A quantitative muscle color metric provides a standardized measure of muscle functional state during breakdown in Gryllus lineaticeps.

Abstract

Comparative and evolutionary approaches have advanced our understanding of muscle biology. However, methods for assessing muscle functional state are expensive, technically demanding and difficult to scale. Here, we developed and validated a standardized framework for quantifying insect muscle color during flight muscle breakdown, using the wing-dimorphic cricket Gryllus lineaticeps. Our color metric robustly tracks variation in muscle color across remodeling stages and predicts muscle mass, protein content and enzyme activity associated with mitochondrial abundance. By providing a standardized, accessible and biologically informative proxy of muscle state, this framework not only advances the utility of G. lineaticeps as a model for muscle remodeling, but will also facilitate comparative analyses in systems where direct measurement of muscle function is logistically, technically or financially impractical. More broadly, quantitative muscle color analysis may facilitate comparative, ecological and mechanistic studies of muscle function, dispersal, aging, seasonal plasticity and environmental stress responses across diverse insect systems.