Scientists have known for some time that insects breathe using a system of internal respiratory tubes called tracheae. Simple mechanisms like diffusion were thought to enable oxygen exchange. But the new work, carried out by a team of scientists from the Field Museum in Chicago and Argonne National Laboratory, shows that in a number of species, respiration can also occur via a mechanism more akin to mammalian lung ventilation: the creatures were observed to pump their respiratory tubes much as humans expand and contract their lungs. And it's all caught on film.
Team member Wah-Keat Lee of Argonne has spent the past several years developing imaging technologies that use the light emitted by the labs Advanced Photon Source a giant high-energy particle accelerator called a synchrotron. The images produced rely on an intense x-ray beam capable of producing not only still images, but also real-time video. On a whim, Lee stuck a dead ant under an intense x-ray beam and observed detailed images of the ant's insides. He then began to search for biologists who might be interesting in teaming up with him and found Mark Westneat, a zoologist at the Field Museum who studies evolutionary biomechanics. Their work, published today in the journal Science, is the first to merge real-time synchrotron x-ray imaging with the study of living things. "I had a hunch that if the right biologists saw this they would be very excited," Lee recalls.
Using the synchrotron, the scientists examined the inner workings of beetles, crickets, ants and other insects with x-rays more than a billion times as intense as those traditionally used to image broken bones in humans. Contraction of the tracheae, the x-ray movies revealed, expelled as much as 50 percent of the air volume at a time, depending on the species of insect.
"This technique can be used on anything that has an organ or process one centimeter or smaller," Westneat says, "and the possibilities are endless." Videos of insect joint motion could be useful in robotics, and Lee is honing the imaging technique to record up to 1000 frames a second (as opposed to the 30 frames a second achieved in the insect films). Westneat envisions future medical studies in which, for example, mice with heart defects could be observed to gain a better understanding of cardiovascular disease. "Any advance in microscopic imaging technology," he remarks, "will eventually be used in medicine."