Diversity within the Ponto-Caspian Paramysis baeri Czerniavsky sensu lato revisited: P. bakuensis G.O. Sars restored (Crustacea: Mysida: Mysidae)

The Ponto-Caspian mysid crustacean Paramysis bakuensis G.O. Sars, 1895, which was previously synonymized with P. baeri Czerniavsky, 1882, is restored on the basis of new morphological and molecular characters. The Sea of Azov subspecies P. baeri bispinosa Martynov, 1924, in turn, is synonymised with P. bakuensis. The two species, P. baeri and P. bakuensis, are distinguished by the shapes of paradactylar setae of pereiopods, maxilla II exopod and antennal scale, and by the number of denticles in the telson cleft. They also are characterized by ca 7% divergence in mitochondrial COI gene sequences. P. bakuensis is shown to be a widespread species, distributed in estuaries and rivers of the Caspian, Azov and Black Sea basins and in the Caspian Sea itself. P. baeri is endemic to the Caspian Sea, where the two species overlap and are sometimes found together.