Spermatogenesis and Sperm Ultrastructure in the Land Slug Limax flavus (Gastropoda, Pulmonata) from Egypt

Spermatogenesis and sperm ultrastructure are examined and described for the first time in the garden slug Limax flavus (Gastropoda, Pulmonata, Stylommatophora) in Egypt. Spermatogonia show round nuclei with patchy heterochromatin. The primary spermatocytes are characterized by the presence of synaptonemal complexes. The secondary spermatocytes are reduced in size and contain less cytoplasm and clustered stacks of Golgian cisternae with small proacrosomal vesicles lying close to them. During spermiogenesis, electron-dense plaques develop at both the future anterior and posterior poles of the nuclear surface. These plaques determine the apparent antero-posterior axis of the spermatid, the distal plaque indicates the future anterior part of the cell and the basal one the posterior part where an abundant number of mitochondria are aggregated. The mature spermatozoon shows the characteristic sperm features: an acrosomal vesicle supported by an acrosomal pedestal; a helically keeled nucleus, a neck region and a complex elongate middle piece featuring paracrystalline and matrix layers sheathing the axoneme, coarse fibers and glycogen helices.