Challenging previous theories, researchers at UC Irvine and Humboldt University propose that insects such as grasshoppers, moths, butterflies, some types of fruit flies, beetles and bugs close off their respiratory systems periodically to keep out excess oxygen, thus preventing damage to their tissues.

Timothy Bradley, professor of ecology and evolutionary biology at UCI, and Stefan Hetz, assistant professor of physiology at Humboldt University, Germany, report their findings in the Feb. 3 issue of Nature.

The insect respiratory system is designed to accommodate occasions when the insect is active. For example, a grasshopper is most active when it flies. When the grasshopper is inactive and resting, however, it continues to breathe in oxygen at the same high volume it uses while flying. The result is excess internal oxygen that can cause oxidative damage -- the destruction of biomaterial due to excess oxygen -- to tissues. To protect their bodies, insects like grasshoppers discontinue breathing.

"We propose that most insects stop breathing in order to lower their internal oxygen concentration to physiologically safe levels, and that they then substantially reduce gas exchange to maintain the oxygen at these safe values," Bradley said. "This hypothesis explains the respiratory pattern of insects in different environments in ways that previous models can't."

Two previous models for explaining why insects punctuate their breathing with periods of closure are (1) such discontinuous breathing reduces water loss and (2) it enables insects to rid their bodies of carbon dioxide, respiration's byproduct, when the insects are underground. As is true for miners, insects, while underground, are faced with high-carb
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Contact: Iqbal Pittalwala
iqbal@uci.edu
949-824-3969
University of California - Irvine
14-Feb-2005