Pseudorhadinorhynchus samegaiensis (Acanthocephala: Echinorhynchida: Illiosentidae) Uses the Amphipod Jesogammarus (Annanogammarus) fluvialis as an Intermediate Host in a Stream of the Lake Biwa Basin, Central Japan

摘要

Cystacanths and acanthellae of the illiosentid acanthocephalan Pseudorhadinorhynchus samegaiensis Nakajima and Egusa, 1975 are described from the anisogammarid amphipod Jesogammarus (Annanogammarus) fluvialis Morino, 1985 in a stream at the Samegai Trout Experimental Station, the type locality of the acanthocephalan, in the Lake Biwa basin, Shiga Prefecture, west-central Japan. This amphipod is herein regarded as an intermediate host of P. samegaiensis. This is the first description of developmental stages of any member of the genus Pseudorhadinorhynchus Achmerov and Dombrovskaja-Achmerova, 1941. Since J. (A.) fluvialis does not occur in the Lake Biwa proper but two other congeners, J. (A.) annandalei (Tattersall, 1922) and J. (A.) naritai Morino, 1985,inhabit the lake, it is suggested that P. samegaiensis uses one or both of the latter two amphipods as its intermediate host(s) in the lake.