AN ULTRASTRUCTURAL-STUDY OF CRASSOSTREA-ANGULATA (MOLLUSCA, BIVALVIA)SPERMATOGENESIS

The cytoplasm of Crassostrea angulata (collected from the Atlantic coa st of Northern Spain, Galiza, between 1992 and 1993) spermatogonia con tains a few proacrosomal dense vesicles and intermitochondrial round g ranulo-fibrillar dense bodies. In primary spermatocytes, large cytopla smic spaces appear occupied by large round and more scattered granulo- fibrillar dense bodies which are intermingled with cord-like dense str uctures and are in close association with mitochondria and the rough e ndoplasmic reticulum. As a result of Golgian activity, the number of d ense proacrosomal vesicles increases and a flagellum arises from the c entrioles. During the second meiotic division, several round dense bod ies surrounding cord-like dense structures, as well as dense proacroso mal vesicles, were observed between chromosomes. During spermiogenesis , no Golgian activity was noticed, and only the rough endoplasmic reti culum was observed in close association with proacrosomal vesicles. Si milar results were observed for Ostrea edulis (collected from the Atla ntic coast of southern Portugal, Algarve, between 1992 and 1993). Sper matozoa of both species are of the aquasperm type, and although their ultrastructure is quite similar, silver and phosphotungstic acid-chrom ic acid stainings enabled us to clearly distinguish both species at th e ultrastructural level. The different morphological aspects of sperma togenesis in the Pteriomorphia and the use of silver and PTA stainings in the Mollusca are reviewed and discussed.