Guanine nanocrystals the secret to chameleon's changing colors

Previous studies suggest chameleons that can change colors faster and display more vivid combinations are more successful in finding mates.

By Brooks Hays
A chameleon in a relaxed state, feature blues and greens. Photo by Poreddy Sagar/CC
A chameleon in a relaxed state, feature blues and greens. Photo by Poreddy Sagar/CC

GENEVA, Switzerland, March 10 (UPI) -- In addition to the manipulation of pigmentation, scientists have discovered that chameleons rapidly change their colorful costumes by shifting the position of light-reflecting cells in the layers of their skin.

According to a new study by researchers at the University of Geneva, in Switzerland, the cells get their reflective abilities via tiny embedded crystals called guanine nanocrystals.


These crystals are vital to a variety of chameleon species who use color changes as part of complex social signaling routines, such as interaction with a potential mate.

"These colours are generated without pigments," lead study author Michel Milinkovitch, a professor of genetics and evolution at the University of Geneva, told The Guardian.

By shifting the angles and positioning of these two cell layers -- featuring different cells with different sized crystals -- the chameleons can change how light is reflected and refracted, thus augmenting their coloration.

"When the skin is in the relaxed state, the nanocrystals in the iridophore cells are very close to each other -- hence, the cells specifically reflect short wavelengths, such as blue," Milinkovitch explained to Live Science.


Conversely, when they're moved slightly farther apart, the cells reflect longer wavelength colors like yellow, orange or red.

Researchers studied the crystal-boasting cells with high-resolution videography, allowing scientists to build computer models that predicted how their arrangement would reflect light.

The study was published this week in the journal Nature Communications.

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