OOGENESIS AND OVARIAN DEVELOPMENT IN SEPIA LYCIDAS

In order to enrich the content of reproductive biology and provide theoretical guidance for the artificial breeding of Sepia lycidas, the oogenesis and ovarian development of S. lycidas were observed by anatomical and histological methods. Six months after cultivated in the concrete ponds, the average weight was 256.34 g, and the maximum weight was 457.08 g, only single individuals reached to mature, while the vast majority of individuals were immature. The asynchronous oogenesis of S. lycidas could be divided into four periods, and subdivided into ten stages according to the morphology and size of oocyte, the morphology of follicular cell, and the situation of vitellogenesis. The four periods and ten stages were: oogonia period (oogonia), protoplasmic growth period (no follicular cell, single follicular epithelium s, and double follicular epithelium), interstitial growth period (early stage of follicle penetration, middle stage of follicle penetration, and late stage of follicle penetration), and trophoplasmic growth period (early vitellogenesis, late vitellogenesis, and mature oocyte). According to the morphology of ovary, gonad somatic index (GSI), and percentage of oocyte at different stage, the ovarian development could be divided into six stages, i.e.: pre-formation, formation, small growth, large growth, pre-maturation, and maturation. The duration of reproduction cycle of S. lycidas was 1 year.