Preliminary histological studies on the post-spawn development of ovary in the Chinese mitten crab Eriocheir sinensis

From the day when the female Chinese mitten crabs Eriocheir sinensis spawned,the crabs were cultured in lab and sampled for histological observation of the ovary every two days.Actually,before the spawning,the post-spawn development of the ovary in the crabs has begun.During the period from the ovulation until the spawning,most of the oocytes of the Chinese mitten crab have developed to the oocyte I major growth stage.The mean gonadosomatic index(GSI) was about 10%.After the spawning,the ovaries in some crabs were keeping developing;in the other crabs,the ovaries degenerated.On the 7th day post-spawn,the regression was significant not only from the ovarian appearance but also from the histological observation in some crabs.In the other crabs,almost all the oocytes reached the metaphage or the postphage of the oocyte I major growth stage that meant the oocytes were near mature.The GSI decreased.From the 8th day to the 15th day,the GSI increased slowly,and the oocyte developed further.On the 15th day,the mature ovaries and the degenerated ovaries were observed again.