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Sexually active fungus "bad news" for frogs


BEIJING, Aug. 7 (Xinhuanet) -- Frogs and amphibians worldwide are being pushed to the brink of extinction by a fungus that can probably reproduce sexually, making it more lethal because it can travel longer distances and stay in the environment longer, a new study finds.

Named chytrid fungus, the pathogen has wiped out frog populations on every continent except Antarctica where no frogs live. It has even spread to protected highland rainforests in Central America.

Though scientists have been following the spread of the fungus, they know little about exactly how it kills off the frogs (though it is thought to clog their skin, essentially suffocating them) and how it has spread to places as distant from one another as Australia and the United States.

The fungus has spread rapidly in the United States. Mountain yellow-legged frogs, once the most abundant amphibians in the Sierra Nevada mountain range, have disappeared from 95 percent of their habitat in the last 30 years. The U.S. Fish and Wildlife Service is considering listing them as an endangered species.

"We found sites dominated by a single fungal genotype, which suggests recent spread of the pathogen through clonal reproduction," said co-author Jess Morgan, a biologist at the University of California, Berkeley, when the study was conducted.

But other sites showed evidence of multiple, related genotypes that suggest that the fungus is reproducing sexually, which could create extremely resistant spores. (Asexual reproduction only takes one parent, which makes a copy of itself, usually by dividing in half. Sexual reproduction combines the genes of two parents, which allows for increasing genetic diversity.)

"This group of fungi, when it reproduces sexually, can create spores that can last for a decade," said study leader John Taylor of UC Berkeley. "That could make this pathogen a harder problem to defeat. As a resistant spore, the fungus could be transported by animals, including humans or birds, or lay dormant in an infected area until a new host comes along."

"This is huge," said frog biologist Karen Lips of Southern Illinois University, who was not involved in the study. "This is really bad news for the frogs."

China View. August 7, 2007.

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