Involution processes of follicular atresia and post-ovulatory complex in a characid fish ovary: a study of apoptosis and autophagy pathways

Recent studies seem to indicate that apoptosis and autophagy can act cooperatively in fish ovaries in order to achieve more effective ovarian regression after spawning. Considering the importance of tissue remodeling in ovarian functioning, we sought to morphologically characterize the involution processes of follicular atresia and post-ovulatory complexes using Astyanax altiparanae as an experimental model, and to determine the location of proteins involved in apoptosis and autophagy throughout this process. Fifteen females were collected after reproductive management. Fragments of the left ovaries were removed, fixed, and prepared for light microscopy and immunofluorescence analyses. The main characteristics of the involution processes were found to be consistent with previous descriptions. However, there were certain morphological peculiarities that do not appear to have been described for any other species thus far. These peculiarities may be related to the focus of this study on a single species, which allows for a more detailed investigation into morphological changes than studies on multiple species. Autophagy was also found to precede apoptosis in both involution processes in A. altiparanae. This may be related to the energy recycling process required before the removal of degenerated follicular cells by apoptosis. Thus, these results support the idea that there is crosstalk between autophagy and apoptosis pathways in ovarian involution processes, as well as the idea that the cell death pathways of these processes are conserved between teleost species with external fertilization.