Saharan silver ants have evolved special hairs that give their bodies a metallic sheen, helping the species stay cool in hot desert environments, according to a new study.
Led by scientists from the Free University of Brussels, the study shows that these body hairs make the ants almost 10 times more reflective, allowing them to prevent overheating. As the species' name implies, the hairs are a glittery silver color.
Using a Scanning Electron Microscope (SEM), the researchers examined the hairs in great detail and traced the path of incoming light rays. Compared to ants that had been shaved, hairy Saharan silver ants were able to stay up to 35 degrees Fahrenheit cooler under simulated sunlight.
"The ability to reflect solar radiation by mean of total internal reflection is a novel adaptive mechanism in desert animals, which gives an efficient thermal protection against the intense solar radiation," explained Serge Aron, co-author of the study. "To the best of our knowledge, this is also the first time that total internal reflection is shown to determine the color of an organism."
While most Sahara Desert insects and animals come out at night to avoid daytime temperatures, the Saharan silver ant is well-adapted for high temperatures. In fact, shiny worker ants emerge from their nests during the hottest midday period to scavenge corpses of heat-stricken animals, even when temperatures exceed 122 degrees Fahrenheit.
While previous studies have shown that the ants' unique body hairs are responsible for their silvery glow and thermoregulation, it is not until recently that researchers explored the hairs' optical properties.
The high-powered microscope revealed a unique design that gives the hairs total reflectivity. Each hair's triangular cross-section and corrugated surface causes it to act like a prism, with sunlight reflected off the bottom side, thus ensuring the hair doesn't absorb any heat. This mirror effect gives the ant its bright silver sheen and provides effective thermoregulation needed to withstand deadly desert heat.
"By restricting foraging activity to the hottest period of the day, the ants minimize the chances of encountering their most frequent predator - a lizard that ceases all activities when the temperature becomes unbearable," Aron, lead author Quentin Willot and their colleagues wrote.
While most arthropods have cylindrical or plate-like body bristles, these reflective hairs are believed to be unique to this Saharan ant species. What's more is that these desert ants have exceptionally long legs that keep their bodies elevated off the hot surface and allow them to run fast, which, in turn, helps them stay cool through convection.
The study was published in the April 13 issue of the journal PLOS ONE.
