Biochemical profile and gene expression of Clarias gariepinus as a signature of heavy metal stress

Heavy metals have been found in increasing concentrations in the aquatic environment. Fishes exposed to such metals have altered gene expression, serum profiles, tissue histology and bioindices that serve as overall health biomarkers. The heavy metals (Ni, Cd, and Cr) accumulated in water and fish tissues, were beyond the permissible limits defined by the Central Pollution Control Board/World Health Organization. Metallothionein (MT) and glutathione peroxidase (GPX) genes expression patterns highlighted the metal-specific exposure of fish. An increased fold change of genes against beta-actin serves as a potential feature for toxicity. Metal toxicity is also reflected by an increased level of digestive enzymes (amylase and lipase) in the serum and alterations in values of reproductive hormones (11-Ketotestosterone and progesterone). Total serum bilirubin attribute to the liver and biliary tract disease in fishes. Histopathological studies show cellular degeneration, breakage, vacuolization signifying the chronic stress.