Spermiogenesis and testicular cycle of the lizard Tropidurus torquatus (Squamata, Tropiduridae) in the Cerrado of central Brazil

Abstract

We studied the spermiogenesis and testicular cycle of the lizard Tropidurus torquatus, using light and electron microscopy. Males bearing spermatozoa were present practically year-round and spermatogenic activity showed a regenerative phase from late dry season to the end of the rainy season (July to March), with low frequency of initial stages of the spermatogenic cycle, and a brief degenerative phase from April to June, lacking the total regression of seminiferous tubules. These characteristics resemble those from species with continuous reproductive cycles, contrasting with the strongly seasonal reproductive cycle of females. Spermiogenesis includes nuclear elongation, chromatin condensation, acrosomal and flagellar development, and elimination of excessive cytoplasm. We describe some new aspects in the spermiogenesis of T. torquatus, including the interaction between spermatid and Sertoli cell, acrosomal granule, subacrosomal granule, and the fibrous sheath formation. The testicular cycle of T. torquatus is very similar to that of other lizards that inhabit seasonal environments, and its spermiogenesis and ultrastructure of mature sperm display a number of conservative features. version header