Assessment of cytotoxic effects and disruption of biological functions induced by heavy metals in the black cutworm, Agrotis ipsilon

Background Heavy metal pollution poses risks to terrestrial food chains. We evaluated biochemical and cellular responses of fifth-instar Agrotis ipsilon (black cutworm) fed castor ( Ricinus communis ) leaves collected from two polluted sites and a reference site. Methods Oxidative damage markers (protein carbonyls and lipid peroxides), antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APOX), and glutathione S-transferase (GST)], the defense-related enzyme phenoloxidase (PO), and metallothionein (MT) were measured in the midgut and brain tissues. Midgut ultrastructure was examined by transmission electron microscopy (TEM). Heavy metals [cadmium (Cd), chromium (Cr), nickel (Ni), copper (Cu), lead (Pb), and zinc (Zn)] were quantified in plant and larval tissues. Results Larvae fed polluted leaves showed marked oxidative damage and altered enzyme activities. Notable bioaccumulation included midgut Cd increases of ~ 1540% (Group 1) and ~ 1740% (Group 2) versus control; brain MT and GST were also elevated (GST in brain ≈ 3× control). TEM revealed mitochondrial lysis, microvillar disorganization and chromatin condensation in midgut cells. Correlation analysis linked specific metals (e.g., Cu, Zn, Cd) to antioxidant responses. Conclusions Dietary heavy metals cause pronounced biochemical and ultrastructural injury in A. ipsilon larvae, supporting their potential use as terrestrial bioindicators.