Mutant fungus croaks frog named after Darwin

A hyper-aggressive fungus with some changed up DNA is infecting and killing amphibians.

STORY HIGHLIGHTS

• Aggressive fungus wiping out amphibians worldwide
• It has made some species extinct, including a frog species named for Charles Darwin
• There is another Darwin frog that is now endangered
• The male of the species sort of gets pregnant, the way seahorses do

(CNN) -- Imagine a new plague racing unchecked across the continent, littering the land with human corpses covered with peeling red blemishes. But it equally ravages horses, dogs, cats, monkeys -- every mammal in its path. And it can mutate.

Now be glad you're not a newt, a salamander or a frog -- particularly two species of frogs called Darwin's frogs named after Charles Darwin. Because one of them is now extinct and the other endangered, scientists say.

A hyper-aggressive fungus with some changed up DNA is infecting and killing amphibians, and has done in hordes of these frogs, according to a new study published last week in the scientific journal PLOS ONE.

One of the species, Rhinoderma rufum, was last seen in the wild in 1980. Its close cousin, Rhinoderma darwinii, which Darwin first discovered on his sailing voyage around the world in the 1830s, is endangered.

A few groups of them still live in temperate forests in Chile, in South America, where Darwin found them back then. But now, they are just hanging on.

What the disease has not done to kill them, human activity, including tree farming, has.

In addition to the distinction of bearing the name of the author of the theory of evolution, the frogs are also the only vertebrates aside from sea horses, in which the male of the species sort of gets pregnant.

"The males care for their young by incubating them in their vocal sacs for at least part of their development," the study says. The result is a baby bump.

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The frogs represent merely canaries in the mine as far as the disease is concerned. Virtually all amphibians can catch it. The fungus -- Batrachochytrium dendrobatidis in scientific lingo -- causes a nasty infection.

It is called chytridiomycosis, and scientists have said that it is "the worst infectious disease ever recorded among vertebrates in terms of the number of species impacted and its propensity to drive them to extinction."

And the fungus is genetically flexible. There are many strains of it, with the possibility of new ones popping up.

The most virulent one has recombinant DNA.

It's basically a mutant.