Oocyte Differentiation and Reproductive Health of Solitary Tunicate (Styela plicata) from Eastern Coast of Thailand

Histopathological examination is a widely acknowledged technique to assess the reproductive health of aquatic organisms, but it has never been applied tunicate Styela plicata, potential indicator species water quality. In this study, we examined oocyte differentiation S. plicata obtained from eastern coast Gulf Thailand in order provide basic information for future assessment its health. The mature gonad comprised several ovo-testicular convoluted tubes, which each tube was divided into apical and terminal portions. ovarian tissue located part body contained oocytes various stages (asynchronous development type) consisting four phases namely oogonial proliferation phase, primary growth secondary phase (secondary full-growth stages), post-ovulatory phase. Changes morphology follicular cells were described stage. addition, unexpectedly observed high prevalence atretic follicles (24.5%), might indicate damage by environmental stresses. These findings would be useful histology other perspectives.