OVARY DEVELOPMENT AND OOGENESIS OF NEOMYSIS JAPONICA
日本新糠虾(Neomysis japonica)卵巢发育与卵子发生

The anatomy and histology of reproductive system of female Neomysis japonica were observed. The developmental stage and the correlation between ovary length and body length were studied. The results show that the reproductive system of female N. japonica is H-shaped and includes an oviduct. The ovary includes the left and the right parts connected by a proliferation center. The oogonias and follicle cells are originated from the germinal epithelium of the center. The volumes of the marsupium and the ovary increase with the ovary development, while that of the proliferation center decreases. No connective tissue was found in the solid portion of the ovary. The volume of oocytes in the left or right part is larger than that of oocytes in the proliferation center. Oogenesis could be divided into five stages: oogonium, previtellogenic oocytes, endogenous vitellogenic oocytes, exogenous vitellogenic oocytes and mature oocytes. The oocytes in the left and the right part of the ovary are the same type in the same stage. The oocytes in early development stage distribute mainly in proliferation center, but only one in the left or the right part. In addition, the ovary development could be also divided into five stages: inactive stage (ovaries containing oogonias, 18d), minor growth stage (endogenous vitellogenic oocytes occur, 22d), major growth stage (exogenous vitellogenic oocytes occur, 25d), mature stage (mature oocytes occur, 28d), and spawn stage (after oviposition, 32d) during which many oocytes retrogress without hyperplastic fibrous connective tissue and surrounded by many layers of follicle cells. The follicle cells and oocytes are fused in late ovarian stages. The oviduct is connected to the ovary end, and opens at the sixth pereiopod anlage. The oviduct lumen became larger with the ovary development. The ovary length and body length were positively related during the whole ovary development.