Semen promotes oocyte development in elucidating ovarian development dynamics in live-bearing fish.

In some vertebrates and invertebrates, semen release factors affecting female physiology and behavior. Here, we report that semen delivered to females is potentially beneficial for promoting oocyte development in a viviparous teleost, . 88% of mated ovaries develop normally and give birth to larval fish, whereas 61% of non-mated ovaries are arrested in the previtellogenic stage. Semen's significant role (p < 0.0001) in promoting oocyte development may involve remodeling follicular cells and regulating the expression of the extracellular matrix, which facilitates cell communication. Furthermore, the ovarian response to semen may influence the brain, affecting hormone release, follicular cell development and steroid production, and crucial for oocyte growth. This mechanism, which could potentially delay maternal investment in offspring until male genetic input occurs to avoid energy wastage, has not been previously described in teleosts. These findings enhance our understanding of ovarian development in viviparous fish, with broader implications for reproductive biology.