Pagrosomus major larvae were exposed to the water soluble fraction of hydrocarbon in No.0 diesel oil (corresponding to No.2 fuel oil) at concentrations of 0, 0 17, 1.22 and 8 82 mg/L for up to 15 days. Larvae were sampled on days 9 and l5 of the experiment. Supernatants of viscera tissue extractions were assayed for biochemical response in terms of oxidative stress superoxide dismutase(SOD), activity of selenium dependant glutathione peroxidase(Se GPx) and catalase(Ca), and the concentration of reduced glutathione(GSH). On day 9 of exposure, statistically significant dose related increases in Se GPx and SOD activity, and GSH concentration were observed in all cases except for Se GPx activity under the highest dosage of hydrocarbon. However, on day l5 of exposure, a similar dose related response was only observed for Se GPx activity. GSH concentration decreased and SOD activity showed no statistical difference as compared to controls. However, a significant decrease in compared to day 9 Se GPx activity and GSH concentration, in contrast to increase SOD activity at day 15 as indicates an accelerated accumulation of H 2O 2 and potential oxidative damage under long term exposure of larvae to hydrocarbons. No statistical changes were observed in Ca activity throughout the experiment, possibly owing to the high efficiency of Se GPx. A recovery experiment was performed on indicating that the response of antioxidants measured tending to return to their control levels. These results prove the function of the antioxidant defense system of the larvae to the water soluble fraction of hydrocarbons in No.0 diesel oil.
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