The Mediterranean invasive species Calanipeda aquaedulcis Kritschagin, 1873 was discovered for the first time in Svyatoe Lake in the Nizhny Novgorod Region (Russia). This species had not previously been found north of the Kama River estuary near Kazan city (Middle Volga). For comparison, the population from the Tsimlyansk Reservoir (Don River, southern Russia) was also analyzed. Both populations were studied using morphology and genetics (12SrRNA, CO1, nITS and 18SrRNA genes), which showed no differences between them. A morphological description of a male and female invader from Svyatoe Lake with illustrations is provided. Comparison of the invader population by the CO1 gene with material from the Bilbao estuary, Spain (GenBank) showed a difference between these populations of 8.2% nucleotide substitutions, which excludes the Spanish population as a donor for introduction into Russia. Possible sources of invasion and prospects for the dispersal of the invader are discussed.

The Mediterranean invasive species Calanipeda aquaedulcis Kritschagin, 1873 was discovered for the first time in Svyatoe Lake in the Nizhny Novgorod Region (Russia). This species had not previously been found north of the Kama River estuary near Kazan city (Middle Volga). For comparison, the population from the Tsimlyansk Reservoir (Don River, southern Russia) was also analyzed. Both populations were studied using morphology and genetics (12SrRNA, CO1, nITS and 18SrRNA genes), which showed no differences between them. A morphological description of a male and female invader from Svyatoe Lake with illustrations is provided. Comparison of the invader population by the CO1 gene with material from the Bilbao estuary, Spain (GenBank) showed a difference between these populations of 8.2% nucleotide substitutions, which excludes the Spanish population as a donor for introduction into Russia. Possible sources of invasion and prospects for the dispersal of the invader are discussed.