Effect of Diet on the Esterase Patterns in the Hemolymph of the Corn Earworm and the Tobacco Budworm (Lepidoptera: Noctuidae)

Abstract

Dependence of esterases in the hemolymph of the third instar on diet was investigated for two species of noctuids, Helicoverpa (=Heliothis) zea (Boddie) and Heliothis virescens (F.). Esterase patterns were separated by polyacrylamide gel electrophoresis into three groups (GI, GII, GIII) based on their relative mobility (Rm). Each species had characteristic bands for each group. Classification of esterases was based on their ability to hydrolyze the following substrates: α-naphthyl acetate, β-naphthyl acetate, α-naphthyl propionate, and α-naphthyl butyrate. Esterases were classified further on the basis of inhibition by the esterase inhibitors eserine, dichlorovos, monocrotophos, and paraoxon. The hemolymph of H. zea contained 27 bands of esterolytic activity; H. virescens had 11 bands. H. zea hemolymph esterases, especially from GIl, were diet-dependent, whereas H. virescens showed little variability in esterase band patterns regardless of group, diet, or both. H. zea had large components of carboxyesterases (33%) (10 bands) and cholinesterases (48%) (13 bands). H. virescens had 64% (eight bands) and 18% two bands), respectively. Protein bands detected in the hemolymph of H. zea (n = 25) showed five characteristic bands. H. virescens (n = 21) had 10 characteristic bands. Comparison of diet changes in H. zea and H. virescens revealed that H. zea had greater sensitivity as indicated by the protein- and esterase-band patterns. Eight protein bands were common to both species, H. virescens showed a greater tolerance to dietary change than H. zea .