Chameleons Modify Nanocrystals Under Their Skin to Change Color

Tuesday, 10 March 2015 - 4:20PM
Nanotechnology
Tuesday, 10 March 2015 - 4:20PM
Chameleons Modify Nanocrystals Under Their Skin to Change Color

One of nature's most spectacular mysteries has finally been solved, as scientists have determined the mechanism by which chameleons change the color of their skin. According to a new study published in Nature Communications, chameleons abruptly change color by manipulating a layer of nanocrystals under their skin.

 

When male chameleons begin to display, usually when they've encountered a competitive male or receptive female, they immediately change color, transforming their blues to white, their background color to yellow, and their greens to reds within minutes of seeing the other chameleon. Researchers had previously discovered that the creatures were able to perform certain, less drastic, transformations by expelling and absorbing melanin into cells. They could use this mechanism when turning from light to dark green, for example, but scientists were unable to explain how chameleons were able to dramatically change from green to red.

 

Now, the research team from the University of Geneva has found that the animals have at least one layer of cells called iridiphores, which in turn contain tiny crystals made of guanine, underneath their skin, and that they change color from green to red by modifying the spacing between these crystals. Under normal circumstances, the nanocrystals are arranged in a dense lattice, which causes them to reflect blue wavelengths most strongly. But when the lattice is contracted or expanded, they are able to reflect different wavelengths of light.

 

"They're basically pulling apart or squashing together the lattice," said lead author Michel Milinkovitch to The Guardian.

 

Colour change and iridophore types in panther chameleons:

Chameleons

 

[Credit: Nature Communications]

 

The researchers found that when the chameleons get excited, they expand the lattice by as much as 30%, allowing the crystals to reflect more yellow and red wavelengths. They were also able to replicate their results when they removed a layer of skin from the chameleons and exposed it to chemicals that induced the same change in arrangement.

 

"We observed exactly the same change of color in the dish," Milinkovitch told BBC. "It really demonstrates that the colour change is happening due to the modification of these crystals."

 

Iridophore types in lizards and function of D-iridophores in chameleons:

Chameleons

[Credit: Nature Communications]

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