DICHLONE-INDUCED OXIDATIVE STRESS IN A MODEL INSECT SPECIES, SPODOPTERA-ERIDANIA

Southern armyworm, Spodoptera eridania, larvae were provided ad libitu m 0.002-0.25% w/w dichlone, 2,3-dichloro-1,4-naphthoquinone (CNQ). Lar val mortality occurred in a time-and-dose dependent manner, with an LC (17) of 0.01% and an LC(50) of 0.26% CNQ at day-5. Extracts of larvae fed control, 0.01, and 0.25% CNQ diets for 5 days were assayed for ant ioxidant enzymes. While 0.01% CNQ had a mild effect, 0.25% CNQ profoun dly increased levels of all antioxidant enzymes that were examined. Th e increases as compared to control were: 5.3-, 1.9-, 3.2-, 2.6-, 2.8-, and 3.5-fold higher for superoxide dismutase, catalase, glutathione t ransferase and its peroxidase activity, glutathione reductase and DT-d iaphorase, respectively. At 0.01% CNQ, the thiobarbituric acid reactiv e substances (TEARS) were similar to the control group. However, despi te the induction from 0.25% CNQ of all enzymes examined, the lipid per oxidation was not attenuated; the TEARS were 29.7% over the control va lue. High mortalities and CNQ-induced pathologies reflected in retarde d growth, wasting syndrome, and diuresis clearly indicated that the in sect sustained severe oxidant-induced injuries before appropriate defe nses were fully mobilized. Thus, this quinone causes an oxidative stre ss in a model insect species analogous to that observed in mammalian s pecies.