[The parasite-host relationships between the glochidia of the European pearl oyster Margaritifera margaritifera (Margaritiferidae: Bivalvia) and mass fish species in the European north of the USSR].

Narrow specificity of larvae (glochidia) of Margaritifera margaritifera to salmon in the rivers of the Kola Peninsula was proved experimentally. It was found that in the gills of minnow, the other mass fish in the northern rivers of the USSR, larvae of M. margaritifera cannot develop and perish. Reasons causing the narrow specificity of M. margaritifera to Salmonidae are discussed.