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Chameleon Colors Reflect Their Emotions

When light hits a chameleon's skin, the cells appear different colors depending on the mood of the animal.

Panther chameleon
Furcifer pardalis
Chameleons can quickly change their appearance in response to temperature, environment, and mood. Scientists recently identified a key factor in their ability to do this: The lizards can “tune” the distances between nanoscale crystals in their skin that reflect light, creating a spectrum of colors.
Skin Formed by Layers of Cells
Structure
Cells
Crystals
How Skin Changes Color
Submissive
Neutral
Excited
Manuel Canales and Daniela Santamarina, ngm staff; Meg Roosevelt. art: Shizuka Aoki
sources: Devi Stuart-Fox; Russel Ligon; Kristopher Karsten; Michel C. Milinkovitch, Jeremie Teyssier, Suzanne V. Saenko, Dirk van der Marel (INSET PHOTOS)

Scientists have long thought that chameleons change color when skin cell pigments spread out along veinlike cell extensions.

But Michel Milinkovitch, an evolutionary geneticist and biophysicist, says that theory didn’t wash—there are many green chameleons but no green pigments in their skin cells.

So Milinkovitch and his University of Geneva colleagues began “doing physics and biology together,” he says.

Beneath a layer of pigmentary skin cells, they found another layer of skin cells containing nanoscale crystals arranged in a triangular lattice. (Also see "Amazing Pictures: Baby Chameleon Doesn't Know It Hatched.")

By exposing samples of chameleon skin to pressure and chemicals, the researchers discovered that these crystals can be “tuned” to alter the spacing between them. That in turn affects the color of light that the lattice of crystals reflects.

As the distance between the crystals increases, the reflected colors shift from blue to green to yellow to orange to red—a kaleidoscopic display that’s common among some panther chameleons as they progress from relaxed to agitated or amorous.

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