Differences in Midgut Phosphatases Activity and Hemolymph Composition in Lymantria dispar and Euproctis chrysorrhoea Larvae Exposed to the Polycyclic Aromatic Hydrocarbon Fluoranthene

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants that can exert significant effects on living organisms. This study investigated the effects of fluoranthene, a representative PAH, on the activities of alkaline and acid phosphatases in the midgut, and on total lipid and trehalose concentrations in the hemolymph, of larvae of the forest insect species Lymantria dispar and Euproctis chrysorrhoea (Lepidoptera: Erebidae). The results revealed species-specific differences in midgut phosphatase responses to dietary fluoranthene exposure. In L. dispar larvae, the activity of non-lysosomal acid phosphatase decreased at the higher fluoranthene concentration. In contrast, the activities of total acid and lysosomal acid phosphatases increased in E. chrysorrhoea larvae exposed to the lower fluoranthene concentration, consistent with a defensive role. Zymogram analyses revealed different patterns of midgut phosphatase isoform expression in the two species. While lipid concentrations in the hemolymph were unaffected, a significant decrease in trehalose concentration was observed in L. dispar larvae exposed to the lower fluoranthene concentration. Furthermore, fluoranthene exposure resulted in reduced larval mass in both species, indicating the allocation of resources toward defense. These responses specify the significance of relationships between physiological changes and mass reduction in L. dispar and E. chrysorrhoea larvae affected by pollutant, and contribute to understanding their defense mechanisms and energy metabolism for coping with this environmental stressor.