Studies on the Morphology and Biology of Acetodextra amiuri (Stafford) (Trematoda: Heterophyidae)

Abstract

Acetodextra amiuri is a heterophyid trematode which parasitizes fishes, especially Siluridae. A. amiuri is of unusual interest in several respects. In structure it is typical of the Heterophyidae and yet it is a parasite of fishes, whereas other members of that family, as restricted by Price (1940), occur in birds and mammals. This situation is further evidence that closely related trematocdes may not necessarily occur in related hosts, although the type of host has been stressed in taxonomy by some investigators. A. amiuri is unusual also in respect to its localization in the definitive host. All other adult trematoces in the superfamily Opisthorchioidea live in the digestive tract or its appended organs whereas A. amiuri does not. While this trematode was knowni for some time only from the air bladder of catfishes, it is evident from the present study that the ovaries are the more important site. This trematode may be histozoic or even cytozoic, as young worms were observed within the eggs of the host. This unusual site of infection in the definitive host is not only unique in the Opisthorchioidea but has been reported for no other adult digenetic trematode. Thus A. amiuri presents a number of problems differing from those encountered in the investigation of any other member of its family. Among these problems are 1) the method by which the definitive host becomes infected, 2) the effects on reproduction of the host, 3) the fate of the parasite in males of the definitive host species, and 4) the means whereby the eggs of the parasites escape to continue the life cycle.