Hexavalent chromium induced bioaccumulation, oxidative responses and histological anomalies in freshwater carp Labeo rohita (Hamilton, 1822)

Abstract

The toxicity of chromium, in its hexavalent form (Cr(VI)), is extremely harmful to living organisms owing to its potent oxidizing properties. The present research focused in exploring the hexavalent chromium induced bioaccumulation, oxidative responses and histological anomalies in widely cultured freshwater carp Labeo rohita. Fingerlings of L. rohita were exposed to four sub-lethal waterborne concentrations of 96 h LC₅₀ (1/40th, 1/20th, 1/10th and 1/5th) of the Cr(VI). The impact of chromium was assessed in 5, 15 and 30 days exhibiting significant accumulation (P < 0.05) in the fish tissues (gill > kidney > liver > muscles) with increasing concentration. The bioaccumulation factor (BAF) also exhibited the highest in the liver tissue and least in muscle. Antioxidant enzymes like superoxidase dismutase (SOD) in the gill, liver and kidney increased significantly with the concentrations, while catalase (CAT) activity was found to fluctuate along different concentrations. Significant reduction in growth performance i.e. SGR and reduced feeding intensity was also observed after 30th day. The histopathological examination revealed epithelial hyperplasia in the gill tissues and vacuolization and shrinkage of hepatocytes in the liver tissues. Chromium toxicity-induced alterations in kidney tissues were also characterized by glomerular shrinkage and an increase in Bowman's space. Overall, the study demonstrated that hexavalent chromium exerts significant impact on accumulation, oxidative stress, and histological anomalies, particularly at higher concentrations, in the fingerlings of L. rohita. Therefore, effective treatment of wastewater below the studied concentrations from anthropogenic sources prior to its release into aquatic environments is vital to avert pollution and safeguard the sustainability of aquatic life.

Keywords: Labeo rohita; Antioxidant enzyme; Bioaccumulation; Hexavalent chromium; Histopathology.