What they found was that when a moth flaps its wings, a bit of a tug of war is happening at a molecular level. Filaments of myosin tug on filaments of actin to contract a muscle strand, then detach to lengthen the strand. When connected and contracting, the filaments form a lattice-type structure, which is "rubbery," and stores elastic energy. It's like a microscopic trampoline, waiting for something to bounce on it. So when a muscle is contracting, it is acting more like a spring waiting to release its energy than a motor.
Using the APS, Daniel and his team observed that the top of the moth's thorax, which is the muscle that makes the wings move, was cooler on top than on the bottom. The interesting part was that in the cooler regions, the filaments stayed connected for longer, maintaining the rubbery structure for a longer period of time. The elastic energy stored in these cooler regions is released at the end of the lengthening or shortening phases of the muscle. Think of it as a ball finally bouncing on that trampoline. This energy transfer process allows the moth to fly without expending a large amount of energy.
Daniel says that the presence of elastic energy was not a surprise.
"It was not a question of whether or not there was elastic energy involved in flight," Daniel said. The energy cost of rapidly accelerating and decelerating wings during flight is enormous and no insect would be able to maintain that kind of energy output.
However, this study uncovers a new mechanism for this elastic energy storage, one based on temperature differences. At a molecular level, a moth's muscle is not very different than a human's,
|Contact: Tona Kunz|
DOE/Argonne National Laboratory