Effects of nonylphenol and 17 beta-estradiol on vitellogenin synthesis andtestis morphology in male platyfish Xiphophorus maculatus

Nonylphenol has been found to exert estrogenic effects in fish and may infl uence the fertility of male fish. In the present study, the effects of nony lphenol and 17 beta-estradiol on vitellogenin synthesis and testis morpholo gy in platyfish Xiphophorus maculatus were investigated. Vitellogenin was o bserved in the plasma of all fish exposed to nonylphenol or 17 beta-estradi ol. Exposure to 17 beta-estradiol resulted in a significant reduction in th e gonadosomatic index. A tendency for a dose-dependent reduction in the gon adosomatic index in the nonylphenol exposed groups was observed. Histologic al examination revealed dose-dependent effects of nonylphenol on the testis structure. The testes of control fish contained numerous cysts with sperma togenetic cells. The testes of fish exposed to nonylphenol or 17 beta-estra diol showed a decrease in the number of cysts concomitant with an increase in the amount of hypertrophied Sertoli cells present. Formation of spermato zeugmata is compulsory for this species, but free spermatozoa were observed in the efferent ducts of the treated fish. The study indicates that nonylp henol has estrogenic potency, and that both nonylphenol and 17 beta-estradi ol have marked effects on the testis morphology of X. maculatus. The ambien t concentration of nonylphenol was measured by high pressure liquid chromat ography during the experiment. The measurements revealed that the actual co ncentrations of nonylphenol in the water were about 30-40 % of the nominal concentrations.