Short-sheeted.
Evolution has shaped how desert dung beetles keep water from escaping through their breath--but not in the way previously thought. Using an elaborate contraption, researchers have discovered that whereas many insects draw air in one set of holes (or spiracles) and out another, one kind of dung beetle uses a single hole to breathe.
To study the respiratory habits of these desert sanitation engineers, which roll the dung of behemoth herbivores, scientists at the University of the Witwatersrand in South Africa developed a rubber skirting device to separate body compartments and measure the oxygen and carbon dioxide flowing through individual spiracles. Clad in a latex sheet, with sampling tubes superglued over each spiracle, the beetles "look ready for takeoff," says entomologist Marcus Byrne, who reports his results in the 15 August issue of the Journal of Experimental Biology with co-author Frances Duncan.
The authors say the findings poke holes in the prevailing theory of how these critters conserve water. Scientists had assumed that dung beetles inhaled through the mesothoracic spiracles in front and exhaled through abdominal spiracles in back, into a sealed cavity that buffers the holes from the arid air. But Byrne and Duncan found that resting beetles breathe through a single spiracle on the right side of the thorax. With only one hole, they theorize, air spends more time in the beetle's body, helping it conserve water.
