In recent years, the frequency of malformed frogs, toads, salamanders and other amphibians found with missing limbs, extra limbs, and skin webbings has increased. The shrinking populations of many North American amphibian populations underscore the need to understand the causes and implications of this phenomenon. Now a new study suggests that a parasite may be to blame for many of the abnormalities found in amphibians of the western United States.

In the research article Parasite (Ribeiroia Ondatrae) infection linked to amphibian malformations in the western United States, appearing in the May issue of the Ecological Society of Americas journal Ecological Monographs, Pieter Johnson of the University of Wisconsin-Madison and colleagues describe the results of their broad-scale field survey. Covering parts of California, Oregon, Washington, Idaho, and Montana, the team of researchers looked for malformations in over 12,000 amphibians representing 11 species of amphibians. The group looked at the relationships between the frequency and severity of abnormalities and a variety of factors in a particular aquatic site, including the abundance of a parasite (Ribeiroia) and pesticide contamination.

The collaborative and interdisciplinary effort, which included academic researchers, as well as federal scientists from the U.S. Geological Survey and the U.S. Fish and Wildlife Survey, found malformed amphibians at a wide variety of aquatic sites, ranging from montane lakes and ephemeral pools to irrigation canals and impoundments. While the researchers did not find a relationship between pesticides and the frequency of malformed amphibians, they did find a striking connection between malformed amphibians and the presence of Ribeiroia.

The presence of this parasite was a powerful predictor of the presence and frequency of malformed amphibians in an aquatic system. The greater an amphibian populations infection with Ribeiroia, the more frequent and
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Contact: Nadine Lymn
nadine@esa.org
202-833-8773
Ecological Society of America
18-Apr-2002

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