A precise comparison of developmental series of oocyte growth and oocyte maturation between real-oocytes and pseudo-oocytes in the coral Galaxea fascicularis

In this study, we histologically investigated the late stage of oogenesis, spermatogenesis, and pseudo-egg development processes of the pseudo-dioecious coral Galaxea fascicularis to form a base from which to elucidate the mechanisms of coral sexual reproduction. This coral has a large egg size and individual polyps, which are suitable for studying the mechanism of sexual reproduction . The histological analysis revealed that germinal vesicle breakdown of this coral begins 3 days before spawning in both female oocytes and male pseudo-oocytes. Spermatogonium, spermatocytes, spermatids, and sperm were observed in the male testicular lobules from 2 months to 1 day before spawning. The findings of our study might allow for the elucidation of the mechanisms of sexual reproduction in this species and facilitate the development of methods for its aquaculture.