Comparative stages of atretic oocyte between sesarmid crabs episesarma singaporense and E. Versicolor from Thailand: Implications on reproductive success

Abstract

The oocyte atresia is the primary mechanism responsible for the degeneration and resorptive process as a common groundwork for aquatic animals, but it has rarely been reported in crabs. The present study focused on the characteristics and stages of the atretic oocyte from two important female sesarmid crabs (Singapore vinegar crab, Episesarma singaporense and violet vinegar crab, E. versicolor) during ovarian maturation. A total of 30 female samples from each crab species was collected from the Palian mangrove area of Trang Province, Thailand. The results shared among those crab samples from the primary growth (PG) and secondary growth (SG) phases underwent a degenerative atresia process. The latter atresia stage during SG was also divided into five stages (I, II, III, IV, and V). The degeneration of follicular cell and yolk architecture identified in the SG was highlighted. The number of atresias was compared between E. singaporense and E. versicolor, indicating that there were no significant differences. Observations suggested that the low number of atresia could be associated with the increased reproductive success of two female sesarmid crabs living in natural habitats.