Impacts of Sewage Waste Water on Feminization and Vitellogenin Expression in Male Fadhead Minnows
Estrogenic compounds are commonly found in wastewater effluents. Exposure of male fish to these chemicals can lead to ‘feminization’, including decrease in secondary sex characteristics and production of female-specific proteins such as vitellogenin (VTG). We hypothesized that upon exposure to wastewater from the Muncie Water Pollution Control Facility, Indiana, adult male fathead minnows (Pimephales promelas) would respond with a decrease in secondary sex characteristics and increased expression of vtg if the effluents contained sufficient estrogens. Adult males were caged at two sites in the West Fork White River: the downstream group was placed directly below the outflow and the upstream group was placed 0.25 km upstream. A third group was housed indoors in aquaria and served as a control. After 21 d, body and organ measurements, secondary sex characteristics, and liver vtg gene expression were assessed. While no significant differences were observed in secondary sex characteristics between study groups, ‘downstream’ males had larger liver somatic index values and showed an up-regulation of liver vtg relative to the other two groups. Although our results agree with a previous study in this same area that found ‘feminization’ of native populations of bluntnose minnows (P. notatus), the estrogenic compounds that elicited this response remain unknown.