Effects of 17α-methyl testosterone on the secondary sex characteristics, ovarian histology and production of fish larvae in the Guppy (Poecilia reticulata)

17α-methyl testosterone is an androgenic hormone and is involved in the sexual cycle and is used in increasing growth and masculinization. In this study, effects of different doses of hormones (300, 400 and 1000 mg/kg. diet) with a control treatment (0 mg/kg. diet) on secondary sex characteristics of male fish (Gonopodium index and color) and female (color measurement), the evolution of fish Ovaries and larvae production of guppy (Poecilia reticulate) were studied. Gonopodium index values in males did not show significant differences. The results also indicate increased red pigment in the male and female fish. While increasing the hormone dose, sperm sac was formed in the ovaries and follicles reduced and as a result of it, larvae production was reduced. When the dose was highest, after about 5 weeks larval production was failed. Our results indicate a strong relationship between physiological characteristics of fish and color and secondary sex characteristics.