Courtesy of Shaun Roberts

Rather than rely solely on passive diffusion, insects use discontinuous patterns of gas exchange to avoid the toxic effects of oxygen, according to researchers at the University of California, Irvine. The peculiar type of breathing exhibited by some insects is a cyclical pattern of opening and closing the spiracles, the apertures that connect the respiratory tracheal system with the exterior.1

"Two main hypotheses have been proposed to explain discontinuous breathing," says senior author and UCI evolutionary biologist Timothy Bradley. One suggests that closing the spiracles reduces respiratory water loss, he explains. The other suggests that the discontinuous breathing pattern may have evolved initially in underground insects as a means of better excreting carbon dioxide.

Bradley and coauthor Stefan Hetz found that oxygen levels within the trachea of the moth Attacus atlas remain constantly low at a range of ambient oxygen concentrations. "Our hypothesis is that,...

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