A deadly fungus is attacking frogs’ skin and wiping out hundreds of species worldwide. Can anyone help California's remaining mountain yellow-legged frogs? In a last-ditch effort, scientists are trying something new: build defenses against the fungus through a kind of frog “vaccine.”
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Chytrid fungus has decimated some 200 amphibian species around the world, among them the mountain yellow-legged frogs of California’s Sierra Nevada mountain range.
Frogs need healthy skin to survive. They breathe and drink water through it, and absorb the sodium and potassium their hearts need to work.
In the late 1970s, chytrid fungus started getting into mountain yellow-legged frogs through their skin, moving through the water in their alpine lakes, or passed on by other frogs. The fungus destroys frogs’ skin to the point where they can no longer absorb sodium and potassium. Eventually, they die.
At the University of California, Santa Barbara, biologists Cherie Briggs and Mary Toothman did an experiment to see if they could save mountain yellow-legged frogs by immunizing them against chytrid fungus.
They grew some frogs from eggs. Then they infected them with chytrid fungus. The frogs got sick. Their skin sloughed off, as happens typically to infected frogs. But before the fungus could kill the frogs, the researchers treated them with a liquid antifungal that stopped the disease.
When the frogs were nice and healthy again, researchers re-infected them with chytrid fungus. They found that all 20 frogs they had immunized survived. Now the San Francisco and Oakland zoos are replicating the experiment and returning dozens of mountain-yellow legged frogs to the Sierra Nevada’s alpine lakes.
--- How does chytrid fungus kill frogs?
Spores of chytrid fungus burrow down into frogs’ skin, which gets irritated. They run out of energy. Sick frogs’ legs lock in the straight position when they try to hop. As they get sicker, their skin sloughs off in translucent sheets. The frogs can no longer absorb sodium and potassium their hearts needs to function. “It takes 2-3 weeks for a yellow-legged frog to die from chytridiomycosis,” said mountain yellow-legged frog expert Vance Vredenburg , of San Francisco State University. “Eventually they die from a heart attack.”
--- How does chytrid fungus spread?
Fungus spores, which have a little tail called a flagellum, swim through the water and attack a frog’s skin. The fungus can also get passed on from amphibian to amphibian.
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