Light and electron microscopic studies on Epieimeria anguillae (Léger & Hollande, 1922), a coccidium parasitizing the European eel, Anguilla anguilla L.

Abstract. The foregut of eels naturally infected by Epieimeria anguillae (Léger & Hollande, 1922) was studied by light and electron microscopy. It has been established that this parasite, which develops in a characteristic location on the surface of epithelial cells, and was classified on this basis by Dyková & Lom (1981) as a member of the genus Epieimeria , undergoes intracellular merogony and gamogony similarly to other eimerians; however, its sporogony takes place outside the fish or intercellularly. The trophozoites and merogonic and gamogonic stages each develop in a para-sitophorous vacuole which is half embedded in the epithelial cell and protrudes into the intestinal lumen. The parasitophorous vacuote is surrounded by a single membrane; however, towards the intestinal lumen it is covered also by the cell membrane. In its location, Epieimeria anguillae resembles cryptosporidia, but differs from the latter significantly in its relationship with the host cell.