The study, "No giants today: tracheal oxygen supply to the legs limits beetle size,'' will be presented Oct. 10 and 11 at Comparative Physiology 2006: Integrating Diversity. The conference will be held Oct. 8-11 in Virginia Beach. The research was carried out by Alexander Kaiser and Michael C. Quinlan of Midwestern University, Glendale, Arizona; J. Jake Socha and Wah-Keat Lee, Argonne National Laboratory, Argonne, IL; and Jaco Klok and Jon F. Harrison, Arizona State University, Tempe, AZ. Harrison is the principal investigator.
The Paleozoic period, about 300 million years ago, was a time of huge and abundant plant life and rather large insects -- dragonflies had two-and-a-half-foot wing spans, for example. The air's oxygen content was 35% during this period, compared to the 21% we breathe now, Kaiser said. Researchers have speculated that the higher oxygen concentration allowed insects to grow much bigger.
Tubes carry oxygen
First, a bit of background: Insects don't breathe like we do and don't use blood to transport oxygen. They take in oxygen and expel carbon dioxide through holes in their bodies called spiracles. These holes connect to branching and interconnecting tubes, called tracheae, Kaiser explained.
Whereas humans have one trachea, insects have a whole tracheal system that transports oxygen to all areas of their bodies and removes carbon dioxide. As the insect grows, tracheal tubes get longer to reach central tissue, and get wider or more numerous to meet the additional oxygen demands of a larger body.
Insects can limit oxygen flow by closing their
Source:American Physiological Society