Key result
A novel ergometer demonstrated that the Drosophila jump muscle performs work against thoracic stiffness during takeoff, and mutations in sarcomeric proteins reduce jump output.
A novel ergometer allows for direct measurement of the Drosophila jump muscle performance, offering a new model to assess functional consequences of muscle protein mutations.
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Confirms mesothoracic leg dominance in Drosophila takeoff; leaves open extension to vertebrate locomotion models.
We have developed a novel apparatus, an ergometer, to simultaneously measure the horizontal and vertical components of the work done during takeoff by the fruitfly, Drosophila. We confirm the anatomical prediction that all the work comes from the middle (mesothoracic) legs. With all six legs on the ergometer platform, displacement is directed roughly 45 degrees forwards or backwards. Both directions are equally likely. This provides for a random, rapid horizontal component to the escape behaviour for flies. When the thoracic stiffness is reduced (due to a mutation in which the indirect flight muscles (IFM) do not form myofibrils), jump output is increased. We conclude that the jump muscle, the tergal depressor of trochanter (TDT), which lacks direct muscle antagonists, performs work during the jump against thoracic stiffness. Both cuticle and IFM contribute to the thoracic stiffness as the TDT still produces repeated contractions in the absence of the IFM. Degeneration of the TDT due to mutants in three sarcomeric proteins results in reduction of the jump output. In one of these, the myosin heavy chain mutant, Mhc5, we show that degeneration occurs with age. The anatomical characteristics of Drosophila mean that we are recording, for the first time in the intact fly, the output of a single muscle that has high homology to vertebrate skeletal muscle. Developing an ergometer for Drosophila offers novel opportunities to assess the functional consequences of mutations in muscle proteins, synaptic physiology, neuromuscular development and aging.
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Elliott et al. (2007) studied Drosophila jump muscle performance. Mutations in sarcomeric proteins and indirect flight muscles vs. Wild-type/normal thoracic stiffness was evaluated on Horizontal and vertical components of work done during takeoff. A novel ergometer demonstrated that the Drosophila jump muscle performs work against thoracic stiffness during takeoff, and mutations in sarcomeric proteins reduce jump output.
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