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''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 ''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 ''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. ==Life cycle== First intermediate host are ram's horn snails. Second intermediate host are fish and larval amphibians including frogs and salamanders. Inside of amphibians, cercariae are attracted to limb bud regions where the hind limbs form. As a result, large numbers of metacercariae encyst near base of the hind legs. Definitive host are predators such as hawks, herons, ducks, and badgers. The abundance of the teratogenic trematode ''Ribeiroia ondatre'' has been found to increase in eutrophic (nutrient rich) waters. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Ribeiroia ondatrae」の詳細全文を読む スポンサード リンク
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