In vivo length oscillations of indirect flight muscles in the fruit fly Drosophila virilis
We have used high-speed video microscopy to measure in vivo length oscillations of the indirect flight muscles of the fruit fly Drosophila virilis during tethered flight. The changes in muscle strain were measured by tracking the deformation of the thoracic exoskeleton at the origin and insertion of both the dorsal longitudinal (DLM) and the dorsal ventral (DVM) muscles. The mean peak-to-peak strain amplitudes were found to be 3.5% for the DLMs and 3.3% for the DVMs, although the strain amplitude within individual cycles ranged from 2 to 5%. These values are consistent with the small number of previous measurements of indirect flight muscle strain in other insects, but almost an order of magnitude greater than the strain amplitudes used in most biophysical studies of skinned Drosophila fibers. The results suggest that serial compliance within this sarcomere would need to relieve approximately 70% of the total strain in order for individual crossbridges to remain attached throughout a complete contraction-extension cycle.
© The Company of Biologists Limited. Accepted 14 August 1996. Published December 1996. We would like to thank Dr David Maughan for the helpful discussion that inspired this study. This work was funded in part by the David and Lucille Packard Foundation and NSF Grant IBN-9208765 to M.H.D.
Published - CHAjeb97.pdf