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This study used static bioassay to evaluate oxidative and genotoxic effect caused by ethanolic extract of A. philoxeroides in the liver of C. gariepinus as well as the Histopathological damages caused by the extract on the liver, gills and intestine of the fish. LC50 of the ethanolic extract of A. philoxeroides was determined by probit regression analysis. Fishes were exposed to the sublethal concentration of the extract at the rate of 1% and 10% concentration of the LC50 value in replicate for 21days. During the cause of exposure the fishes exhibited some behavioral changes such as erratic swimming pattern, restlessness and excessive mucus secretion. The oxidative stress study revealed that antioxidant enzyme activities were lower in the liver suggesting deficiency of the antioxidant system to compensate for oxidative stress. DNA damage was high in liver of the exposed fish indicating genotoxic effects. The histological structure of the liver of the fish showed the presence of traces to mild onset of nuclei degeneration. The gills of fish exposed to the extract showed severe collapse of the secondary lamella in conjunction with hyperplasia of the pillar cells within the lamella as well as severe atrophy of the cells, degeneration of the primary lamella and severe cellular and structural damages of the gills. The intestine of the fish group exposed to the extract revealed a small amount of PAS-positively stained substances in the lamina propria, mucus cells and the apical borders of the epithelial cells showing the presence of mucous substances. This study concluded that exposure of C. gariepinus to ethanolic extract of Alternanthera philoxeroides have the ability to negatively affect the behavior, suppress the activities of major antioxidant enzymes of the liver thereby causing oxidative stress, with consequent degeneration of liver and gill tissue which expresses its genotoxicity.

Persistent dumping of sawdust on water banks and or directly into water bodies as a consequence of sawmilling activities is becoming alarming. This study therefore evaluated the effect of sawdust extract on some selected physiological parameters such as histopathology and oxidative stress response using O. niloticus as test organism. O. niloticus were divided into four groups based on exposure concentration to sawdust extract (0%, 1/10, 1/100 and 1/1000 of LC50 respectively) in triplicates. Heavy metals composition was evaluated using Atomic Absorption Spectrophotometer. Phytochemical analysis of sawdust, physico-chemical studies of the cultured water, histopathological and antioxidant enzyme activities were carried out using standard methods. Result showed the presence of metals such as iron, cadmium, zinc, copper and magnesium as well as the presence of alkaloids, flavonoids, steroid, phenols, terpenoid, saponin and anthraquinone in the sawdust extract. There was no significant difference in the water temperature and pH of the cultured water of O. niloticus exposed to the varying concentrations of the sawdust. Dissolved oxygen was however highest in the control water and reduced with increase in the concentrations of sawdust extract exposure. Disintegrated lamella was observed in the intestine and gills, and graded necrosis, in the liver of O. niloticus exposed to sawdust extract. There were inhibitions in the activities of superoxide dismutase (SOD) of both liver and kidney of O. niloticus exposed to sawdust extract. Activity of malondialdehyde (MDA) however, increased with increased extract concentration. This study has therefore shown that sawdust extract could cause tissue - organ architectural distortions and induce oxidative stress in O. niloticus.

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