Ultrastructure of spermiogenseis and spermatozoa of Taenia parva

We studied the ultrastructure of spermiogenesis and of the mature spermatozoon of Taenia parva, an intestinal cestode of the common genet, Genetta genetta. Spermiogenesis in T. parva is characterized by the growth of the axoneme externally to a cytoplasmic extension. After a slight rotation, the free flagellum fuses with the cytoplasmic extension. This pattern corresponds to type III spermiogenesis according to the scheme proposed by Bâ and Marchand. The zone of differentiation lacks both striated roots associated with the centrioles and the intercentriolar body between them. Nevertheless, the flagellar rotation of about 45 is observed in this species. On the other hand, the mature spermatozoon of T. parva, as in other cestodes, is filiform, tapered at both extremities and lacks mitochondria. The presence of a single crest-like body, periaxonemal sheath, and transverse intracytoplasmic walls are also characteristic ultrastructural features. The pattern of spermiogenesis and the ultrastructural organization of the spermatozoon of T. parva are compared with the available data on cyclophyllideans and, in particular, species of the family Taeniidae.