Spring 2003 — vol. 21, no. 1 logos home page Contact the logos editor Argonne home page Feature articles Ice smoothie gives heart attacks the 'Big Chill,' may save lives Cadmium causes calcium loss in bones within hours of exposure X-rays penetrate secrets of diesel engine Argonne Update Insect breathing mechanism discovered Surface disorder is more than skin deep Portable detector finds concealed nuclear weapons Gammasphere returns to Argonne

Insect breathing mechanism discovered

A surprising new insect breathing mechanism similar to lung ventilation in vertebrates has been discovered by scientists at Chicago's Field Museum and Argonne.

The discovery of this fundamental aspect of respiratory biology for insects could "revolutionize the field of insect physiology," says Mark Westneat, associate curator of zoology at The Field Museum.

BEETLE BREATH — Researchers shined an X-ray beam through the head and thorax of this wood beetle, Platynus decentis, to view the compression and expansion of tracheal tubes. They discovered that insects breathe rapidly in a manner similar to lungs. Tracheal tubes are visible at the junction between the head and thorax. Photograph: Mark Westneat, courtesy of 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 exchange oxygen through slow, passive mechanisms, including diffusion. But this study demonstrates that beetles, crickets, ants, butterflies, cockroaches, dragonflies and other insects also use rapid cycles of tracheal compression and expansion in their head and thorax to breathe.

The results of the research, performed at the Advanced Photon Source (APS) at Argonne, have been published in the journal Science.

For insects where tracheal compression was found, 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, similar to the air exchange of a person doing moderate exercise.

Up until now, it has not been possible to see movement inside living insects. By using the APS, which produces the most brilliant X-rays in the Western Hemisphere, videos of living, breathing insects were made.

"This is the first time anyone has applied this technology to study living insects," says co-author Wah-Keat Lee, a physicist at Argonne. Scientists using the APS can now precisely analyze structures that once baffled researchers.

Using a phase-enhanced imaging technique, Lee placed a dead ant in the path of the X-ray beam and was amazed to see incredibly detailed images of the ant's internal organs. He searched the Internet for a biologist who might be interested, and he and Field Museum scientists have been working together ever since.

This work opens up the possibility of developing a powerful new technique for studying how living animals function, Lee explains.

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, the authors say.

This would not only help scientists learn more about the animals studied but also provide insights on human health. For example, studying how larval fish move their backbones could shed light on how to treat spinal chord injuries in humans. — Catherine Foster

For more information, please contact Catherine Foster (312-252-5580 or cfoster@anl.gov) at Argonne.