Discovery of Unio gontierii (Bivalvia: Unionidae), a freshwater mussel belonging to the crassus-group, on the Black Sea coast of Russia

In the Kherota River (Russian Black Sea coast), freshwater mussels not previously known in the area were discovered and morphologically identified as Unio gontierii Bourguignat, 1856 (Bivalvia: Unionidae). The mussel species identity was verified by analysis of the mitochondrial gene sequence encoding cytochrome c oxidase subunit I (COI). The diversity of the eight studied microsatellite loci in the studied sample was rather high (the average number of alleles per locus was 4.75, the observed heterozygosity was 0.50±0.08). The aforementioned facts, in conjunction with the substantial distribution of the bitterling Rhodeus colchicus Bogutskaya et Komlev, 2001 along the Russian Black Sea coast, whose larvae develop in the bivalves, indicate that Unio gontierii is an indigenous inhabitant of the Russian part of the Caucasian coast and not a recently human-introduced species.