 |
|
X-rays
shot through this wood beetle revealed an unknown insect breathing
mechanism. |
Living insects reveal breathing mechanism |
|
Scientists from The Field Museum in Chicago and Argonne, using Advanced Photon Source (APS) X-ray beams, discovered a surprising new insect breathing mechanism that is similar to lung ventilation in vertebrates. “The discovery of this fundamental aspect of respiratory biology for insects could revolutionize the field of insect physiology,” said Mark Westneat, associate curator of zoology at The Field Museum. Insects—the most numerous and diverse group of animals—don’t have lungs. Instead, they have a system of internal tubes called tracheae that are known to exchange oxygen through slow, passive mechanisms, including diffusion. But this new study demonstrates that beetles, crickets, ants, butterflies, cockroaches, dragonflies and other insects also breathe through the use of rapid cycles of tracheal compression and expansion in their head and thorax. Tracheal compression was not found for all types of insects studied, but for those where it was found, the compression patterns varied within individuals and between species. The three species most closely studied—the wood beetle, house cricket and carpenter ant—exchange up to 50 percent of the air in their main tracheal tubes approximately every second. This is similar to the air exchange of a person doing moderate exercise. Until now, it has not been possible to see such movement inside living insects. This problem has been solved by using the brilliant X-rays at the APS to obtain videos of living, breathing insects. “This is the first time anyone has applied this technology to obtain highly detailed, real-time video images of the internal organs of living insects,” said Argonne physicist Wah-Keat Lee. One aspect of the technique that makes the videos so revealing is edge enhancement, which highlights the edges of some internal organs. This effect is due to the special properties of the APS’s X-ray beams. “It’s almost as if parts of the anatomy have been outlined in pencil, like a drawing in a coloring book,” Lee explained. This work may lead to powerful new techniques for studying how living animals function, he added. Indeed, Westneat, Lee and their collaborators are already aiming the synchrotron at the jaws of insects to see how they chew. “Most of the 12 moving parts in an insect’s jaw mechanism are internal, so our inability to see inside living, moving insects has prevented us from understanding how these parts work together,” Lee said. Westneat envisions using similar videos to study animal functions, biomechanics and movements. New discoveries about animal function can have broad implications. For example, active tracheal breathing in the head and thorax among insects may have played an important role in the evolution of terrestrial locomotion and flight in insects, and be a prerequisite for oxygen delivery to complex sensory systems and the brain. This research could not only help scientists learn more about the animals studied but could also provide insights into human health. For example, studying how larval fish move their backbones could shed light on how to treat spinal cord injuries in humans. Likewise, studying the walls of blood vessels in mice and the tiny hearts in beetles—each beetle has eight to ten hearts—could shed light on high blood pressure. “Basic principles of mammal, fish or insect physiology and function could have important implications for health care,” Westneat says. “We intend to develop this novel technique for a range of applications that will greatly improve our knowledge of how tiny animals live and function.” For more information, please contact Catherine Foster. |