Physiology of Finfish and Shellfish (2+1)

3.1.19. Follicular atresia

All the oocytes developing in the ovary of a fish do not reach full maturity and several of them degenerates. These are called atretic oocytes or pre-ovulation corpora lutea and are seen in a section of the ovary during pre-spawning and after spawning period. A number of oocytes are thus lost from the ovary due to degeneration of the oocytes at various stages of maturation. This influences the fecundity or the reproductive potential of the fish. The process of atresia has been seen in a number of Indian teleosts such as Mystus seenghala, Wallago attu, Channa punctatus, Tor sp, Clarius batrachus, H. fossilis etc. Both mature and young oocytes becomes atretic and the follicular cells surrounding them are unable to produce healthy mature ova.