Effect of cadmium dietary intake on midgut β-glucosidase of Lymantria dispar larvae

Abstract

A crucial enzyme in feeding and survival of Lymantria dispar (gypsy moth) caterpillars is β-glucosidase. Considering that this herbivorous species is one of the most damaging pests, a study of the enzyme that hydrolyzes plant polysaccharides is of invaluable significance. The knowledge of glucosidase alterations helps clarify our understanding of the insect pest feeding strategy in highly polluted environments. We sought to find out whether acute and chronic exposures to cadmium (10 and 30 μg Cd/g dry food), as well as the recovery from long-term treatment, influence the specific activity of midgut β-glucosidase. Cadmium ingestion did not alter enzyme activity compared to control, regardless of the treatment duration and metal concentration. The only statistically significant increase in enzyme activity was detected during the recovery after chronic treatment at 10 μg Cd/g dry food compared to the chronic cadmium effect at the same metal concentration. During chronic treatment at a lower cadmium concentration (10 μg Cd/g dry food), the phenotypic plasticity index was higher than at the recovery from the same concentration, while the variability of plasticity among these treatments was higher after recovery. Only one enzyme isoform was detected, which indicates its ability to hydrolyze several substrates. We concluded that this enzyme is probably essential for larval nutrition and survival in the presence of high amounts of cadmium in the food.