Living World / Extinction

Something is killing frogs all over the world—or maybe it is many things that are responsible for the widely observed but for the most part poorly documented declines in amphibian populations. Biologists have blamed acid rain, the pollution or eradication of wetlands, and the shrinking ozone layer, but they have found solid evidence in only a few cases. This past year yet another suspect turned up in Panamanian frogs: a previously unknown parasite.

Karen Lips, a biologist at St. Lawrence University in Canton, New York, has been studying tree frogs in the Fortuna Forest Reserve in Panama for the past seven years. During this past year she came across countless dead or dying frogs. She collected and preserved 50 frogs of 10 species and sent them to D. Earl Green, a veterinary pathologist in Maryland.

When Green examined the frogs under a microscope, he saw that their skin had swollen, most notably in a specific part of the lower belly called the drink patch, which acts like a sponge that takes in most of the frog’s water. Looking more carefully, he found a microbial parasite infecting the skin. The frogs also breathe through their skin, and Green suspects that the parasite gradually dehydrates and suffocates them. He doesn’t know if the microbe is a fungus or a protozoan, but it appears to reproduce and spread by releasing spores through the frogs’ pores.

Lips and Green have no idea why the parasite should be decimating Panamanian frogs now in particular—has it been recently introduced to Panama, or is it a native microbe that frogs for some reason have become more susceptible to? Nor do they know whether it affects frogs outside Panama. During the coming year they plan to look for it in frogs from around the world. A very similar parasite has already been identified in frogs in Queensland, Australia.