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How Do Chameleons Change Color?

How Do Chameleons Change Color?


There is a misconception about chameleons
that they change their color in order to blend in with their environment. That is actually
not the case. When a chameleon is calm it is green and so it naturally blends in with
its leafy surroundings. But male chameleons change color when they become excited in the
presence of a female or a rival male, as shown here. I will put the first frame in the bottom
right for comparison. As you can see, as he becomes more excited, his color changes to
be more yellow orange and red. So instead of blending in this chameleon will now stand
out. But how do chameleons actually change their color? For years we thought that there
was a simple well-established mechanism for this color change. In their skin, chameleons
have different cells containing colored pigments. Some are yellow others are red and some contain
the dark melanin pigment. Many animals including chameleons are known to turn a darker shade
by causing the melanin to spread out along the fingery extensions of the cell. They turn
lighter again by condensing the pigment back into one spot. It was assumed that chameleons
must turn yellow, orange and red in the same way, by causing those pigments to spread out
in those cells. But new research from collaborating groups of physicist and biologists at the
University of Geneva shows that this is incorrect. Now the first clue should come from the fact
that there is actually no green pigment in the a chameleon. The green color actually
created by two distinct mechanisms, pigment color and structural color. Beneath the yellow
pigment cells, there are cells containing tiny 130 nm crystals regularly arranged in
a lattice. Now light diffracts off these crystals and due to the spacing between them, blue
light constructively interferes and is therefore strongly reflected. Whereas the other colors
are not reflected. This is very similar to how a morpho butterfly wing creates an iridescent
blue. There is no blue pigment just the periodic nanoscale structure that acts as a strong
reflector for only one color. So a chameleon looks green due to the combination of the
yellow light from the pigment plus the blue light reflected off the crystal structure
beneath it. So how do chameleons change this green into yellow orange and red? Well previously
it was assumed that the color change was achieved by dispersing pigments in the colored cells.
But now scientists have found it’s actually the crystals underneath which are changing.
By increasing the spacing between the crystals the chameleons can change which color is selectively
reflected. Bigger gaps between the crystals are better at reflecting longer wavelengths.
So as the spacing increases, the color changes from blue to green to yellow, and then orange
and red. Scientists compared skin samples from calm green chameleons and excited yellow
chameleons and found that indeed, in the excited chameleon the crystal spacing was much further
apart. Here you can see a single cell enlarged and the color it reflects changing from blue
to green to yellow, orange and red. Plus, a computer simulation of the light reflected
off crystals while their spacing is decreasing also provides excellent agreement with these
observations. Furthermore, applying physical pressure to the skin causes the crystals to
compress and so they reflect more blue. When that pressure is removed, the crystals expand
again reflecting more green light. The structure of a chameleon’s skin gets even more fascinating,
as there is another layer of cells underneath which also contain crystals. But these crystals
are larger more spaced out and more disorganized. This means they reflect longer wavelengths
in the infrared part of the spectrum and they reflect a broader range of these wavelengths.
It’s thought that the function of this layer could be to reflect light from the sun since
these chameleons live in bright full-sun habitats. So male chameleons don’t change their color
by spreading out red and yellow pigments. Instead they do something much more remarkable.
They actively tune the spacing between nanoscale crystals in order to create structural colors
that span the whole length of the visible spectrum. Now what I find amazing is that
in this day and age we thought we had the answer to how chameleons change color, but
it actually took the combined expertise of physicists and biologists working together
to figure out what’s really going on. This episode of Veritasium was supported by
Linda.com a leading online learning platform with over 3000 video courses taught by experts
in areas ranging from video production to web development and computer programming.
Chances are if you can think of a topic, they have a course that teaches it. Now as part
of this sponsorship they are offering Veritasium viewers a 10 day free trial of any and all
courses on the site. Just go to Lynda.com/Veritasium or click the link in the description. You
know one of the courses I’m really interested in is Adobe After Effects. That’s a really
good animating software. Right now I still do all of my animations including the ones
in this video in Final Cut Pro which is really tedious and time consuming. Now if you’re
interested in learning how to program maybe you should try out their Java courses. Those
are really good. Or if like me you’ve always wanted to do more with Photoshop, you should
try out one of their Photoshop or photography courses. So if you want to learn something
new today, you should go to Lynda.com/Veritasium for 10 days free trial. There’s really nothing
to lose me. I really want to thank Lynda.com for supporting me, and I want to thank you
for watching.

100 comments on “How Do Chameleons Change Color?

  1. I just found these, thought I should share them with all you Chameleon lovers. Grabbed one for my GF.
    https://bit.ly/2JJMoUp

  2. So the specific structure of those tiny crystals causes them to absorb every color except for blue. While that's fascinating, isn't that exactly the same the red and yellow pigments do with red and yellow light?

  3. great bro…thanks for sharing truth… and i have a request ..could you please explain about your realisation on metaphysics… i am curious and exicted to know from you… !!

  4. Not all chameleons have a green resting state. Different locales and species of chameleon have different resting colors and patterns.

  5. That's so much cooler than pigments imo, it's like every chameleon has a million little tunable microwave cavities under their skin, except for visible light (I know, that's not the same exact mechanism).

  6. I hope they didn't hurt too many chamelonies (name for childhood pet – was an anole, tho) getting skin samples and such.

  7. Hi. First time I comment on your videos, so let me say I really like your channel.
    As a scientist, I find that a lot of youtube content falls way too short on communicating science in an accurate and accessible way, but your videos really accomplish that. Everytime I watch one, I learn something new.
    I am a photophysicist and I deal with colors all the time, so I really enjoyed this clip.
    I just want to leave a small correction. The green color cannot be created by the combination of yellow pigment and reflected blue light. This is something that I find hard to explain to colleagues and friends that do not usually work with optical materials, but pigment color and light color are not the same, and actually, they are complementary (opposite). Light has 3 primary colors, Red/Green/Blue (RGB), and pigments have Cyan/Magenta/Yellow. For a pigment to be yellow, it will have to absorb blue light, and reflect Red+Green. Thus, the Yellow pigment would absorb the blue light reflected by the nanocrystal layer, or, otherwise, the color would be white. To yield green, the nanocrystals should reflect green, and the pigment contribution should be minimal. If the information on that study is written as you explained here, it should not be correct.

    Keep up the good work
    Cheers

  8. Chameleons change their color due to their energy in motion.It is automatic to cover up when it's life is in danger.He have the red green blue and they mix together depends the excitement mode.Every living thing have that defense ,but only barn owls can detect it.Humans change their color as well ,example when angry they change to red ,pink normal. fear yellow ,sick pale etc.all lives are like that.

  9. It is really incredible how our discoveries become more accurate when different branches of science blend together… Just loved the video… #keepasking

  10. I can give a explanation:
    Bragg's law 2dsinθ=nλ

    As distance between atoms(d) increases wavelength(λ) also increases. Since they are directly proportional.

  11. If they reflect colour that means that they are unable to change colour if it is dark . Am I right or can some one explain me ?

  12. How do the chameleons consciously color match? That's the part that gets me. It's like how an octopus consciously knows how to change its color and form to match another object. The sentient aspect is what really amazes me

  13. of course, physicist and biologist and don't forget mathematicians working together can solve all illnesses and diseases and can discover all the miraculous science and engineering of the life sciences.

  14. How does the chameleons "sense" the color of the objects they touch? I've seen they replicating the colors of different surfaces.

  15. How could anyone think God didnt make this and this was just another beautiful complex thing made by some massive explosion billions of years ago in outer space billions and billions of light years away. Wake up

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