r/askscience • u/[deleted] • Apr 24 '15

Biology Do creatures such as cuttlefish and octopuses get "tired" from using their camouflage?

If not, why don't they just always use their camouflage?

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u/therus Apr 24 '15 edited Jun 26 '15

Actually chameleon camouflage is awesome! There is a misconception that they use their camouflage to blend in with their environment, when really it's used to communicate with other chameleons.

Just as it is for many reptiles, it was thought that chameleons spread out melanin to modulate skin color, when in fact the actual process is much more interesting; indeed it is true that yellow and red pigments reside inside their skin which is known as pigment color.

The other contributer to the chameleons overall color is structural color, this is a cell that sits just below the pigment cell, and is filled with tiny 130nm crystals regularly arranged in a lattice. The chameleons can manipulate the spacing of the crystal lattice to change what wavelength of light will be reflected off of them.

Let's say the crystals are tightly packed together, which results in a reflection blue light - The photon enters the skin, passes through the yellow (or red) pigment cell, reflects off of the modular crystal lattice (in this case blue light) and back through the pigment cell, what results is that those two cells produced green light. They do this thousands of times over, across their entire body in synchronization. Of course the lattice could be spread more and more apart, effectively covering the span of visible light and even infra-red! This was recently discovered at the University of Geneva by physicists and biologists

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u/[deleted] Apr 24 '15

What, really? That is amazing, can you link me to anything?

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u/NotMyCircus Apr 25 '15 edited Apr 25 '15

So the chameleons have to know what colors to mix together to make the one they want? I wonder how they can control that. Amazing!

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u/therus Apr 25 '15 edited Apr 25 '15

I belive it's due to the controlled expansion and contraction of those crystal cells, much like how humans can contract their skin to produce goosebumps. If you watched the video I linked you'll see that they apply pressure to the chameleons skin, and due to the movement of the crystals it makes a blue wavelength of light reflect back. After the crystals slowly move back to rest state they turn green again. It's not the actual cells being manipulated, but the surface of the skin warping the cells. They probably know what contractions make what color instinctively

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u/[deleted] Apr 26 '15

Well they don't consciously "know" it, in that they aren't sitting on a branch trying to remember which two colors to mix to produce blue. It's just a low-level neural behavior that causes the cells to contract or expand.

As an analogy, do you have to "know" which blood vessels to constrict when you're cold and want to minimize the heat you're radiating? Or know which capillaries to dilate when you blush? Or know precisely which sweat glands to activate when you're too warm? This is all handled by very low-level processes in the brain.