LOS ANGELES – Around the world, frogs, salamanders and other amphibians are disappearing – and much about their demise has been a mystery. Now, biologists have used decades-old museum samples of frogs, toads and salamanders to track the relentless path of a killer fungus across Mexico and Central America over the last 40 years.
The findings, published online Monday in the journal Proceedings of the National Academy of Sciences, strongly link the amphibians’ disappearance to the fungus.
Although scientists have known for decades that amphibians have been mysteriously dying, by the time they realized the scope of the problem in the 1990s, it was too late for many species.
The fungus, discovered a decade afterward, was later identified as a possible suspect. However, researchers needed more information from the past.
Lead author Tina Cheng, a graduate student at San Francisco State University, wrote, “the sad fact of the matter is that most of the animals are not there for us to study anymore.”
The extensive collection of amphibians at the University of California at Berkeley provided a solution: It contained a trove of frogs, salamanders and other amphibians collected from sites around the world. The researchers could look for evidence of the fungus on the skin of creatures that were jarred and pickled decades ago.
Analysis of swabs revealed some striking patterns: The fungus emerged in southern Mexico in the early 1970s and spread to western Guatemala over the next two decades, then to Costa Rica. The fungus’s path matched the drops in population counts of a variety of amphibian species in those regions.
One theory, Cheng said, is that it was introduced by the African claw-toed frog, imported from Africa for use in former times in pregnancy tests.