Effects of nonylphenol on plasma steroids, vitellogenin synthesis and sex reversal in Nile tilapia (<i>Oreochromis niloticus</i>) fingerlings

521-528Nonylphenol has been found to exert estrogenic effects in fish and thus interfere with the sexual development causing reproductive dysfunction. In the present study, the effects of nonylphenol on vitellogenin synthesis and sex reversal in Nile tilapia, Oreochromis niloticus were investigated. Vitellogenin was observed in the plasma of all fish exposed to nonylphenol. A tendency for a dose-dependent reduction in the gonadosomatic index in the nonylphenol exposed groups was observed. Histological examination revealed that nonylphenol impairs gonadal growth clearly shown in the testicular development and differentiation which presented testis-ova state. The study indicates that nonylphenol has estrogenic potency induced intersex state in the fish