Abstract
The discovery of a shell of the Chinese pond mussel in 1998 and further confirmation of this species indicate that a reservoir with natural thermal conditions is the oldest species location in Poland. Growth increments of an archival shell do not fall within the ranges obtained by this species in Konin lakes. They are, however, close to population ranges from Hungary. In contrast to other specimens found, the analyzed shell has a very high H/L ratio and is thicker. The observed features might result from the founder effect or they might point to a considerable plasticity of the species.