Photograph by Joel Sartore, National Geographic
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Written By:
Helen Fields
for National Geographic News
Published December 17, 2012
"Scientists have found a new culprit in spreading the disease
that's been driving the world's frogs to the brink of extinction:
crayfish."
The last few decades have proven to be fatal for certain frogs and amphibians due to the disease caused by chytrid fungus, affecting more than 300 species which are now nearly extinct. "This pathogen is bad news. It's worse news than any other pathogen in the history of life on Earth as far as we know it," says Vance Vredenburg, a conservation biologist at San Francisco State University. What has been astounding so far is how chytrid can persist in a frogless
pond. "Researchers saw it happen many times and were perplexed: If all
of a pond's amphibians were wiped out, and a few frogs or salamanders
came back and recolonized the pond, they would also die—even though
there were no amphibians in the pond to harbor the disease."
One possible reason is that chytrid infects other animals. In the lab, Taegan McMahon, a graduate student in ecology at the University of South Florida in Tampa, exposed crayfish to the disease and they got sick. Within seven weeks, over a third died and a large percentage of survivors
were carrying the fungus. She also placed infected crayfish in the water
with tadpoles and they too became infected. When McMahon and her
colleagues went to the wetlands in Louisiana and Colorado, they also found infected crayfish there. This reveals that crayfish may be a sort of reservoir for the disease. The fungus seems to dine on crayfish then attack amphibians when possible.
Although it doesn't seem like it, frogs, and other amphibians, play important roles within the ecosystems they reside in. Without their presence, many pest populations would explode, and so it is vital to discover what will cause harm and what may be a remedy for any grave situation.
- Andrew
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