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The Molecular Trigger for High-Speed Wing Beats in a Bee

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Science  13 Sep 2013:
Vol. 341, Issue 6151, pp. 1243-1246
DOI: 10.1126/science.1237266

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At a Stretch

Insect flight muscles are operationally similar to vertebrate skeletal muscles in many ways; however, they are specialized for high-speed, small amplitude oscillations and are activated not by the release and re-uptake of calcium, but rather through stretch-activation. Iwamoto and Yagi (p. 1243, published online 22 August) use a pair of ultrafast cameras to record diffraction patterns and wing beats in the flight muscles of bumblebees and find that stretch activation is a result of myosin and actin dynamics.

Abstract

The high-frequency wing beat of higher-order insects is driven by self-sustained oscillations of constantly activated flight muscles. However, whether its underlying mechanism is based on flight muscle–specific features or on preexisting contractile functions is unknown. Here, we recorded X-ray diffraction movies, at a rate of 5000 frames/second, simultaneously from the two antagonistic flight muscles of bumblebees during wing beat. Signals that occurred at the right timing for triggering each wing-beat stroke were resolved in both muscles. The signals likely reflect stretch-induced myosin deformation, which would also enhance force in vertebrate muscles. The results suggest that insects use a refined preexisting force-enhancing mechanism for high-frequency wing beat, rather than developing a novel mechanism.

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