2001 Volume 36 Issue 2 Pages 47-55
Pike eels Muraenesox cinereus (41-116 cm in total length; n=23) purchased from fish markets in Aichi Prefecture were infected with the digenetic trematode Aerobiotrema muraenesocis in the swim bladder (11 out of 23 fish; intensity of infection 1-27). Effects of the infection on the host were studied and partial life history of this trematode was postulated. Eggs of the trematode were spherical or sub-spherical. They could hatch in the water with a wide range of salinity (1/3 to undiluted). Hatched larvae had an unusual appearance, with long cilia limited on the antero-lateral sides of their body. Histochemical staining revealed that the trematode sucks blood from the swim bladder of the host. Moreover, severe histopathological changes were observed in the tunica interna of the swim bladder, including deep and irregular undulations of the epithelium, marked thickening of the tunica propria and hemorrhaging ulcers within the tunica interna. In case where these pathological changes had proceeded, the intimate association of the epithelium with the capillaries in the tunica propria was severely disturbed. According to these histopathological observations, it appears that heavy infection with this trematode may cause lowered functions of the host's swim bladder.