How bumblebees can flap their wings so quickly

Nature : Researchers in Japan have used x-ray diffraction to study bee wing movement at the molecular level. They found that insect wing muscles and vertebrate muscles share a common mechanism. Both involve the interaction of several proteins. Motor nerves activate proteins called troponins, which cause another protein, called actin, to rotate and expose areas where the motor protein myosin can bind. Once bound, the myosin curls and pulls the actin, which causes the muscle to stretch. Muscles that move rhythmically, including those in the human heart and insect wings, are sustained by the very act of stretching—as the muscle gets extended, more areas are exposed on the actin for the myosin to bind to. In vertebrates, the release of calcium is what activates the muscle mechanism. However, because it would take too much energy to pump calcium fast enough to sustain insect flight, the researchers propose that insects may have a form of troponin that doesn’t require activation by calcium ions.