Description and first occurrence of Myxidium zealandicum (Protozoa: Myxosporidia) in the North American eel Anguilla rostrata LeSueur

Abstract

Myxidium zealandicum Hine, 1975 is described from gills and kidney of the North American eel Anguilla rostrata collected from the St. Lawrence River near Quebec City and Cornwall. Cysts of M. zealandicum on gills measured up to 1 by 2 mm and in kidneys up to 15 by 20 mm. In addition to single spherical cysts, several polymorphous forms were also observed on the gills. Polymorphous cysts were not found in the kidney. Different stages of spore development were evident in gill cysts and were differentiated by means of a lead hematoxylin – fast green stain. Number and pattern of spore striations were examined by scanning electron microscopy and were highly variable. The invasion of the parasite into kidney tissue appeared to result in less physiological damage to the host than did gill invasion. The existence of this parasite, previously found in eel species in New Zealand, in a North American eel species is discussed.