Chameleons don't change color to match their environment; it’s just the opposite. How do they do it? By manipulating tiny crystals in their skin. Now, UC Berkeley researchers are on a quest to create synthetic chameleon skin inspired by these reptiles’ uncanny ability.

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How do Chameleons Change Color?

Chameleons are some of the most brilliantly colored animals on the planet. But how did they evolve the ability to change color?

Scientists used to believe that chameleons changed color by spreading out pigments in their skin, much like octopuses or squid do.

The top layer of chameleon skin – called the epidermis – contains yellow pigment cells called xanthophores, and red pigment cells called erythrophores. But the amount of pigment in the cells stays the same, even when the chameleon changes color.

Just beneath the chameleon’s skin is a layer of cells called iridophores. These cells contain microscopic salt crystals, which are arranged in a threedimensional pattern like oranges stacked on a fruit stand.

When light hits the crystals, some wavelengths are absorbed and some are reflected. The result, to our eyes, is the beautiful rainbow of colors on the chameleon’s skin. But what we’re actually seeing is light that is bouncing off of these tiny crystals. What we perceive as green, for example, is blue wavelengths of light being reflected off the crystals and through the layer of yellow xanthophore cells in the chameleon’s epidermis. The result is bright green skin that contains no green pigment!

The process of changing color is called metachrosis.

Why do Chameleons Change Color?

Chameleons don’t change color to match their environment. In fact, it’s just the opposite.

Their baseline is camouflage.

When chameleons are relaxed, they’re mostly green. They naturally blend into their home in the forest canopy. They even mimic leaves by dancing around a little.

But when they feel threatened, annoyed, or just want to show a little swagger, that’s when their color changes.

Scientists once thought that chameleons colorchanging abilities allowed them to better camouflage themselves. Most species of chameleons live high in the forest canopy and their various shades of green provide natural camouflage. Even their movement provides camouflage – they dance around to mimic leaves blowing in the wind.

In fact, chameleons change color primarily to communicate with each other, as though they were living mood rings. Males will warn each other about their territory and females will change color to let males know whether they’re interested in breeding.

Chameleons also have a second layer of iridiophore cells just beneath the first. The crystals in that layer are larger and reflect light waves in the infrared wavelengths. This suggests that chameleons are also changing colors to regulate their temperature, according to Milinkovitch. Chameleons are coldblooded and heat their bodies with the warmth of the sun.

Read the article for this video on KQED Science:
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