Using micro-computed tomography to investigate development of respiratory structures in Manduca sexta

Oxygen delivery is an important and possibly developmentally limiting factor in insects.  Current research shows a disparity in how respiratory systems develop and how insects invest in respiratory structures throughout development.  Previous methods of measuring tracheal systems carry limitations and potential risks of underestimating or overestimating tracheal volume.  Using micro-computed tomography, we can address this question in a novel way.  To better understand how the tracheal system grows throughout development, Manduca sexta larva are imaged at the beginning and end of each instar.  Previous research showed that oxygen delivery capacity is static throughout an instar, while overall mass and tissue oxygen demand increase throughout each instar.  This could potentially create periods of stress where oxygen demand is greater than oxygen consumption. Preliminary data support the hypothesis that tracheae increase in size only after molting.  This research will help describe the relationship between insect development and respiratory capacity, which is important to understanding normal tracheal system development and how variation in the environment might impact it. This work will be a stepping stone for further research into Lepidopteran respiratory development and pest management directed at manipulating oxygen or respiratory structures to control development.