Ribeiroia ondatrae

Ribeiroia ondatrae is a parasite in the genus Ribeiroia which is believed to be responsible for many of the recent increases in amphibian limb malformations, particularly missing, malformed, and additional hind legs. In recent studies, it was found that in areas infected with R. ondatrae, the population of amphibian limb malformations was much higher than populations in which this trematode was not present. Each species studied showed varying results. For example, amphibians of species Pseudacris regilla, Rana aurora and Taricha torosa were found to physically display a higher frequency in the number of abnormalities.