Chronic changes in developmental oxygen have little effect on mitochondria and tracheal density in the endothermic moth Manduca sexta.

Oxygen availability during development is known to impact the development of insect respiratory and metabolic systems. Drosophila adult tracheal density exhibits developmental plasticity in response to hypoxic or hyperoxic oxygen levels during larval development. Respiratory systems of insects with higher aerobic demands, such as those that are facultative endotherms, may be even more responsive to oxygen levels above or below normoxia during development. The moth Manduca sexta is a large endothermic flying insect that serves as a good study system to start answering questions about developmental plasticity. In this study, we examined the effect of developmental oxygen levels (hypoxia: 10% oxygen, and hyperoxia: 30% oxygen) on the respiratory and metabolic phenotype of adult moths, focusing on morphological and physiological cellular and intercellular changes in phenotype. Mitochondrial respiration rate in permeabilized and isolated flight muscle was measured in adults. We found that permeabilized flight muscle fibers from the hypoxic group had increased mitochondrial oxygen consumption, but this was not replicated in isolated flight muscle mitochondria. Morphological changes in the trachea were examined using confocal imaging. We used transmission electron microscopy to quantify muscle and mitochondrial density in the flight muscle. The respiratory morphology was not significantly different between developmental oxygen groups. These results suggest that the developing M. sexta trachea and mitochondrial respiration have limited developmental plasticity when faced with rearing at 10% or 30% oxygen.