Ribeiroia ondatrae is a parasite in the genus Ribeiroia, class Trematoda, Phylum Platyhelminthes, believed to be responsible for many of the recent increases in amphibian limb malformations, particularly missing, malformed, and extra hind legs.
In recent studies, it was found that in areas infected with the trematode Ribeiroia 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 Hyla regilla, Rana aurora and Taricha torosa were found to physically display a higher frequency in the number of abnormalities.
The exact mechanism of deformation has not been determined but it has been theorized that deformation results from mechanical disruption of the cells involved in limb bud formation during the amphibian larval stage.
Read more about Ribeiroia Ondatrae: Life Cycle, Enhanced Transmission, Location of Infection On Amphibian Species, Species Infected