A Monogenean Parasite Gyrodactylus masu sp. n. (Monogenea: Gyrodactylidae) of Salmonid Fish in Japan

Abstract

Description and identification is made of Gyrodactylus masu sp. n. collected from fins, body surface, gill filaments and gill arches of cultured salmonid fish (Oncorhynchus masou, O. rhodurus and Salmo gairdneri) in Japan. The new species is most similar to G. derjavini Mikailov, 1975 in the shape of the hard parts, but different from it in the size of the hamuli and marginal hooks. Monthly monitoring of G. masu sp. n. on a single stock of Oncorhynchus masou was made during the period of May 1978 to Sep. 1979. There was a slight tendency that the hamuli and marginal hooks increased in length with decreasing water temperature and vice versa. © 1986, The Japanese Society of Fisheries Science. All rights reserved.