SAN FRANCISCO, May 3 (UPI) -- A deadly fungus infecting frogs, toads and salamanders in California is a major cause of a population decline in amphibians around the world, researchers say.
Scientists at San Francisco State University say the poisonous fungus, known as chytrid, is the dominant cause of death in many amphibian species, the San Francisco Chronicle reported Tuesday.
International surveys have found something approaching a mass extinction is striking amphibians everywhere.
About 40 percent of all amphibian species are in decline, the surveys report, and almost 500 species are listed as "critically endangered."
To pin down the role of the fungus in the amphibian population crash, San Francisco State biology graduate student Tina Cheng applied a laboratory technique that is normally used to analyze DNA in living tissue.
Known as PCR, for polymerase chain reaction, she adapted it and detected clear evidence of the chytrid fungus DNA in the skins of both newly collected specimens and old museum specimens collected during an epidemic of the fungal disease in Central America more than 40 years ago.
Cheng said she has tested more than 1,000 specimens for evidence of the fungus Batrachochytrium dendrobatidis, otherwise known as Bd.
"We're documenting the spread of this disease," she said, "and what's so alarming is that Bd attacks so many species that some are now close to becoming extinct."