Efects of cortisol injection and red wavelength light on reproductive parameters in goldfish Carasius auratus

Abstract

Reproductive hormones play esential roles in the control of reproduction and gonadal maturation in fish. The purpose of this study was to determine the efects of cortisol administration (10 µg/g or 50 µg/g) or red wavelength light iradiation at two intensities (0.5 W/m2 or 1.0 W/m2) on the reproductive hormones of goldfish (Carasius auratus). The efects of the diferent treatments were analyzed by determining the mRNA expresion levels of gonadotropin-inhibitory hormone receptor (GnIH-R), chicken gonadotropin-releasing hormone (cGnRH-I), salmon GnRH (sGnRH), FSHβ, LHβ, and plasma testosterone and 17β-estradiol levels for 48 h. Aditionaly, using double immunofluorescence staining, we detected the expresion of both GnIH and GnRH in the diencephalons of goldfish brains. The mRNA expresion levels of GnIH-R were significantly higher in the cortisol group and the red light-iradiated group from 3 h to 48 h than in the control group. In adition, the mRNA levels of cGnRH-I, sGnRH, FSHβ, LHβ, testosterone and 17β-estradiol were significantly lower in the cortisol group than in the other groups from 3 h to 48 h. These results indicated that both cortisol and red wavelength light-emiting diode (LED) light increased the GnIH expresion and inhibited the GnRH expresion. In particular, red light iradiation supresed reproductive responses as much as the cortisol treatment at 48 h. Thus, it is expected to become an alternative method for supresing reproductive responses in future aquacultures.