Date of Award
Bachelor of Science
Schistocerca americana, grasshopper, uCT, microCT, tracheal volume, instar, comparative physiology
One major reason for the evolutionary success of insects is their unique tracheal respiratory system. However, during development when oxygen demands are high, the tracheal system may not be able to deliver adequate oxygen to the tissues. In developing grasshoppers (Schistocerca americana), body mass can double during the intermolt period. Also during the intermolt period, jumping performance decreases while jumping muscle lactate production increases, suggesting oxygen delivery problems at the end of the instar. We hypothesize that decreased oxygen delivery during the instar is due to increasing body mass within the rigid exoskeleton compressing the air-filled tracheal system. To test this hypothesis, we identified female sixth instar S. americana.
Similar to previous work, body mass increased 95% during the instar from 0.71g to 1.38g while femur length remained constant at 19.1mm. Using a Bruker SkyScan1272 micro-computed tomography (uCT) system, we scanned grasshoppers during the sixth instar (n=30). uCT image (TIF) files were reconstructed using NRecon and the tracheal system was segmented using Amira 3D and Biomedisa. Total body and tracheal volumes were analyzed using Amira 3D. Tracheal volume decreased by 82% during the instar; early instar tracheal volume was 0.29mL, while late instar tracheal volume was 0.06mL. While tracheal volume decreased, total body volume increased 97%. Therefore, the relative proportion of tracheal volume to body volume ratio decreased from 44.5% to 4.27% during the instar. Our findings that tracheal volumes decrease during the intermolt period support previous work showing that late stage grasshoppers rely more on anaerobic metabolism during repeated jumping.
Sheahan, Andrew, "Decreasing Tracheal Volume during Intermolt Development in Grasshoppers" (2022). Honors Theses. 2633.
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