Kisspeptin-10, a neuropeptide present in the brains, ovaries, and testes of zebrafish, plays a critical role in gonadal development and steroid expression. At a concentration of 10 ng/ml, it enhances the mRNA levels for the luteinizing hormone (Lh) receptor and both progestin receptor a (Pra) and Prb in zebrafish ovarian follicles. In female goldfish, doses of 0.1 and 1 µg/g of Kisspeptin-10 elevate serum levels of luteinizing hormone, with no similar effect observed in male goldfish.