Yurchenko O.V., Radashevsky V.I., Reunov A.A. 2010. Ultrastructural study of spermatogenesis in the Pacific oyster Crassostrea gigas (Bivalvia: Ostreidae) from the Sea of Japan // Invertebrate Zoology. Vol.7. No.1: 55–69 [in English].

A.V. Zhirmunsky Institute of Marine Biology, FEB RAS, Vladivostok, 690041, Russia; e-mail: olyurchenko@yandex.ru

KEY WORDS: Crassostrea gigas, Ostreidae, sperm cells, ultrastructure.

ABSTRACT: Spermatogenesis in the Pacific oyster Crassostrea gigas from the Sea of Japan, was studied with transmission and scanning electron microscopes. Spermatogonia are characterized by two kinds of nuage-like material (large germinal body-like structure and/or cluster of small globules), cisternae of endoplasmic reticulum and prominent Golgi body that gives rise to occasional proacrosomal vesicles. Spermatocytes contain numerous proacrosomal vesicles, while both kinds of nuage-like material are rarely observed at this stage. A large single acrosomal vesicle is formed by fusion of proacrosomal vesicles in the basal part of each spermatid. After migration to the apical position of the acrosomal vesicle becomes cup-shaped; the round nucleus assumes barrel-like outlines. Part of spermatocytes and spermatids develop with flagellum while some spermatogenic cells are characterized by intracellular axoneme. Spermatozoa have an electron-lucent knob situated on top of the acrosome. This type of knob has never been described earlier in the C. gigas and other ostreids. The pattern of C. gigas spermatogenesis which includes many ultrastructural features may be used in future comparative studies of sperm development in Ostreidae and other mollusks.

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