Thermal Stress-Induced Metabolic Shifts in the Parthenium Beetle: An Untargeted Metabolomics Study

This study investigates the metabolomic profile of the Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae), under thermal stress conditions. This beetle is an effective biological control agent against the invasive and toxic weed Parthenium hysterophorus. Metabolomic analysis identified 1277 metabolites, with significant variation observed among control (27°C), heat stress (35°C), and cold stress (15°C) conditions, highlighting distinct metabolic responses to temperature extremes. Heat exposure yielded the greatest number of unique metabolites, indicating elevated metabolic activity, while cold stress also induced distinct compounds, reflecting specialized adaptive responses. Enrichment analysis revealed consistent upregulation of alkaloids, lipids, and amino acid-related metabolites across all conditions, suggesting their protective roles in membrane stability, cellular signaling, and stress mitigation. Pathway analysis showed that lipid metabolism (glycerophospholipids and sphingolipids) and amino acid pathways (tryptophan, phenylalanine, and histidine) were universally affected, likely reflecting adaptive membrane remodeling and stress-response mechanisms that support beetle survival under fluctuating thermal conditions. Control beetles primarily utilized glutathione and carbohydrate metabolism, whereas heat-stressed beetles exhibited enrichment of nitrogen metabolism and amino acid catabolic pathways. In contrast, cold stress uniquely altered nucleotide metabolism and vitamin B6 pathways, suggesting distinct metabolic strategies in response to temperature extremes. Overall, these findings demonstrate that Parthenium beetles undergo extensive, condition-specific metabolic reprogramming to maintain cellular homeostasis and adapt to thermal stress.