Ultrastructure of spermiogenesis of Dipylidium caninum (Cestoda, Cyclophyllidea, Dipylidiidae), an intestinal parasite of Canis familiaris.

We describe for the first time the ultrastructure of spermiogenesis of a representative of the family Dipylidiidae, Dipylidium caninum. Spermiogenesis begins with the formation of a differentiation zone. This conical area presents two centrioles with associated striated roots. One of the centrioles develops a flagellum and posteriorly a proximodistal fusion is produced between the axoneme and a median cytoplasmic process. In a final stage of spermiogenesis a condensation of electron-dense material between cortical microtubules is observed in the anterior part of the differentiation zone. This is the origin of the crest-like body that appears at the end of spermiogenesis. The presence of striated roots associated with centrioles constitutes the first report of these structures in the spermiogenesis of a cyclophyllidean cestode.