Chameleons are some of the most fascinating creatures on the planet, and they only get more fascinating when you examine them using an electron microscope. That’s what a group of scientists at the University of Geneva just finished doing. Their goal was to definitively determine how chameleons change the color of their skin, and they think they’ve got a pretty clear picture.
It turns out that it’s not pigment that makes the magic happen. It’s tiny crystal mirrors (called iridophores, a type of chromatophore) embedded in a chameleon’s skin that allow it to alter its appearance. When relaxed, the iridophores in a chameleon’s skin are packed together tightly. When it becomes excited, they spread out. The movement of these tiny “selective mirrors” affects how light is reflected off the chameleon’s skin, and the end result is that an observer sees different colors. Smaller gaps between the crystals produce blues and greens; wider ones yield oranges and reds.
Chameleon’s aren’t the only creatures with iridophores in their skin, but they are the only ones that split them into two layers. The upper layer, which has a somewhat regular cellular arrangement, reflects light in the visible spectrum. The lower one has a more haphazard layout, and it helps chameleons reflect near-infrared frequencies and regulate their body temperature.
That trait isn’t unique to chameleons either, but again, they appear to be the only reptile that sports both systems. The Geneva team isn’t ready to make the final call just yet, though. They’re going to perform more experiments to confirm that the second layer really is a sort of a passive cooling setup.
Image courtesy Wikipedia
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