Saturday, March 6, 2010

Sex-Changing Herbicide Makes Amphibians Sick, Too

Atrazine is receiving lots of attention for turning male frogs into girls, but that’s not all the common herbicide can do. It also weakens amphibian immune systems, leaving the fragile creatures vulnerable to disease.
Though less obvious than gender bending, immunosuppression could also play a part in the worldwide decline of amphibians, which have porous skin and easily absorb chemicals from rain, groundwater and even water vapor.
“Numerous studies have documented the effects of environmental pollutants on the amphibian immune system. Nearly all of these studies suggest that amphibians are particularly sensitive,” wrote Tyrone Hayes, a University of California, Berkeley biologist, in a paper published in the March 15 Journal of Experimental Biology. “In particular, the widespread herbicide atrazine impairs immune function and increases disease rates.”
Hayes is also an author of a March 1 Proceedings of the National Academy of Sciences study on the developmental changes wrought in male frogs by groundwater atrazine concentrations regularly found in the United States, where approximately 80 million pounds of the herbicide are used every year. The frogs had low levels of sperm and testosterone; some even produced estrogen, developed female reproductive organs and were ultimately impregnated by their former gender mates.
The findings are disturbing, but atrazine’s effects don’t end there. As described in the JEB paper, a large body of scientific literature describes how atrazine drives down white cell counts and turns off immune system-regulating genes. Atrazine also suppresses immune function in snails, which often carry amphibian-infesting parasites, and feeds the algae on which snails live.
It’s a perfect storm of infection: atrazine makes amphibians more vulnerable to disease, and carriers of disease more common. Read More

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