Cytomorphological indicators of common roach (Rutilus rutilus Linnaeus, 1758) erythrocytes in the Konoplyanka River

The cytomorphological parameters of the blood erythrocytes of the common roach (Rutilus rutilus Linnaeus, 1758) were studied in the technogenically altered Konoplyanka River. This river is subject to techno-anthropogenic pressure. The analysis was conducted based on samples collected during the summer-autumn period of 2022–2024 at four points along the river, differing in pollution levels. The sampling points were selected to cover the area of tailings storage facilities, the river’s confluence with the Dnipro Reservoir, and a designated conditional control point: № 1 – upper section of the tailings storage; № 2 – lower section of the tailings storage; № 3 – old riverbed; № 4 – river mouth. The concentrations of zinc, copper, and nickel in the Konoplyanka River water exceeded the maximum permissible limits at all studied points. High cadmium content was observed at points № 1 and № 2, while a high concentration of manganese was recorded at point № 1. The lowest concentration of heavy metals in the river water was observed at point № 4. Based on hydroecological, radioecological studies, and heavy metal content analysis, point № 4 (the river mouth) was chosen as the conditional control point. Morphometric analysis of roach erythrocytes revealed that the highest indicators were observed in fish sampled at № 1 (upper tailings storage). The erythrocyte area in fish from point № 1 was approximately 19,9% larger compared to those from point № 4 (conditional control), while the nuclear area was 35,8% larger. The nuclear-cytoplasmic ratio (NCR) of the roach red blood cells ranged from 0,180 to 0,204, with the highest indicators recorded in fish from points № 1 and № 2, exceeding the indicators of fish from № 4 by 13,3% and 12,8%, respectively. The following pathological changes in the erythrocytes of the common roach were identified: poikilocytosis, cytoplasmic vacuolization, hypochromia, nuclear shadows, scalloped membrane edges, and erythrocyte agglutination, which were the most frequently observed. Less commonly, schistocytosis and cell membrane rupture were detected. Among nuclear anomalies, erythrocytes with eccentrically located nuclei were observed. Additionally, pathological changes indicative of the onset of amitosis in red blood cells were recorded in the examined fish. Our research demonstrated that all analyzed blood smears of the common roach exhibited various pathological changes in erythrocyte structure due to significant anthropogenic impact and the poor ecological condition of the Konoplyanka River. The obtained results confirm that cytomorphological blood analysis in fish is an effective tool for assessing the level of water pollution and the physiological state of fish.