Population structure and growth parameters of Prussian carp (Carassius auratus gibelio) were studied in 12 freshwater ecosystems of the Donbass region (Eastern Ukraine). These ecosystems differed significantly with respect to their surface area, water transparency and annual concentrations of phosphorus and nitrogen. Amongst the studied ecosystems, diploid males and females as well as a smaller percentage of triploid females were found. The population structure of C. a. gibelio varied significantly in terms of the percentage of triploids and sex ratio amongst diploids. A considerable proportion of triploid females ([10%) was found in four ecosystems with intermediate surface area (38-50 ha) and relatively high growth rate of specimens. The sex ratio amongst diploids was significantly femalebiased in seven of 12 ecosystems, including those where triploids were present in considerable numbers. The growth parameters of Prussian carp were significantly correlated with ecosystem characteristics, but the growth patterns of diploids and triploids were not significantly different from each other. The restricted distribution of triploid specimens suggests that the triploid form might counter diverse environmental challenges, whereas the diploid form of Prussian carp seems to be efficiently adapted to a wide range of ecosystem conditions.

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A total of 205 COI sequences and 310 cyt b sequences of the threespine stickleback (Gasterosteus aculeatus) from basins of all seas throughout the vast range of this species were analyzed. Median networks of haplotypes constructed in this study, combined with the results of reconstruction of paleogeographic conditions, led to the conclusion that the threespine stickleback emerged as a species in the Pacific Ocean basin and spread to Europe from the south, populating the system of water bodies that existed in the Oligocene. The main water body was the Paratethys Ocean (Sea), which existed 5–34 Mya. In the area of the modern North Sea, stickleback populations, part of which later migrated to the eastern and western coasts of North America, gave rise to the group of haplotypes that has the widest distribution in northern Europe. The stickleback populations belonging to the lineage that dispersed along the Arctic and western coasts of North America displaced the carriers of the haplotypes of the ancient phylogenetic lineage that inhabited the Pacific coast. The ancestors of G. wheatlandi dispersed from the Pacific to the Atlantic Ocean via the Arctic to meet G. aculeatus, which circled the globe from east to west.

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