ULTRASTRUCTURE OF SPERMIOGENESIS AND THE SPERMATOZOON OF VAMPIROLEPIS-MICROSTOMA (CESTODA, HYMENOLEPIDIDAE), INTESTINAL PARASITE OF RATTUS-RATTUS

Spermiogenesis in Vampirolepis micrastoma begins with the formation of a nuclear cone and a differentiation zone. This is delimited at the f ront by arched membranes, bordered by cortical microtubules, and conta ins two parallel centrioles linked together at their bases by electron -dense, amorphous material. The nuclear cone elongates, becomes filifo rm, and migrates into the spermatid body. Later, one of the centrioles gives rise to a flagellum that grows at the same pace as the cortical microtubules. Subsequently, 6 crested bodies form and the old spermat id separates from the residual cytoplasm, The mature V. microstoma spe rmatozoon is filiform and lacks mitochondria. Its anterior end exhibit s six crested bodies 100 to 200 nm thick of unequal lengths. The axone me is of the 9+''1'' pattern. The cortical microtubules are spiralized and make an angle of about 20 to 30 degrees to the spermatozoon axis, except at their posterior extremity where they become parallel to thi s axis. The nucleus is an electron-dense cord coiled in a spiral aroun d the axoneme. The cytoplasm is slightly dense but contains many elect ron-dense granules in regions III, IV, and V of the spermatozoon. The presence of centrioles linked together at their bases by electron-dens e material has never, to our knowledge, been reported in a Platyhelmin th. Likewise, a nuclear migration, right from the beginning to the end of spermiogenesis, has never been described in a cestode. In addition , we observe fur the first time the existence of six crested bodies in a cestode from a Mammal. Microsc. Res. Tech. 42:218-225, 1998. (C) 19 98 Wiley-Liss, Inc.