Abstract:The morphology of mature egg and sperm of Scophthalmus maximus, and initial stages of sperm penetration were observed under scanning electron microscopy(SEM). The cortex had been observed with TEM. The micropyle consists of a depressed vestibule and a canal. A lot of small holes were found on the vestibule and the outer chorionic surface. Spermatozoon of S. maximus consists of an acrosome-less head, a short midpiece containing 9-14 mitochondria, and a long tail. The speed of sperm penetration was very fast. During 0-5 seconds post insemination, sperm entered the eggs. During the sperm penetration, there were some structure changes, for example, the sperm became bigger, the mitochondria disappeared, and the jagged circle in the inner wall of the micropyle tunnel turned into slippery circle.
