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

## TL;DR

This study shows how the pollutant fluoranthene affects enzyme activity and energy levels in two pest insect larvae, leading to reduced growth.

## Contribution

The study reveals species-specific physiological responses to fluoranthene exposure in two insect species, highlighting differences in defense mechanisms.

## Key findings

- Fluoranthene reduced non-lysosomal acid phosphatase activity in Lymantria dispar larvae.
- Euproctis chrysorrhoea larvae showed increased acid phosphatase activity as a possible defense response.
- Fluoranthene exposure reduced larval mass in both species, indicating resource allocation for defense.

## Abstract

This study investigated the effects of the environmental pollutant fluoranthene on the activity of the digestive enzymes called phosphatases, as well as the level of energy compounds like lipids and trehalose in the larvae of two pest insect species Lymantria dispar and Euproctis chrysorrhoea. In Lymantria dispar larvae fluoranthene reduced the activity of non-lysosomal acid phosphatase, while in Euproctis chrysorrhoea larvae this pollutant caused an increase in the activity of total and lysosomal acid phosphatases. Additionally, the concentration of trehalose, a sugar that provides energy, decreased in the hemolymph of Lymantria dispar larvae exposed to fluoranthene, but lipid levels were unchanged in both species. Importantly, the mass of fifth instar larvae of both species was reduced by fluoranthne exposure, suggesting that this pollutant can negatively impact the growth and development of these common forest pests. These findings can also serve as a foundation for further research on the ecotoxicological impacts of fluoranthene and other similar environmental pollutants on the wide range of organisms including man.

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.