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Entomology

Golden Years
Cockroaches suffer from creaky joints too

You've probably never pondered the aging process of the cockroach. You've never looked at a cockroach and thought: That one's a little long in the tooth. Or: That one must be looking for the early bird special. No, you've thought: Where'd I put the Raid?

But a creature we find repulsive in ordinary life may help us solve some of the mysteries of human aging. Is getting old primarily a mechanical problem, a decrepitude in joints and muscles? Or is it a bigger problem located somewhere in our worn-out brains?

Roaches are good research subjects because they're big by insect standards, which makes it easy to study their relatively simple nervous systems. They don't require a lot of care either. You can chuck them in a plastic garbage bin, slather Vaseline around the rim to discourage escapes, toss them some dog food once in a while, and everyone's happy.

There are reasons roaches have been around for more than 300 million years. One is that they're fabulous at running away from danger. Although even the swiftest roaches only go three miles (four kilometers) an hour, that's all the velocity they need to sprint to the nearest crack in the baseboard.

Christopher Comer, a neuroscientist at the University of Illinois at Chicago, studies roach escape behavior. "When you puff wind on a cockroach, it's off and running in 50 milliseconds," Comer says. "If you smack a roach's antenna abruptly, it can turn and run in 15 to 20 milliseconds. Quicker than the blink of an eye." Compare that with a human, whose brain usually needs about 200 milliseconds (a fifth of a second) to respond to a stimulus.

But roaches, like all of us, get old. Angela Ridgel of Case Western Reserve University recently shot high-speed video images (125 frames per second) as roaches ran down a little hallway with a see-through floor. Ridgel discovered that about 60 weeks after its final molting, a roach starts to trip. The front legs literally snag on the middle legs. Old roaches also begin to slip while walking uphill.

Studies of escape behavior by Comer and Ridgel show another sign of roach senescence: When they get older, roaches react less reliably to being touched or hit by a puff of wind. Sometimes they run; sometimes they just stand there.

In addition to aiding in the study of human aging, roach research can help the space program, Comer says. He points out that the roach escape mechanism has an admirable redundancy. The hairs on a roach's cerci, two rear appendages extending from the abdomen, are tied into one sensory system, but the antennae are tied into another. So the roach can operate with one system deactivated. In some experiments researchers remove the insect's head, and it still manages to get around.

"Suppose you wanted to build controlling circuitry for a rover on Mars," Comer says. "You might want to base the design on the kind of dual circuitry that insects use. With a simple nervous system roaches achieve rather sophisticated control."

And if the rover breaks down, the engineers could blame it on a bug in the system.

—Joel Achenbach
    Washington Post staff writer

Web Links

Insect Nervous System
www.cals.ncsu.edu/course/ent425/tutorial/nerves.html#2 
Read simple descriptions and see anatomical diagrams of the various parts of an insect's nervous system.

Neuroscience for Kids
faculty.washington.edu/chudler/neurok.html
Don't be fooled by the title, this site is a good introduction to the nervous system for all ages.

Featured Creatures
creatures.ifas.ufl.edu/index.htm
Get information on the biology and behavior of hundreds of insects, including many species of cockroaches.

More Articles by Joel Achenbach
www.washingtonpost.com/wp-dyn/style/columns/achenbach/
Read some of writer Joel Achenbach's columns for the Washington Post.


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Bibliography

Gordon, David George. The Compleat Cockroach: A Comprehensive Guide to the Most Despised (and Least Understood) Creature on Earth. Ten Speed Press, 1996.
 
Ridgel, Angela, Roy Ritzmann, and Paul Schaefer. "Effects of Aging on Behavior and Leg Kinematics During Locomotion in Two Species of Cockroach." Journal of Experimental Biology (December 15, 2003), 4453-65. Available online at www.cwru.edu/artsci/biol/Ridgel%20article.pdf.
 
Schaefer, Paul, and Roy Ritzmann. "Descending Influences on Escape Behavior and Motor Pattern in the Cockroach." Journal of Neurobiology (Vol. 49, 2001), 9-28. Available online at www.cwru.edu/artsci/biol/Schaefer%20and%20Ritzmann%20v49%20p9.pdf.




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