Key words: Philophthalmidae, Philophthalmus rhionica, miracidium, ultrastructure
The study of ultrastructure of Philophthalmus rhionica miracidium was carried out. Up to date, the ultrastructures of miracidium have been studied in a restricted number of species belonging to the families Notocotylidae, Paramphistomatidae, Sanguinicolidae, Fasciolidae, and Schistosomatidae (Galaktionov, Dobrovol'sky, 1998). The ultrastructure in representatives of two latter families, Fasciola hepatica and Schistosoma mansoni respectively, have been examined most carefully. The family Philophthalmidae differs from the families Fasciolidae and Schistosomatidae by the aberrant pedogenetic miracidium.