Levels of elastic resilin modulate leg stiffness but not elasticity in Drosophila

Resilin is a highly effective elastic component of the insect cuticle, saving energy, providing flexibility, and protecting chitinous structures against structural damage. In the locomotor system of Drosophila, the protein occurs patchy at various locations of the leg. Here, we genetically enhanced and also eliminated resilin by 34% and -69%, respectively, in the long tendon of Drosophila and quantified leg stiffness and elasticity in a work-loop-based biomechanical testing assay during leg movement. Resilin content little alters leg articulation and posture angles during force loading, while elevated resilin expression enhances leg stiffness 3.9-fold compared to resilin knockout and 2.2-fold compared to wild-type flies. We also found that leg elasticity is unaffected by resilin and discuss our findings with respect to material properties and active neuromuscular control. Collectively, our data fuel future research on resilin-dependent changes in locomotor capacity, efficiency, and energetic costs for leg movement in the behaving insect.