A bugs life in a bubble

By Folio Staff

Hundreds of insect species live mainly underwater, but how do they breathe? Morris Flynn, a mechanical engineering professor, has completed a study to find out how these species are able to remain underwater without drowning.

Turns out, many bugs create their own waterproof bubbles to help them breathe.

According to Flynn, the rough, waxy surfaces of insects and spiders are water-repellent. In some species, water-repellency is so pronounced that creatures may survive underwater for indefinite periods. This is achieved by an air bubble called a plastron that the insect traps between its body and its hairs, creating an external lung. This lung facilitates oxygen and carbon dioxide exchange with the surrounding water.

“The bubbles will appear as soon as the insect dives into the water, and these long, waxy hairs work almost like Velcro,” Flynn said. “The closer together the hairs, the more pressure the bubble can withstand before collapsing.”

Flynn and his colleagues at MIT in Massachusetts found these insects cannot survive in water where the pressure results in bubble rupture, nor can they survive in shallow water where the bubble surface area is too small.

“We were surprised by the fact that, in some cases, bugs may be unable to survive in shallow water. But we did discover they can safely dive as deep as 30 metres.”

Flynn did this research with a colleague while he was at MIT. He is now continuing his work in the department of mechanical engineering at the University of Alberta.

“This research really appealed to be because there’s a lot of room for some nice interdisciplinary work. 

“Our study combined some aspects of biology, chemistry and hydrodynamics,” said Flynn.

“The project was really multifaceted.”

And while the bubble method might not be adaptable for use for humans, there are still some interesting possible applications, he says.

“We has some grand ambitions of designing a scuba suit that would use many of these same ideas, but the problem is we’re big animals and warm-blooded, which means that the metabolic rate is too high to make that a practical technology for humans,” said Flynn. “But we could apply these ideas to underwater robots. These robots need oxygen for their fuel cells and usually the oxygen is just sent down with them in separate canisters.”

But, says Flynn, it may be possible to fit the robots with a water-repellent surface, “similar to that of these insects, and extract all the oxygen they need from the surrounding water.”

This research appears in the August 10 issue of the Journal of Fluid Mechanics.