BIOCHEMICAL AND HISTOLOGICAL EFFECTS ON BRAIN AND KIDNEY OF JUVENILE OREOCHROMIS NILOTICUS UNDER CRUDE OIL EXPOSURE AND BIOAUGMENTATION TREATMENT

Abstract

Crude oil pollution is one of the environmental constrains that produces aqua-toxicological effects which are deleterious to aquatic life. The aim of the research was to investigate toxic effects of crude oil pollution at LC50 and LC90 in brain and kidney of Oreochromis niloticus juveniles (Nile Tilapia) of average weight 8-12g through biochemical and histopathological evaluation, and the efficacy of bioaugmentation using mixed culture of Bacillus sphaericus and Alcaligenes eutrophus on survival and anti-oxidant enzymes in brain and kidney of Oreochromis niloticus in crude oil polluted pond water. The pre-determined lethal concentrations (LC50 and LC90) of crude oil were 0.25% v/v and 0.35% v/v respectively. There was reduced dissolved oxygen, increased conductivity and pH of pond water exposed to different concentrations (0.25%v/v-0.60%v/v) of crude oil. The activities of various antioxidant enzymes (superoxide dismutase, reduced glutathione, and catalase) in the brain and kidney of fish in polluted pond water were inhibited while the levels of lipid peroxidation increased. The brain acetylcholineesterase activity was significantly inhibited (p<0.05) in fish exposed to lethal concentrations of crude oil. Antioxidant activities in fish organs under bioaugmentation treatment in LC50 and LC90 were similar to the results obtained in the control group without oil pollution. The histology of the fish organs in polluted pond water suffered a severe spongiosis of the parenchyma in brain, and a reduced density of the lymphoid compartment in kidney. The histology of fish organs under bioaugmentation treatment in crude oil pollution suffered a mild density of Virchow-Robbin’s space in the brain, and a moderate congestion of the interstitium in the kidney when compared with results in polluted pond water and control group without oil pollution. Bioaugmentation technique has proved to be a powerful tool in oil spills clean-up, and preventing the deteriorating effects of crude oil pollution in fish.