Sayenko E.M., Nagel K.-O., Ilyushko M.V., Palatov D.M.
Archiv für Molluskenkunde 2026; 155(2): 185–202
Like other Unionidae species, members of Anodonta have parasitic glochidia larvae. Their complex life cycle, with a parasitic stage for metamorphosis, is characterized by complete morphological differences between the adult mollusk and the glochidium, so that the larval shell offers additional features for identification. The morphology of glochidia may vary among taxa, and such differences can be used to classify unionidans. Using extensive material, including samples from 26 localities in Germany, Kazakhstan, Poland, and Russia, we show that mature glochidia of Anodonta anatina and A. cygnea possess a species-specific microsculpture on their external shell surface: raised loops arranged in clear, parallel rows dorsoventrally in A. anatina, and loops that are not arranged in rows in any area of the glochidial valves in A. cygnea. While glochidia of the two species also differ in average height and length, in practice the size ranges are overlapping and it is impossible to identify the species without scanning electron microscopy. Based on sampling here, the previously predicted presence of A. anatina in water bodies of Krasnoyarsk Region, Tyva and Khakassia Republics (Enisey River basin), and Novosibirsk District (Ob` River basin) in Russia is validated for the first time. In addition to four known localities of A. cygnea in Russia from Kaliningrad Region (Baltic Sea drainage), Voronezh Region (Don River basin, Azov Sea drainage), and Moscow Region (Volga River basin, Caspian Sea drainage), three new localities of A. cygnea have been discovered in the Volga and Oka river basins (Caspian Sea drainage), all in the Moscow Region.
