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Silver Ants Stay Cool Using Special Hairs

Jun 18, 2015 10:24 PM EDT
silver ant
Pictured: Silver ant optical macro with two panels: Left: Sahara silver ants forage in the midday sun and look like droplets of mercury rolling on the desert surface. Right: The silvery appearance is created by a dense array of uniquely shaped hairs.
(Photo : Norman Nan Shi and Nanfang Yu, Columbia Engineering)

It can get pretty hot in the Sahara desert, one of the hottest terrestrial environments on Earth, so to stay cool silver ants use special hairs to survive, new research shows.

A team from Columbia University, along with colleagues from the University of Zürich and the University of Washington, is the first to demonstrate that the unique structure and organization of the ants' hair allow the creatures to control a wide range of the solar spectrum and keep cool.

"This is a telling example of how evolution has triggered the adaptation of physical attributes to accomplish a physiological task and ensure survival, in this case to prevent Sahara silver ants from getting overheated," lead study author Nanfang Yu, assistant professor of applied physics at Columbia Engineering, said in a statement.

And they sure need all the help they can get. Saharan silver ants (Cataglyphis bombycina) by no means have an easy life. In order to avoid predators, they have to forage for food during the hottest time of the day (midday) - when surface temperatures reach up to 158 degrees Fahrenheit (70 degrees C). That temperature is near fatal. Ants have to keep their body temperature below 128.48 F (53.6 C) otherwise they will die.

Researchers have long wondered how these tiny insects manage to survive under such thermally extreme and stressful conditions.

Well, it turns out it's all in the hairs. Using electron microscopy and ion beam milling, Yu's team discovered that silver ants are covered on the top and sides of their bodies with a coating of uniquely shaped hairs with triangular cross-sections that keep them cool in two ways. One, is that these hairs are highly reflective under the visible and near-infrared light. But the hair coating doesn't just help keep these solar waves away.

In addition, the hairs also act as an antireflection layer in the mid-infrared solar spectrum range, which allows the ants to emit excess internal heat off their bodies and into the cooler air around them.

"We quickly realized these two effects are actually helping each other," Yu told The Washington Post. "The combination of this tool leads to the optimum cooling effect."

Together, these two effects help reduce an ant's body temperature by up to 50 degrees Fahrenheit (up to 10 C), according to the study.

"The fact that these silver ants can manipulate electromagnetic waves over such a broad range of spectrum shows us just how complex the function of these seemingly simple biological organs of an insect can be," researcher Norman Nan Shi noted in the statement.

Researchers are currently working to find ways of taking this unique cooling system and applying it to "metasurfaces" with optimal cooling properties.

The findings were published in the journal Science.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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