ABSTRACT
The major sources of urban runoff contamination have been largely attributed to anthropogenic activities resulting from modern rapid urbanization, agricultural practices and industrialization. This has led to the release of various contaminants such as heavy metals into the aquatic ecosystems. This study was carried out to investigate the histopathological effects in benthic and pelagic fish fauna exposed to heavy metals through urban runoff within Benin metropolis. A total number of 15 Clarias gariepinus and Tilapia zillii were collected from Ikpoba River from June to August 2023. Heavy metals (Cd, Ni, Pb, Cr and Co) in the liver of the fish and histopathological studies were estimated using standard method. The results showed an elevated amount of Cd (0.041 mg/kg), Ni (0.498 mg/kg), Pb (0.102 mg/kg), Cr (0.319 mg/kg), Co (0.071mg/kg) and Cd (0.037 mg/kg), Ni (0.686 mg/kg), Pb (0.064 mg/kg), Cr (0.280 mg/kg), Co (0.068 mg/kg) in the liver tissue of Benthic and pelagic fish . The histopathology analysis of fish liver samples, categorized by habitat (pelagic or benthic), uncovered diverse observations. In pelagic samples, some livers displayed congested central veins filled with mononuclear exudates and prominent steatosis in hepatocytes, while others had unremarkable features or focal endogenous deposits. In benthic samples, findings included congested central veins with mononuclear cells or dispersed mononuclear infiltrates, visible sinusoids, and hepatocytes, often accompanied by marked steatosis and focal pigmentation. These variations may signify differing health and environmental influences on fish populations dwelling in distinct habitats, highlighting the importance of considering habitat-specific factors in assessing liver health.
