Fatty Acid Content and Enzymes of Fatty Acid Metabolism in Overwintering Cold-Hardy Gall Insects

Abstract

Fatty acid content and enzymes of fatty acid metabolism were studied in overwintering larvae of two cold-hardy gall insects, the freeze-tolerant fly Eurosta solidaginis and the freeze-avoiding moth Epiblema scudderiana. Both species increased the proportion of unsaturated fatty acids during the winter. Whereas total lipid content did not change in Eurosta solidaginis, a decrease in total lipids over the winter in Epiblema scudderiana suggested the use of fat reserves to maintain basal metabolism. Changes in the activities of enzymes of fat oxidation correlated with these observations in Eurosta solidaginis: hydroxyacyl-CoA dehydrogenase, carnitine-palmitoyl transferase, and acetoacetyl-CoA thiolase activities all decreased during overwintering. In Epiblema scudderiana the same activities were constant, decreased, or increased. These activities were, however, higher in the fat-oxidizing, freeze-avoiding species than in the freeze-tolerant larvae. Lipid content in Epiblema scudderiana increased again by ear...