THE ULTRASTRUCTURE OF THE ONCOSPHERAL ENVELOPES OF FIMBRIARIA-CZAPLINSKII GRYTNER-ZIECINA, 1994 (CESTODA, HYMENOLEPIDIDAE)

The envelopes of oncospheres of a hymenolepidid tapeworm with an aquat ic life cycle Fimbriaria czaplinskii, surrounding larvae inside the gr avid part of the strobila, were examined under a transmission electron microscope. Details of the ultrastructure of the outer envelope and t he inner envelope with its two derivatives: the embryophore and oncosp heral membrane are described. The ultrastructural features of F. czapl inskii envelopes are compared and discussed with those described previ ously in the other hymenolepidids, and particularly with the related s pecies Fimbrial-ia fasciolaris.