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Duluth, Minnesota Sewage Effluent Feminizes Minnows

Male minnows placed in Duluth sewage effluent not only developed female characteristics but also lost their male behavior traits and were less able to reproduce, new research revealed. The male fathead minnows lost their aggressive ability to protect nests, fight off rivals and mate with female fish.

The males lost the horns on their heads, their gonads shrank and they began to produce an egg protein found only in healthy females, according to the University of Minnesota study.

The male minnows weren't sterile; they simply didn't have the drive or ability to mate. "Their aggressive behaviors are severely repressed by exposure to effluent," said Dalma Martinovic, a contract scientist for the Environmental Protection Agency's Mid-Continent Ecology Division laboratory in Duluth. She did the research for the University of Minnesota. "Exposed animals didn't reproduce..."
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