DEVELOPMENT AND SUBMICROSCOPIC ANATOMY OF MALE GAMETES IN HALAMMOVORTEX NIGROFRONS (PLATHELMINTHES, RHABDOCOELA, DALYELLIOIDA) - PHYLOGENETIC IMPLICATIONS AND FUNCTIONAL-ASPECTS

The steps of spermiogenesis and the submicroscopic anatomy of male gam etes in Halammovortex nigrifrons are described. During spermiogenesis the cytophore develops pseudopod-like extensions, and bung-like deposi ts of dark material become attached to the basal bodies of the cilia. During the phase of cell elongation, cilia stay near the edge of the c ytophore. Spermatozoa bear two free cilia or flagella. The axonemata a re equipped with glycogen islets appearing at regular spaces. The sper m body is characterized by dot-like dense granules linearly arranged, intense glycogen aggregations in a channel-shaped deposition and giant dense bodies. Events of spermiogenesis and the features of mature mal e gametes in H. nigrifrons corroborate the hypothesis of the existence of a monophylum within the Rhabdocoela encompassing several, but not all taxa of the ''Typhloplanoida'' and ''Dalyellioida''. The Dalyellii dae (including the species of the Temnocephalida) belong to this monop hylum.