Effects of testosterone and flutamide on reproduction in Brachionus calyciflorus

The effects of testosterone and flutamide on reproduction in Brachionus calyciflorus were studied. Asexual reproduction in B. calyciflorus was not affected by testosterone at different concentrations of flutamide. Flutamide in combination with 0, 25, 50, or 75 µg L(−1) testosterone had a significant effect on mixis rate. The combination of 5 µg L(−1) flutamide with 25 µg L(−1) or 50 µg L(−1) testosterone resulted in a mixis rate that was 2.2× lower than that with flutamide alone. Fertilization rate was significantly decreased by 7.5 µg L(−1) flutamide in combination with 25, 50, or 75 µg L(−1) testosterone. The number of resting eggs produced per mictic female was significantly lower at all concentrations of testosterone. A low concentration of flutamide in combination with testosterone resulted in antagonism, increasing the number of resting eggs produced. However, when testosterone was combined with a higher concentration of flutamide, resting egg production declined. Therefore, long-term exposure to either testosterone, flutamide, or a combination of these two compounds may significantly reduce resting egg production in rotifers. This implies that resting egg production is affected differently by hormone pathways.