Dude fish looks like a lady — but why?

It seems likely this might be at least part of the reason for declining sperm counts in human men.

http://www.msnbc.msn.com/id/29509301/

By Emily Sohn
updated 2 hours, 51 minutes ago

Around the world, increasing numbers of male fish are developing female traits — growing new sexual organs and sometimes even producing eggs. The phenomenon that has been blamed mostly on chemicals that get into the water and mimic the female hormone estrogen.

But a new study puts some of the blame on an entirely different class of chemicals — ones that block the action of male hormones called androgens.

It isn't the first study to suggest that anti-androgens might be contributing to the feminization of fish. But the new research found that there are far more of these chemicals in our lakes and streams than anyone realized. And anti-androgenic chemicals in the water might affect human health as well.
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Anti-androgenic chemicals usually come originally from pesticides or pharmaceuticals that get into wastewater. Dozens of studies have linked these chemicals with health problems in mammals, said Gerald Ankley, an ecotoxicologist with the Environmental Protection Agency in Duluth, Minn. But this is one of the first studies to make the link in fish.
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the work brings up plenty of questions about what chemicals in our rivers and streams might be doing to human health. After all, people and fish have similar hormonal systems.

"At the end of the day, wildlife are fantastic sentinels for potential human impacts," Tyler said. "If it happens in fish, it can happen in humans."