Analysis of Heavy Metals and Gene Expression of African Arowana Fish (Heterotis niloticus) obtained from Igbalegbe River, Ughelli, Delta State, Nigeria

Heavy metal pollution in aquatic ecosystems can be assessed with suitable biomarkers in fish. This study was carried out to determine the concentration of heavy metals and gene expression of African Arowana Fish (Heterotis niloticus) obtained from Igbalegbe River, Ughelli, Delta State, Nigeria using Atomic Absorption Spectrophotometer (Varian 220 Fast sequential) for the metals and Polymerase chain reaction (PCR) for the gene expression study. Results of the study showed that fishes in the downstream sectionof the river and the effluent discharge point recorded higher metal pollution Index (MPI) compared to the upstream station. The concentration of heavy metals in the fish tissue were generally within the limits of Food and Agricultural Organisation (FAO)/World health Organisation (WHO) except for that of Cadmium and Lead in the discharge station. The selected genes investigated were biomarkers for general stress (HSP70), xenobiotic metabolism (CYPA1), antioxidative defence (SOD), Insulin growth factor-1 (IGF-1) and hypoxia inducible factor (HIF) respectively. The expression of the genes revealed significant variations (P<0.05) in the fishes obtained from the different stations of the river. Some of the genes were down-regulated and suppressed while others were upregulated to enable the fish cope with stress while adapting to environmental pollution. Changes in biomarkers can therefore be considered as early signals of stress in the selected fish species.