The ultrastructural study of the spermatid differentiation in Cyclina sinensis

The authors have observed submicroscopically the transformation of spermatid and the sperm structure in the spermatogenesis process of Cyclma sinensis. The results show during the spermatid differentiation the nuclear morphology transforms from the elliptical into the cylindrical shape. The morphological transformation of the nuclear chromatin experiences from the small masses of fine granule aggregation to granular substructures with a granular diameter of 20-41 nm (containing a few masses), then to large coarsely granules with a diameter of 36.8-52.6 nm and at last to the homogenate with high electron density. The proacrosomal granules secreted by Golgi complex aggregate to form a large spherical granule which moves gradually to the anterior pole of the nucleus to join the acrosomal formation. The fusion of some mitochondria and the disintegration of a few ones result in the mitochondrial number decrease and volume enlargement. Finally, the mitochondrial ring which consists of five mitochondria and locates at the posterior pole of the nucleus, surrounds the proximal and distal tentrioles to form the main structure of the middle section of sperm. The spermatozoon of Cyclina sinensis is of the primitive type and consists of head, middle section and tail flagellum. In addition, it is of interest to note that a special spherical structure in the subacrosomal area is observed.