Dynamics of Redox Metabolism during Complete Metamorphosis of Insects: Insights from the Sunflower Caterpillar (Lepidoptera).

Complete insect metamorphosis requires substantial metabolic and physiological adjustments. Although oxidative stress has been implicated in metamorphosis, details on redox metabolism during larva-to-pupa and pupa-to-adult remain scarce. This study explores redox metabolism during metamorphosis of a lepidopteran (), focusing on core metabolism, antioxidant systems and oxidative stress. The larva-to-pupa transition was characterized by increased lactate dehydrogenase and glutathione peroxidase (GPX) activities, coupled with depletion of reduced glutathione (GSH), high disulfide-to-total-glutathione ratio (GSSG/tGSH), and increased lipid peroxidation. As metamorphosis progressed, metabolic enzyme activities, citrate synthase and glucose 6-phosphate dehydrogenase increased, indicating heightened oxidative metabolism associated with adult development. Concurrently, GSH and GPX levels returned to larval levels and GSSG/tGSH reached its most reduced state right before adult emergence. Adult emergence was marked by a further increase in oxidative metabolism, accompanied by redox imbalance and enhanced antioxidant mechanisms. These findings highlight a fluctuation in redox balance throughout metamorphosis, with periods of oxidative eustress followed by compensatory antioxidant responses. This study is the first to identify concurrent changes in metabolism, antioxidants, redox balance and oxidative stress throughout metamorphosis. Our findings extend knowledge on redox metabolism adjustments and highlight redox adaptations and oxidative stress as natural components of complete insect metamorphosis.