Acute Cadmium Toxicity Induced Impairments in the Liver and Kidney of Freshwater Catfish, Heteropneustes fossilis (Bloch)

Background / objective: The heavy metal, Cadmium enters aquatic environment through natural / anthropogenic sources and exerts deleterious effects in fish. Hence, the present study is aimed at investigating the acute Cd toxicity induced histological alterations in the liver and kidney of catfish, Heteropneustes fossilis. Methods: The bioassay was performed in a static renewal regime with H. fossilis exposing to varying acute toxicity concentrations viz., 18.45, 36.9, 73.7, 147.4 and 294.8 mg/l for 96 h. The LC50 was determined to be 44.13 mg/l. Since 100 % mortality occurred in the highest concentrations after 96 h, liver and kidney tissues were collected from fish exposed to the first three lower concentrations. Standard histology protocol was followed to study the histological alterations. Findings: The histological alterations like increased kupffer cell and pycnotic nucleus, ruptured hepatic tissue and nucleus, cellular necrosis and focal necrosis were observed in the liver of fish exposed to Cd. Similarly, vacuolation, increased periglomerular and peritubular space, shrunken glomerulus, melanomacrophages and loss of cytoplasm were observed in the kidney of fish treated with Cd. The intensity of the histological alterations in both liver and kidney was found to be concentration and duration dependent. Hepatic tissues were found to be ruptured in the liver of fish exposed to all the three concentrations viz., 18.45, 36.9 and 73.7 mg Cd/l. The appearance of melanomacrophage aggregates is a generalized non-specific marker, indicating environmental stress. In the present study, melanomacrophages were observed in kidney of fish exposed to 36.9 and 73.7 mg Cd/l. Our present observations on histological alterations in the liver and kidney of H. fossilis were in conformity to the histological observations made in the liver and kidney of various fish species exposed to different toxicants. Applications: The histological alterations in liver and kidney H. fossilis induced by Cd suggest that Cd can be a potential toxicant and hence these alterations can be used as biomarkers to monitor aquatic pollution.