Abstract:Ultra structure of the spermatozoon of Platichthys stellatus was observed by scanning and transmission electron microscopy. The spermatozoon of P. stellatus consisted of a head, a midpiece and a tail. The head was spherical in shape, of which the main structure was the nucleus. It had no acrosome but had an implantation fossa at its caudal end. The implantation fossa was shallow, with the depth of 1/4 of the nucleus diameter. The nucleus consisted of electron dense chromatin materials, with a head pit and nuclear vacuole whose chromatin was free. The midpiece consisted of the centriolar complex and the sleeve. The proximal centriole and the basal body were arranged at an orthogonal, and in “T” structure, while the basal body was parallelled to the spermatozoon. The sleeve was very shallow, and the deepest point was just 1/3 to the mitochondrion. There were many ellipse vesicles in the sleeve outside mitochondrion. The main structure of the tail was axoneme, which was slim and long. The structure of the tail was of the typical “9+2” model. The flagella were thick, and there were two rows of lateral fins on the flagellum, but the fin was not asymmetrical. There were many different sizes of ellipse vesicles in the flagella cytoplasm, which were of asymmetry. The structure of the flagellum was accommodated for the spermatozoon move.
