X-RAYS SHOW BUGS CAN BREATHE LIKE HUMANS
23 January 2005 - University of Chicago

"We're using one of the biggest scientific instruments in the world to look at one of the tiniest animals, and we're finding out new things about the most diverse animal group on Earth," researcher Mark Westneat, zoologist and evolutionary biomechanist at the Field Museum of Natural History in Chicago, told United Press International.

The new technique the scientists employed to peer inside living animals promises to reveal the hidden inner workings of organisms, shedding X-ray light for discoveries that benefit everything from human health to robotics.

"Right now we're not at the stage of putting a warm and fuzzy creature in there," Westneat said. "But it would work, and it would be really neat for anatomical studies on model animals like mice. You could have a high-definition video of a heart beating, look at how the wall of the artery changes thickness during pumping."

Earlier attempts to see movements inside living insects were not powerful enough to make out fine details at high resolution, since they were too small to image properly. Scientists at Argonne National Laboratory in Illinois solved the problem by harnessing their synchrotron, a circular particle accelerator more than 1,000 feet wide that accelerates electrons to nearly the speed of light, a process that generates some of the most powerful X-ray beams in the world.

Once the beams pass through their target, they travel about 18 inches and hit a scintillator crystal where the X-rays are transformed into recordable visible light.

"The images are so precise, they've reconstructed the positions of all the grains in a sand pile," Westneat said.

Physicist Wah-Keat Lee at Argonne tried using the method on a dead ant, revealing incredibly detailed images of the ant's internal organs. After searching online for a biologist who might be interested, he sent Westneat a still image.

"I got very excited. As soon as I saw this, I asked, 'Could we do real-time images, can live animals survive the beam?" Westneat said.

In the journal Science, the researchers and colleagues in Germany present their findings in living ants, beetles, crickets, butterflies, cockroaches and dragonflies captured from the woods near the lab.

"We used real high-tech. We just used scotch tape to mount the insects on slides," Westneat said.

Insects do not have lungs, instead possessing a system of tubes called trachea. Scientists beforehand thought insects exchanged oxygen slowly and passively.

"We saw all these tubes that were much less dense, and said, 'They're full of air, must be the tracheal system,'" Westneat recollected. "Then we saw all these tubes squeezing and expanding, and we said, 'What the hell is that?'"

The astonished scientists discovered insects could breathe in a way much like how humans inflate and deflate their lungs. Using rapid cycles of expansion and compression, wood beetles, house crickets and carpenter ants could exchange up to 50 percent of the air in their main tracheal tubes every second, a ventilation rate similar to that of a person during moderate exercise.

"The idea that one could get high resolution X-ray movies, not stills, of the trachea in an ant would have been laughable just a few years ago," said invertebrate zoologist Michael LaBarbera of the University of Chicago, who called the experiment a "technical tour de force."

A better understanding of insect respiration could help pesticide design. Such findings also could cast a whole new light on insect evolution and capabilities.

"It's a bit early to say in that we don't yet know precisely how this behavior fits into the physiology of insects," LaBarbera told UPI. "However, anytime you have to revise your picture of the basic physiology of the most diverse group of organisms on the planet, you can be sure that the ramifications are going to be widespread."

This method has a number of limitations. It only works on very small animals, with a maximum 6 by 8 millimeter window. The X-rays also are lethal, although insects can survive for 15 to 20 minutes inside.

While others might suggest such breathing behavior in the examined insects might be an artifact of their peculiar circumstances, "we had insects eating normally in there," Westneat said. His team hopes to use more natural mounting procedures in the future, such as anesthesia.

These findings were accidentally discovered when the researchers were examining mouthpart movements, and they are continuing research along that avenue. They also hope to study wing hinge movements, which Westneat said could help robotic design. They also hope to study shrimps, ticks, spiders and fish in future, although they are uncertain if the imaging will work with water.

Similarly large synchrotrons are found in France and Japan, with smaller synchrotrons found globally. Westneat hopes to develop a user group for biologists to use the device for study.

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