Aquatic Threat New Research Blames Pesticides for Demise of Frogs, Amphibians

Article excerpt

Scientists may have found another smoking gun in one of the great international intrigues of modern biology.

In the case of the worldwide disappearance of frogs and other amphibians, the new prime suspect is pesticides, researchers reported here Saturday.

For the first time, scientists have shown how a pesticide can disrupt reproduction in frogs.

"It looks like pesticides are one more nail in the coffin for amphibians," said Brent Palmer, a reproductive biologist with Ohio University, in Athens.

The finding is part of a growing body of evidence that extremely small amounts of pesticides can trigger major health problems in animals, including humans.

The finding was one of many prepared for presentation at the American Society of Zoology meeting, which began Wednesday at the Adam's Mark Hotel downtown. About 800 scientists are attending the meeting, which ends Sunday.

In lab experiments, tiny amounts of the pesticide DDT injected into frogs and turtles disrupted the animals' hormone systems, said Palmer and Kyle Selcer, a reproductive endocrinologist with Duquesne University, in Pittsburgh.

That disruption can make either the animal or its offspring infertile, they said.

"We're talking about populations that are `the living extinct,' " Palmer said. "If they can't reproduce, they will go extinct."

***** Disrupting Life

Palmer, Selcer and other scientists from North America and Europe focused on new evidence that pesticides disrupt the endocrine system, which regulates a wide array of hormones in humans and other animals.

Their research centers on chemicals called "environmental endocrine disrupters." These include widely used chemicals: pesticides, herbicides and such byproducts of manufacturing as dioxin.

These chemicals can have enormous impact on animals and humans even in concentrations less than those that can cause cancer, many scientists say.

Tiny concentrations of endocrine disrupters can seriously impair an organism's nervous and immune systems and its reproductive organs, research shows.

Much of the concern has focused on how chemicals affect embryos. That early stage of life is a critical time. That's when a small clump of identical cells begins to organize into a complex animal with intricately balanced systems.

At the meeting, scientists reported that the chemicals influence sex determination in developing alligators. They may have been the reason a beluga whale from the St. Lawrence River developed both male and female sex organs.

And studies showed that a single, tiny dose of dioxin to a mother rat lowers the sperm count of her male offspring.

Biologists already have shown that endocrine disrupters harm birds, reptiles and fish. …

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