Abstract
Hinuma (36°16'N, 140°30'E) is a small brackish water lake situated in the Kanto District, central Japan. A survey of the bottom fauna of the lake was carried out in April 1963. As the result, 23 species of macro benthic animals were collected (Table 2). Two species of polychaete worms, one species of crab and one species of isopod crustacea were added to the fauna by the supplementary collection in the littoral zone of the lake. Except for one fresh water component, Tubificidae sp., all are brackish or euryhaline species of marine origin. One species of cumacean crustacea seems to be new to science, and a small brackish polychaete, Prinospio japonica, is recorded for the first time the Pacific coast of Japan. The benthic communities are as follows ; I. Reed marsh ; Assiminea japonica-Neanthes diversicolor community, II. Coastal shallow zone ; Corbicula japonica-Neanthes diversicolor community, III. Flat bottom of the main part ; Prionospio japonicus community, a. Western part ; Tubiflcidae sp. present, b. Central part ; Benthos is poor both in quality and quantity, c. Eastern part ; Tubificidae sp. absent. Benthic communities of Lake Hinuma are compared with that of the brackish lakes in Japan, and it is pointed out that the Prionospio japonicus community in Lake Hinuma is a unique one.
