The structure of spined loaches diploid-poliploid complex of Cobitis genera representatives as well as Sabanjeewia aurata of the Eastern Ukraine river systems were investigated by allozyme analysis and cytometry. In total 39 samples and 1412 specimens from the upper left tributaries of the Dnieper River, the Donets Basin, the coastal rivers of the Azov Sea and the Lower Dnieper were studied. We identified the representatives of C. (superspecies taenia) (51,6% of all researched specimens). C melanoleuca (4,1%), S. aurata (1,1%), allodiploids C. (superspecies taenia) × C melanoleuca (0,3%) and two groups of polyploid hybrids (46,4%). EET-group includs mainly C. elongatoides – 2 taenia and C. elongatoides – taenia – tanaitica. EET-group (2,8%) is represented only by C. elongatoides – 2 tanaitica biotype. In the Lower Donets and the Lower Dnieper, there is a zone of introgressive hybridization between C. taenia and C. tanaitica. The structure of settlements differs accordingly to the river basins and has a tendency to decreasing of polyploids frequency respetivly to meridional direction. The analysis of loaches samples from the coastal rivers of the Azov Sea collected in 1938 and samples from the Middle part of the Donets River in 1971 leads to the conclusion that polyploids in mentioned above regions appeared in 1960-1970s. The structure of diploid-polyploid settlements has an alternative character. More often, there is a predominance of diploids or polyploids. The reason of such bipolarity of settlements could be as reproductive displacement so a relatively strong tolerance of polyploids to anthropogenic climate change.