Quantum physicists and evolutionary biologists working together have discovered that chameleons change colors by shifting the spacing of tiny crystals in their skin. Their "iridophores," or color-producing skin cells, contain crystals arranged in neat, regular patterns; thus, rather than using pigment to create color, the spacing of the crystals selectively reflect light of certain wavelengths to make "structural colors." By altering how far apart or close together the crystals are-- which is a function of excitement-- chameleons can reflect different wavelengths of light.
However, dig further beneath the surface and the picture is even cooler... literally. Beneath their finely tuned crystal lattice, chameleons have a "cooling" layer of larger, more chaotically arranged cells. That sort of "higgledy-piggledy" structure reflects infrared light, thus keeping out the sun's warming rays.
Expert Dr. Devi Stuart-Fox notes that "what is really novel about this study is that it shows that there are two layers of these iridophores, not just one. And the crystals in the deeper layer affect not just visible colour but also how the skin reflects the near-infrared - a part of the spectrum of sunlight that neither we nor chameleons can see."
Many thanks to Rachel Woodlee for sending along this colorful article!
Swiss researchers have discovered how chameleons accomplish their vivid colour changes: they rearrange the crystals inside specialised skin cells. It was previously suggested that the reptiles' famous ability came from gathering or dispersing coloured pigments inside different cells. But the new results put it down to a "selective mirror" made of crystals.