color is a rarity in the animal world, and also a mystery, until now!

Hey everybody thank you for watching DNews today. I'm Trace and I am right here on our

brand new set!

Chameleons change color so well, and are so well known across the planet for doing so,

that their name is synonymous with someone who is good at changing their look, behavior

or opinions as their situation changes. Most people think chameleons change color for camouflage,

but that's not it at all! Only the males can change color, and they do so to communicate

danger to other nearby chameleons, or for a mating display. Ladies. *wink*

It's a pretty dramatic show when a chameleon swaps its green for bright red, and thanks

to new research, we now know HOW they do it. Researchers from the University of Geneva

looked at the skin cells of chameleons to observe how they change color. Within their

skin, it turns out, chameleons have cells called iridophores. Suspended within those

cells are tiny guanine nanocrystals which are formed into a lattice. When relaxed, the

chameleons’ iridophore lattices are contracted, and mainly reflect blue light, but when excited

the chameleon expands and three dimensional lattices expand along with them, reflecting

different wavelengths of light! Below that layer, there's a layer of skin with even larger

nanocrystals which reflect near-infrared light; providing "passive thermal protection." Which

is great, because these cold-blooded animals can't change their body temperature; changing

that base layer may be one way they can affect how much near-infrared light, and therefore

heat, is absorbed into their body,.

Camouflage is also called cryptic coloration; or a color and pattern that makes an animal

difficult to discern from its surroundings; concealing it. The ability to CHANGE colors

isn't unique to chameleons -- some fish, frogs, insects, crustaceans, cephalopods, and other

lizards can do it too, but they don't have nanocrystals… this research is the first

time that's been seen in reptiles. And other animals use different methods of color shifting.

Cuttlefish, for example, can also change their colors at will; but rather than crystal-filled

iridophores, they use chromatophores. Chromatophores are sacs of a single pigment of color surrounded

by muscle. The cuttlefish has learned to widen or constrict that sac to show more or less

of that color. Invertebrates like cephalopods use these chromatophores too, and for more

on that you can check out our video exploring how the disco clam can reflect light like

a disco ball!

Over time, evolution, mutation and simply breeding with others can cause changes in

the colors of species, humans included -- all blue-eyed humans descend from a single mutated

ancestor. Usually because those animals which have these colorful adaptations tend to survive

better. Zebra stripes confuse predatory eyes, helping to disguise individuals and making

the herd look more massive; background matching camouflage helps both predators like tigers

blend with their environment; as well as helping their prey hide by resembling it's surroundings…

but these adaptations take many generations to develop! Active color change is pretty

rare in the Animal Kingdom. Before this research, scientists believed chameleons changed color

the same as cuttlefish or octopuses, but once they put the skin cells into a super-magnifying

electron microscope, they were able to see this unique and super cool system for reflecting

light!

How do you think humans camouflage into our surroundings? Do we? Why or why not...