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Impacts of sewage waste wateron feminization and vitellogenin expression in male fathead minnows (Pimephales Promelas) from Indiana waters

Lexis R. Butler, Jason C. Doll, Jessica L. Leet, Jennifer L. Meyer, Paulina Moraga, and Maria S. Sepúlveda. submitted to Proceedings of the Indiana Academy of Science

Estrogenic compounds are commonly found in wastewater effluent. 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). Vitellogenin is synthesized in the liver of egg-laying females after the stimuli of estrogen. Male fish also contain the VTG gene; however, under normal conditions blood circulating estrogens are low enough that VTG in plasma is found at extremely low concentrations. We hypothesized that upon exposure to wastewater from the Muncie Water Pollution Control Facility (MWPCF) adult male fathead minnows (Pimephales promelas) would respond with a decrease in secondary sex characteristics and express VTG if the effluents contained sufficient estrogens. For this purpose, adult males were caged at two sites in the West Fork White River, Indiana: 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” group. After 21 d, different body and organ measurements and secondary sex characteristics were measured and liver VTG gene expression quantified using quantitative polymerase chain reaction (qPCR). While no significant differences were observed in secondary sex characteristics between the study groups, “downstream” males had larger liver somatic indices and showed a VTG up-regulation when compared to the other two groups. These results are in agreement 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.