Histological analysis of oogenesis and ovarian development of the freshwater crab Sinopotamon henanense.

The morphological and cytological changes of oogenesis and ovarian development were described in the freshwater crab Sinopotamon henanense through macroscopic and microscopic examinations. Serial histological dissections of the ovaries demonstrated that oocyte development was asynchronous. Oogenesis was divided into four distinct stages including six phases: oogonium stage, the first phase (OI) and the second phase (OII) comprising the previtellogenic stage, the third phase (OIII), the fourth phase (OIV) and the fifth phase (OV), comprising the vitellogenic stage and the sixth phase representing the mature stage. Furthermore, examining and analyzing the gonadosomatic indices showed that the developmental cycle of the ovary was closely related to season, and indicated that the breeding season of S. henanense was between May and June. Ovarian development was classified into six stages: proliferation stage, small growth stage, large growth stage, pre-maturation stage, mature stage and spawning stage. Ovaries varied in size and color during each developmental stage, which were closely related to the status and proportions of oogonia and primary oocytes. Although there were cases that oocytes at two or more phases were present at each stage, ovary developmental stages were substantially different. These results provide an important base for studies of the regulatory mechanisms of oogenesis in this compared to other brachyuran species, and will be useful for the aquaculture of S. henanense and related species.