ULTRASTRUCTURE OF THE SPERMATOZOON OF AVITELLINA-CENTRIPUNCTATA (CESTODA, CYCLOPHYLLIDEA), A PARASITE OF THE SMALL-INTESTINE OF CATTLE IN SENEGAL

The Avitellina centripunctata spermatozoon is filiform, tapered at bot h ends and lacks mitochondria. The anterior extremity exhibits an apic al cone and a crested-like body 150-200 nm thick. The axoneme is surro unded by a fine layer of lucent cytoplasm and a sheath of electron-den se material. The cytoplasm is slightly electron-dense at the anterior tip of the apical cone and in region IV of the spermatozoon. Over the rest of the gamete it is subdivided into numerous electron-lucent comp artments by irregularly spaced walls. The nucleus is electron-dense. I t interposes itself between the cortical microtubules which are all el ectron-dense centred and spiralized along their whole length. An apica l zone containing spiralized microtubules, cortical microtubules which are all electron-dense centred and stop before reaching the posterior extremity of the nucleus, as well as the subdivision into cavities by intracytoplasmic proteinaceous material, have never been described be fore in a cestod. Moreover, the crested-like body of Avitellina centri punctata is the thickest of those which have been described to date in the cestods.