Ultrastructure of Sperm Head Differentiation in the Lizard, Acanthodactylus boskinus (Squamata, Reptilia)

The aim of the present study was to describe the sperm head differentiation in the lizard Acanthodactylus boskinus at the ultrastructural level. For this purpose, five adult male lizards were collected during April and May, 2004 from the desert at the north-east area of Riyadh city, Saudi Arabia. Testes of the lizards were processed for transmission electron microscopy. Thorough observation of the ultrastructural differentiation events of the sperm head has led to a concept of four sequential morphogenetic phases; Golgi phase, cap phase, nuclear elongation and chromatin condensation phase and maturation phase. The Golgi phase is initiated by the proliferation of Golgi complexes in the early spermatids to generate numerous microvesicles and the phase is terminated by the formation of a voluminous acrosomal vesicle. Flattening of the developed acrosomal vesicle over the anterior nuclear portion to form a cap associated with dissolution of the acrosomal granule are the features of the cap phase. Subsequent elongation of the spermatid nucleus accompanied with nuclear chromatin condensation are the features of the following phase. The final maturation phase is characterized by complete chromatin condensation and disappearance of the microtubule manchette. The general features of the differentiation process, which accord with the common criteria of other reptiles, as well as the existing differences are discussed.