Effects of hypoxia/hypercapnia on the metablism of Callosobruchus chinensis (L.) larvae

Abstract

Insects that are pests of stored products are highly tolerant to low O2 levels (hypoxia) and high carbon dioxide levels (hypercapnia) for long periods, but the underlying mechanism remains unclear. In the present study, we investigated the metabolic profiles of Callosobruchus chinensis (L.) larvae held under 2% O2+18% CO2 (both v/v) for 24, 48, and 96 h using gas chromatography–time-of-flight mass spectrometry (GC-TOF-MS), their corresponding control groups under normoxia were also investigated simultaneously. We found that the relative quantity of 91, 24, and 48 metabolites were altered at these three time periods, respectively. The metabolites were principally carbohydrates, organic acids, amino acids, and free fatty acids, 30 of these metabolites with high accuracy of qualitative identification and biological functions were chosen for further analyses. These were intermediates of the citric acid cycle, glycolysis, fatty acid synthesis, and amino acid metabolism. Based on our results, levels of organic acids increased, while levels of amino acids decreased, suggesting that metabolism was shifting from aerobic to anaerobic. Lipid metabolism may be relatively less important; the number of fatty acids exhibiting significant changes in level was quite small. The metabolic profiles changed dynamically over time, with the largest changes evident for 24 h of hypoxia/hypercapnia, followed by 96 h, and only a little change has been shown on 48 has revealed by heatmap and pathway topological analysis. Therefore, we present direct evidence that the metabolism of insect pests of stored products is influenced by complex environmental stressors.