Uncertainty returns over sex-change fish

Last year, scientists thought they’d found out why female fish in some paper-mill–polluted Florida rivers look like males (SN: 1/6/01, p. 8: Macho Waters). They’d discovered androstenedione, a male hormone and a precursor to testosterone, in the water.

Androstenedione probably formed from pollutants and then became concentrated enough to affect the fish, the researchers said.

Now, others are questioning whether androstenedione is the gender-bending agent. Gerald T. Ankley of the Environmental Protection Agency’s National Health and Environmental Effects Laboratory in Duluth, Minn., and his coworkers analyzed polluted water from Florida’s Fenholloway River, as researchers had done in the earlier experiments.

Ankley’s group separated the water–which did contain androstenedione–into different chemical fractions. Each fraction was tested on specially prepared cells that respond in the laboratory to biologically active male hormones.

Some of the water fractions indeed triggered the responses, or androgenic activity. However, none of these fractions contained androstenedione, says Ankley. His team reports its findings in the September Environmental Toxicology and Chemistry.

“We did observe significant androgenic activity in [river] water . . . caused by, as of yet, unidentified chemical components,” says Ankley. His team will continue to search for these chemicals, he says.

John Pickrell is a freelance writer based in Sydney and the author of Flames of Extinction: The Race to Save Australia’s Threatened Wildlife.

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