Exposure of juvenile guppies to three antiandrogens causes demasculinization and a reduced sperm count in adult males.

It has been thoroughly established that the fungicide vinclozolin and the persistent DDT metabolite p,p'-DDE, can function as antiandrogens in mammals in a manner similar to the therapeutic antiandrogen flutamide. In mammals, these chemicals bind the androgen receptor and prevent the transcription of the associated genes causing abnormal sexual development and demasculinization. There are few similar studies in fish and so far it has not been demonstrated that these chemicals have any antiandrogenic effects in this group. In the present study, juvenile guppies (Poecilia reticulata) were fed sublethal doses of vinclozolin, p,p'-DDE or flutamide from birth to adulthood. At sexual maturity, we measured a suite of male sexual characteristics that are known to be under androgen control. All three chemicals caused a reduction in the orange display coloration, inhibited gonopodium development, reduced the sperm count and suppressed courtship behaviour, in a manner consistent with antiandrogen action. Only the gonodosomatic index was unaffected by the treatments. In addition, the three chemicals skewed the sex ratio at adulthood and caused delayed maturation. The altered characters are all considered to be important for male mating success and their impairment indicates that antiandrogens may seriously compromise male reproductive fitness.