Sexual behavior and impregnation success of adult male mosquitofish following exposure to 17beta-estradiol.

The effects of 17beta-estradiol (E2) on the sexual activity of adult male mosquitofish (Gambusia holbrooki) were assessed. Sexually mature males were exposed to nominal concentrations of 20, 100, and 500 ng/L of E2 and a solvent control (0.00001% ethanol v/v) for 84 days under continuous flow conditions. Following exposure, males exposed to E2 at concentrations of 20 ng/L and above displayed a lower level of sexual activity, measured as the number of approaches and copulation attempts made toward nonexposed females, than the control males. In addition, E2-exposed males were less capable of impregnating females than the control males. Exposure to E2 had no significant effect on spermatozeugmata production or the secondary sexual characteristics, indicating that the reduced impregnation efficiency of the E2-exposed males was most likely due to the decline in sexual activity.