Abstract
A total of 545 specimens belonging to the genus Krithe were obtained from 45 surface sediment samples collected from Suruga Bay, the Pacific side of central Japan. These specimens were classified into three species on the basis of differences in carapace morphology, which can be clearly traced in each species to the young larval stage (A-6). The three species were identified as K. sawanensis Hanai, 1959, K. antisawanensis Ishizaki, 1966 and K. surugensis Zhou and Ikeya n. sp. Each species has a distinct depth range and distributional area in Suruga Bay. Krithe sawanensis is distributed throughout the entire bay at depths of 120-1, 350 m. In contrast, the distribution of K. antisawanensis is restricted to the vicinity of the bay mouth, and K. surugensis is limited to the eastern area of the central trough. These two species are distributed at depths between approximately 150-650 m. The difference in distribution pattern and the intraspecific variation of the three species is correlated with environmental parameters such as water depth, water temperature, and dissolved oxygen. Two populations of K. sawanensis having distinct carapace size and vestibule shape were recognized. The populations are separated from each other by an ostracode-barren zone (OBZ) at depths of about 650-810m.
