Toxic effects of chromium chloride on hematology and histopathology of major carp (Labeo rohita)

Heavy metal contamination caused by human activities is a major threat to aquatic organisms. Therefore, a 28-day trial was designed to evaluate the hematological and histological changes in Labeo rohita exposed to chromium chloride. For this purpose, 240 fish (Labeo rohita) were randomly selected and divided into four groups. Three groups were treated with a sublethal waterborne concentration of chromium (37, 22, and 11 mgL⁻¹); the fourth group was chromium-free control (0 mgL⁻¹). Results demonstrated that noted values of hematological parameters, such as mean cell hemoglobin, red blood cells, hematocrit, platelets, and hemoglobin, were decreased significantly (P < 0.05) in experimental groups compared with control, while mean cell volume and white blood cells were increased. On the 28th day, a decline was observed in white blood cell values. The severity of histological lesions in the liver, kidney, and gills increased as the concentration and duration of chromium exposure increased. No histological change was observed in the control (T₀), while T₁ showed more severe changes than T₂ and T₃. Those results suggest that long-term exposure to chromium chloride causes adverse effects on the hematology and histology of major carp, Labeo rohita.