CO2 narcosis induces a metabolic shift in Bombus impatiens gynes

Carbon dioxide (CO₂) has pleotropic impacts on insect physiology and behavior. Although diverse, many of these impacts are related to accelerated metabolism. Here we examined the metabolic shift induced by CO₂ using the economically important pollinator Bombus impatiens. In this species, CO₂ applied to gynes induces bypass of diapause and transition into reproduction. The gynes quickly activate their ovaries and start laying eggs. To examine the metabolic shift caused by CO₂ narcosis, we analyzed macronutrient amounts in four tissues (fat body, thorax, ovaries and crop) at three timepoints following CO₂ administration. Our data show lower lipid amount in the fat body and higher glycogen and protein amount in the ovary tissue in the CO₂ treated gynes 10 days following treatment. Glycogen was higher in the thorax of CO₂ treated compared to the untreated gynes, and protein levels in the crop increased over time but not with CO₂ treatment. These data suggest that CO₂ induces transfer of macronutrients and utilization of stored reserved by accelerating metabolism. These physiological shifts are likely to explain many of the pleiotropic effects of CO₂ across insects.