OXIDATIVE STRESS AND ANTIOXIDANTS IN OVERWINTERING LARVAE OF COLD-HARDY GOLDENROD GALL INSECTS

Antioxidant and pro-oxidant systems were studied in overwintering larv ae of two cold-hardy gall insect species, the freeze-tolerant fly Euro sta solidaginis and the freeze-avoiding moth Epiblema scudderiana. An increase in the levels of the oxidized form of glutathione suggested s light oxidative stress in both species during the winter, Freeze-toler ant Eurosta solidaginis larvae generally had decreased activities of a ntioxidant enzymes in the winter, indicating that these larvae do not face increased challenge from oxidative stress during the numerous fre eze-thaw events they experience. Instead, existing defences must be su fficient to prevent any damage, By contrast, increased winter activiti es of antioxidant enzymes in freeze-avoiding Epiblema scudderiana sugg est that these larvae must defend against the formation of reactive ox ygen species. This may result from the oxidative nature of winter meta bolism in these larvae, as well as a dependence on lipid oxidation as their fuel over this season, Xanthine dehydrogenase activity decreased dramatically in both species during the autumn, reducing the potentia l for the formation of the pro-oxidant xanthine oxidase. Indeed, xanth ine oxidase activity fell to undetectable levels by winter in Epiblema scudderiana and was not detectable at any time in Eurosta solidaginis .