Ultrastructural study of the spermatogenesis ofAnodonta cygneaL. (Bivalvia, Unionidae)

Abstract

The ultrastructure and development of the male germinal cells of Anodonta cygnea are described for the first time. There are intercellular bridges and multinuclear structures from the early stages until the end of the spermatogenesis. The spermatocyte presents a long axonemal microtubular arrangement in the cytoplasm which will form the flagellar axoneme. During spermatid differentiation, pro-acrosomal vesicles appear to migrate towards the anterior region of the cell. Later these vesicles fuse into an acrosomal vesicle. The spermatozoon is of the primitive type, with a very reduced acrosome. The middle piece shows the centriolar complex and pericentriolar satellites surrounded by five mitochondria located at the same level. Phagocytic cells extend from the basal lamina and have large heterophagic vacuoles filled with phagocytozed material.