Two strigeoid trematodes, Apatemon (Apatemon) gracilis (Rudolphi, 1819) and Diploetomum (Dolichorchis)galaxiae n. sp., which encyst in the freshwater fish Galaxias auratus Johnston in Lake Crescent, Tasmania.

Abstract

The metacercaria and adult of Apatemon (Apatemon) gracilis (Rudolphi) and Diplostomum (Dolichorchis) galaxiae n.sp. are described and figured. Metacercarial cysts of these species occur in different parts of the endemic fish Galaxias auratus: A. gracilis in the body cavity, orbit and vitreous humour, and D. galaxiae n.sp. visible as black spots ('black-spot disease') in the musculature of the body and head. A gracilis which has not previously been recorded from Australia occurs in the black duck, Anas superciliosa, while D. galaxiae n.sp. infects the white-faced heron, Ardea novaehollandiae. The domestic duck, Anas platyrhynchos, is much more susceptible to experimental infection by Apatemon gracilis than by D. galaxiae n.sp. Both flukes inhabit the upper small intestine of their bird hosts. The reproductive system of D. galaxiae n.sp. is amphitypic. D. galaxiae n.sp. most closely resembles D. heronei Srivastava, 1954 and D. ketupanensis Vidyarthi, 1937; a key to species in the sub-genus Dolichorchis is given.