A Mollusk Planorbarius corneus is an Intermediate Host of the Infectious Agent of Rostand’s «Anomaly P» in Green Frogs

Here we present the first new data about the mysterious «anomaly P» of green frogs (genus Pelophylax) in about 50 years. We established that the gastropod Planorbarius corneus could be an intermediate host (or vector) of the infectious agent of the anomaly P. Symmetrical cases of polydactyly, the anomaly «cross» and heavy cases of the anomaly P, which were previously found in natural populations in the European part of Russia and recently obtained in laboratory, can be caused by this infectious agent. As the most probable cause, we assume a species of trematodes, for which the first intermediate host is P. corneus, from which they infest tadpoles of green frogs.