Pollutants shape baby-gator gonads

From New Orleans, at the e.hormone 2003 Conference

Over the past decade, comparisons of alligators from two Florida lakes–the relatively pristine Woodruff and the pesticide-laden Apopka–have turned up numerous reproductive impairments in the Apopka animals. Low hatching rates, abnormal sex-hormone concentrations, perturbed egg production, and shorter-than-usual penises, are among the effects observed over the years (SN: 7/15/95, p. 44).

These impacts in Lake Apopka’s animals had been chronicled only in adolescent and adult gators. Biologists at the University of Florida in Gainesville wanted to see whether the changes occur even in baby gators. So, Teresa Bryan and her coworkers collected 150 alligator eggs from nests on Lake Woodruff and incubated many of them in water laced with nine hormone-mimicking pesticides typical of Lake Apopka. Those include DDT, dieldrin, toxaphene, heptachlor, and alpha-chlordane.

To the researchers’ surprise, the pollutants left year-old male gators–the developmental equivalent of human toddlers–with bigger-than-normal phalluses, not smaller ones.

Bryan studied males and females, which both develop phallus-shaped sex organs. Untreated baby males and those getting a half-strength recipe of the pollutants had phalluses about 3.2 millimeters long–0.4 mm shorter than those in males incubated in the full-strength mix of pesticides. Exposure to the pollutants didn’t affect lengths of the baby female’s organ called the clitero-phallus, although part of the organ was wider in animals getting the full-strength mix.

Bryan now suspects that the babies process the pollutants differently than older animals do. In the youngest gators, she says, “the contaminants are acting as [excess] androgens.”


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Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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