Hairy Insects Use Bubble "Lungs" to Stay Underwater

Sara Goudarzi
for National Geographic News
August 13, 2008

Of the hundreds of insect species that rely on air bubbles to dive underwater, some can use the bubbles like external lungs to stay submerged for long periods, according to new research that describes how insects manage the feat.

Scientists have known since the 19th century that when aquatic insects dive underwater, they trap an air layer similar to a thin bubble around their bodies and use this air supply to breathe.

The new study is the first to describe exactly how the insects' air layers work, said Steven Vogel, a biology professor at Duke University who was not involved with the paper.

"You might say, with only mild hyperbole, that our understanding [of the bubbles] is now complete," Vogel said.

Hairy Problem

When aquatic insects dive, the layer of air forms between their waxy body surfaces and their rough covering of hairs.

The bubble is held to their hairs by surface tension, the same force that allows a leaf to float on a pool of water.

(Related: "Hairy Legs Help Bugs Walk on Water" [November 3, 2004].)

Air pressure inside the bubble is less than that of the surrounding water, allowing oxygen to flow into the air layer and then into the insect's body via spiracles—small openings that ultimately connect to its bloodstream.

For some insects, gases are exchanged across the bubble's surface, with oxygen being absorbed from the surrounding water while carbon dioxide is expelled.

Such a system allows the bugs to submerge indefinitely, said study co-author Morris Flynn of the University of Alberta.

Continued on Next Page >>




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