Toxicological Response of Poecilia reticulata  , Hyla   species and Culex   species to Leachates from Olusosun Landfill, Lagos State, Nigeria

The effect of leachate samples from Olushosun dumpsite in Ojota, Lagos on the toxicological response of Poecilia reticulata, Hyla and Culex species was investigated using acute and chronic toxicity tests. Physicochemical parameters were analysed in the leachate prior to toxicological assessment against test animals. Computed results showed that pH 7.62 while the acute toxicity assay of leachate sample against test animals revealed a 96hr LC₅₀ of 71.53ml/L, 58.34ml/L and 60.643ml/L for Poecilia, Hyla and Culex species respectively. On the basis of the 96hr LC₅₀ values, the leachate was found to be more toxic against Hyla than Poecilia. The exposure of the Poecilia and Hyla species to sub-lethal concentrations (1/10^th of 96hrs LC₅₀) of leachate revealed varied biochemical responses over a 28 day period. The activity of Catalase, Superoxide Dismutase (SOD), Malondialdehyde (MDA) and Glutathione-S-Transferase (GST) showed significant increase (p<0.05) when compared to control in Hyla while the activity of GSH, SOD and CAT showed significant increase (p<0.05) when compared to control in Poecilia sp. Results from this study showed that leachate can induce adverse environmental effect on organisms. The acute and chronic toxicological response of the test animals could be incorporated into risk assessment of dumpsite leachate, design and management of landfill sites.

Keywords
Leachates; Poecilia reticulata; Culex species; Malodialdehyde; Glutathione-S-Transferase