Ultrastructure of the spermatozoon ofHymenolepis straminea(Cyclophyllidea, Hymenolepididae), intestinal parasite ofArvicanthis niloticus(Rodentia) in Senegal

Abstract

Summary The mature H. straminea spermatozoon is filiform and lacks mitochondria. It exhibits an apical cone of electron-dense material and eight helicoidal crest-like bodies 50–100 nm in thickness. The cortical microtubules are spiralized and make an angle of about 30° to the spermatozoon axis. The axoneme, of the 9+“1” pattern of the Platyhelminthes, does not reach the extremities of the spermatozoon. The nucleus is a compact cord wound in a spiral around the axoneme. Depending on the level of section it appears annular or crescent-shaped. The cytoplasm exhibits many electron-dense granules in regions III, IV and V of the gamete. A nucleus with both annular and crescent-shaped sections has never been described in a species of the Hymenolepididae. In addition we report for the first time the existence of eight crest-like bodies of different length in the cestodes.