Cadmium effects on the fitness-related traits and antioxidative defense of Lymantria dispar L. larvae

Cadmium, like many other pollutants, is nondegradable and can be accumulated by Lymantria dispar at a level that affects fitness components, physiology, and development, which could indicate presence of environment pollution by heavy metals. The cadmium effect on fitness-related traits in the third, fourth, fifth, and sixth instar of L. dispar L. was determined. Furthermore, activities of the following antioxidative defense components after the larvae had been fed on the artificial cadmium-supplemented diet (50 μg Cd/g dry food) were assessed: superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APOX), total glutathione amount (GSH), glutathione-S-transferase (GST), glutathione reductase (GR), and the amount of free sulfhydryl (SH) groups. Statistically significant delay of development in the fourth, fifth, and sixth instar and decrease of the larval mass in the third and fourth instar were estimated after the exposure to cadmium through food in comparison to the control. There were no changes in SOD activity of cadmium-treated larvae. Significantly lower CAT, APOX, and GR activities were recorded in the third, fifth, and in the third instar, respectively. At the same time, higher activity was recorded in the sixth instar, while GST activity was higher in the third. GSH content was significantly lower during all instars after treatment but the amount of SH groups was higher in older larvae. The strategy of antioxidative defense and the adjustment or modulation of fitness-related traits in presence of cadmium was dependent on the age of larvae in L. dispar, which might be used in early metal risk assessment in Lepidoptera and other insects.