Investigation: Fungus may have killed Atlantic Forest amphibians in the 1970s and ’80s

Résumé détaillé

In the 1970s and ’80s, frogs in Brazil’s Atlantic Forest began dying off. Researchers have proposed various causes, from severe cold snaps to acid rain. Now, scientists believe…

In the 1970s and ’80s, frogs in Brazil’s Atlantic Forest began dying off. Researchers have proposed various causes, from severe cold snaps to acid rain. Now, scientists believe they have solved this decade-old amphibian “cold case.” The culprit, it seems, may be the highly contagious pathogen Batrachochytrium dendrobatidis (Bd). It causes a deadly infectious skin disease, chytrid, in amphibians. The investigation was recently published in the journal Molecular Ecology.

Researchers from the U.S. and Brazil studied specimens collected from Boracéia research station in the Atlantic Forest. William Ronald Heyer, a former curator at the Smithsonian in the U.S., had gathered and preserved 370 frogs from 17 species for scientific study during the 1970s and ’80s. But no one collected the amphibians from 1979 to 1982 — a period when there was a drastic decline in frogs.

“There’s a gap right when the decline happened,” said Jack Boyette, who is first author on this new study, a Smithsonian graduate fellow and Pennsylvania State University Ph.D. candidate. “So, we have this really amazing temporal collection before and after the decline.”

When the team analyzed the specimens, they found no trace of Bd in 1978. But from 1983 onwards, it was widespread, indicating a “really rapid expansion,” Boyette said.

In science, there’s sometimes a “detection lag” — and this was one of those cases. Though the pathogen wasn’t described until 1999, it began devastating populations in the 1970s after emerging in Asia. Bd/chytrid has driven declines in more than 500 species across the globe.

It attacks amphibians’ skin, affecting their oxygen intake as well as water, salt, and mineral regulation. Infected frogs can suffer from damage to the skin — such as reddening, excessive shedding or ulcers — as well neurological and behavioral changes.

“The appearance of Bd coincides with these declines, which is about as strong a link as we could possibly get in these inferential historical data sets,” Boyette…

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