First Record of the Parasitic Ciliate Trichodina truttae Mueller, 1937 on Chum Salmon Fry (Oncorhynchus keta) from Japan.

Abstract

The parasitic ciliate Trichodina truttae Mueller, 1937 is redescribed from silver-impregnated specimens collected from the body surface of chum salmon fry (Oncorhynchus keta) reared in five hatcheries of Hokkaido and northern Honshu, Japan. The description is supplemented by scanning electron microscopic observations. The distinguishing morphological features include its large size (body diameter 115-178 .mu.m), high number (10-23) of radial pins per denticle, and the presence of two markedly different lengths of cilia within the adoral ciliary spiral. Geographical variation was observed in the body size and number of denticles. This is the first record of T. truttae from Japan.