THE OVARIAN DEVELOPMENT PATTERN OF POND-REARED CHINESE MITTEN CRAB, ERIOCHEIR SINENSIS H. MILNE-EDWARDS, 1853

Although pond culture is the major culture method for Chinese mitten crab (Eriocheir sinensis) in China, the pattern of ovarian development in pond-reared E. sinensis remains unclear. This study investigated the changes in ovarian morphology and histology, gonadosomatic index (GSI), hepatosomatic index (HSI), and monthly variation of the ovarian development pattern during the ovarian maturation of pond-reared female E. sinensis. Based on the pubertal moult, and ovarian morphology and histology, the ovarian development cycle of E. sinensis could be divided into five stages, i.e., Stage I: the ovary appears thin ribbon-like and translucent, dominated by oogonia (OG) and previtellogenic oocytes (PRO); Stage II: the ovary appears milk white or buff, dominated by endogenous vitellogenic oocytes (EN); Stage III: the ovary appears orange or light brown, dominated by exogenous vitellogenic oocytes (EX); Stage IV: the ovary appears crimson red or brown and ovarian lobes occupy most available body cavities. The major oocytes were nearly mature oocytes (NO); Stage V: the ovary appears deep purple and is filled with mature oocytes (MO). During ovarian maturation, the GSI increased significantly and a significant, positive correlation was found between the GSI and the mean long diameter of the oocyte from stage III to stage V. However, a significantly negative correlation was found between GSI and HSI. The ovarian development of pond-reared female E. sinensis was not synchronous, most of the pubertal moults were found until mid-late August. At the end of August, the percentages of females that reached ovarian stages II and III were 55 and 24%, respectively. After that, the ovarian development of pond-reared female E. sinensis became fast, and females with stage III or more advanced ovaries were found to be in excess of 80% by the end of September and onward. From the end of November to late December, the GSI of female E. sinensis did not increase significantly, which indicated pond-reared females had reached mature or nearly-mature ovaries by the end of November.