Comparative effects of avian and piscine gonadotrophins on gonadal steroidogenesis, and of avian and piscine pituitaries on induction of spermiation and ovulation in the loach and white silver carp

Abstract

This study reports the effects of avian gonadotrophins (GTH) on gonadal steroidogenesis in vitro, and of avian pituitaries on induction of ovulation and/or spermiation in the loach ( Paramisgumus dabryanus and Misgurnus anguillicaudutus) and white silver carp ( Hypophthalmichthys molitrix). Minced testes or isolated ovarian follicles obtained from sexually-mature loach and silver carp, were incubated in Medium 199 at 25 °C for 4 or 12 h, with avian (chicken, duck, turkey, ostrich or goose) luteinizing hormones (LH), follicle stimulating hormones (FSH), or piscine (common carp, grass carp, black silver carp or loach) GTH, under continuous aeration of 95% oxygen and 5% carbon dioxide and shaken at 100 cycles per min. All avian LH and piscine GTH assayed were capable of evoking dose-related responses of testicular testosterone formation and ovarian estradiol-17β formation by the two fish. Avian LH, however, were generally more potent than piscine GTH. All avian FSH tested were inactive. In the loach ovulation experiment, fish were kept under a lighting regime of 12L and 12D at two temperatures (22 °C and 16 °C). Each fish received one intramuscular (i.m.) injection of a dose of one pituitary equivalent of chicken, duck, common carp or grass carp pituitaries. Ovulation rates in the loach treated with avian or piscine pituitaries were over 90%. Most of the loach kept at 22 °C and 16 °C ovulated, 10–14 h and 22–26 h, respectively, after the injections. Controls did not ovulate. In the white silver carp experiment, fish were kept in open ponds. Each fish received two i.m. injections, 6 h apart, of a dose of six pituitary equivalents per injection. The milt production in the fish treated with either chicken or common carp pituitaries was greatly increased. The abdomens of treated female fish became more distended 15 h after the first injection relative to their treatment condition and the controls; induction of ovulation was only partially successful in terms of the number of eggs ovulated. The effects of avian and piscine pituitaries on induction of ovulation and/or spermiation in the two species of fish were indistinguishable. This study indicates that avian LH are highly acceptable by both testicular and ovarian receptors of the loach and white silver carp. Clearly, avian LH are very potent in stimulating gonadal steroidogenesis in a number of teleostean fish. These findings also suggest that avian LH or pituitaries have a potential use in the center of reproduction in aquaculture.