Environmental stressors have the potential to have large impacts on the metabolic physiology of developing organisms. Changes in developmental oxygen concentration has been shown to influence body size, tracheal volume, and mitochondrial density in insects and can lead to distinct phenotypes associated with those concentrations. For insects that regulate body temperature well above that of the environment (e.g., facultative endotherms), the demand for oxygen is much higher and the impact of developmental stressors is likely more pronounced. Here we examine the plasticity of the respiratory system of a large Sphingid moths, Manduca sexta, that offers substantial ecological service to their ecosystems through pollination and are currently threatened by various anthropogenic impacts, such as climate change. Manduca sexta were chronically exposed to three different oxygen concentrations (10%, 21%, and 30%) during development. Once the moths eclosed they were tested for phenotypic plasticity of whole animal respiration, mitochondrial respiration, flight performance, and flight muscle tracheal and mitochondrial morphology. Our hypotheses are two-fold, if there is significant phenotypic plasticity, we would expect that moths exposed to hypoxia will have a higher capacity for respiration at low oxygen concentrations due to an increase in tracheal surface area. Conversely, we expect that moths raised in hyperoxia (30%) will have lower capacity for respiration due to a decrease in tracheal surface area driven by ROS production. However, if there is limited plasticity due to the high oxygen demand from aerobic endothermy in this system, then there may not be any significant changes to the phenotype.
