transect extending from the shoreline landward across the study area, the optimal zone for each species was found. The peaks of individual density for M. ikeyai and P. japonica lie seaward and landward, respectively. Both species show a wide tolerance to changes in salinity, but they do not live where fine sand (mode of grain size less than 1/8mm) is the dominant particle size. In assays of phototaxis, M. ikeyai, which has a naupliar eye, showed negative phototaxis.