Nutrient deficiencies and the gypsy moth, Lymantria dispar: effects on larval performance and detoxification enzyme activities

We investigated the consequences of specific nutrient deficiencies for growth performance, food processing efficiencies and detoxication enzyme activities in larvae of the gypsy moth, Lymantria dispar. Larvae were reared on one of four artificial diets, including a low wheat-germ control diet, and protein-, mineral- and vitamin-deficient diets. Growth of fourth instars was reduced on each nutrient-deficient diet; reductions were attributable to decreased efficiencies of conversion of digested food. Larvae on the low protein diet exhibited compensatory feeding responses, but not great enough to offset the reduction in protein intake. The low protein and low mineral diets prolonged development time of females, and reduced pupal weights of males and females. All larvae fed the low vitamin diet succumbed to a nuclear polyhedrosis virus late in the fifth larval stadium. We observed few significant effects and no clear-cut patterns of response of detoxication enzymes to nutrient limitation. Polysubstrate monooxygenase and glutathione transferase activities were unaffected. Soluble esterase and carbonyl reductase activities tended to increase in response to protein deficiency, but decrease in response to vitamin deficiency. Phytophagous insects evolutionarily adapted to feeding on nutrient-poor but allelochemical-rich host plants may have evolved biochemical/physiological mechanisms that serve to maintain effective enzyme function in the context of nutrient deficiency.