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变色龙是如何改变颜色的?

How Do Chameleons Change Color?

我们对变色龙有一个误解,他们改变自身的颜色
There is a misconception about chameleons that they change their color in order to blend
是为了与环境融为一体。实际情况并非如此。当一只变色龙平静时
in with their environment. That is actually not the case. When a chameleon is calm it
它是绿色的,因此自然地与茂密的环境相融合。但是当雄性变色龙
is green and so it naturally blends in with its leafy surroundings. But male chameleons
面对雌性或雄性竞争对手变得兴奋而改变颜色,如图所示
change color when they become excited in the presence of a female or a rival male, as shown
我会把第一张画面放在右下角作比较。正如你所看到的
here. I will put the first frame in the bottom right for comparison. As you can see, as he
随着他越来越兴奋,他的颜色变得有更多黄橙色和红色
becomes more excited, his color changes to be more yellow orange and red. So instead
因此变色龙现在将变得显眼而不是融入。但变色龙如何变色呢?
of blending in this chameleon will now stand out. But how do chameleons actually change
多年来,我们认为对变色存在一个简单的完善的机制
their color? For years we thought that there was a simple well-established mechanism for
在他们的皮肤里,变色龙有不同的含有色素的细胞。
this color change. In their skin, chameleons have different cells containing colored pigments.
有些是黄色的,有些是红色的,有些包含黑色素。许多动物包括
Some are yellow others are red and some contain the dark melanin pigment. Many animals including
变色龙通过让黑色素沿着指状细胞分散使其变暗
chameleons are known to turn a darker shade by causing the melanin to spread out along
再通过压缩黑色素成一点使其变亮
the fingery extensions of the cell. They turn lighter again by condensing the pigment back
假设变色龙变黄、变橙、变红必须用同样的方式
into one spot. It was assumed that chameleons must turn yellow, orange and red in the same
即通过这些色素分散在这些细胞中。但是来自
way, by causing those pigments to spread out in those cells. But new research from collaborating
日内瓦大学的物理学家和生物学家联合组的新研究表明 这是不正确的
groups of physicist and biologists at the University of Geneva shows that this is incorrect.
现在第一个线索应该来自这样一个事实,在变色龙体内是没有绿色素的
Now the first clue should come from the fact that there is actually no green pigment in
绿色是由两种不同的机制制造的,即颜料色和结构色
the a chameleon. The green color actually created by two distinct mechanisms, pigment
在黄色色素细胞下面,一些细胞包含有
color and structural color. Beneath the yellow pigment cells, there are cells containing
微小的130纳米晶体规则排列成一个晶格。现在光在这些晶体中衍射
tiny 130 nm crystals regularly arranged in a lattice. Now light diffracts off these crystals
由于它们之间的间距,蓝光发生干涉而因此受到强烈反射
and due to the spacing between them, blue light constructively interferes and is therefore
但是其他颜色没有被反射
strongly reflected. Whereas the other colors are not reflected. This is very similar to
这和大闪蝶翅膀如何产生一种绚烂的蓝色非常相似,不存在蓝色色素
how a morpho butterfly wing creates an iridescent blue. There is no blue pigment just the periodic
只是周期性纳米结构作为对唯一颜色的一个强烈的反射物
nanoscale structure that acts as a strong reflector for only one color. So a chameleon
所以一只变色龙的绿色是由来自色素的黄光加上其下的晶体结构反射的蓝光
looks green due to the combination of the yellow light from the pigment plus the blue
那么,变色龙是如何从绿色变成黄橙色和红色的?
light reflected off the crystal structure beneath it. So how do chameleons change this
以前认为它变色是
green into yellow orange and red? Well previously it was assumed that the color change was achieved
通过分散色素进入这些色彩细胞。但现在科学家发现实际上是
by dispersing pigments in the colored cells. But now scientists have found it’s actually
下面的晶体改变。通过增加晶体之间的间距
the crystals underneath which are changing. By increasing the spacing between the crystals
变色龙可以有选择地反射何种颜色来改变。晶体之间更大的的缝隙
the chameleons can change which color is selectively reflected. Bigger gaps between the crystals
善于反射更长的波长。所以随着间距的增加,颜色变化
are better at reflecting longer wavelengths. So as the spacing increases, the color changes
由蓝色变为绿色,到黄色,然后是橙色和红色
from blue to green to yellow, and then orange and red. Scientists compared skin samples
科学家比较了平静的绿色变色龙和兴奋的黄色变色龙皮肤样品
from calm green chameleons and excited yellow chameleons and found that indeed, in the excited
发现的确在兴奋变色龙中,晶体间隔远得多。在这里你可以看到一个放大的细胞
chameleon the crystal spacing was much further apart. Here you can see a single cell enlarged
它反射的颜色从蓝色到绿色,再到黄色,然后橙色和红色。另外
and the color it reflects changing from blue to green to yellow, orange and red. Plus,
计算机所模拟的随着晶体间距的减少,光线反射的结果
a computer simulation of the light reflected off crystals while their spacing is decreasing
与这些观察结果一致。此外,通过对皮肤施加
also provides excellent agreement with these observations. Furthermore, applying physical
物理压力而导致晶体压缩,所以他们反射更多的蓝色。
pressure to the skin causes the crystals to compress and so they reflect more blue. When
当压力被移除,晶体再次扩大反射更多的绿光
that pressure is removed, the crystals expand again reflecting more green light. The structure
变色龙的皮肤结构变得更迷人,并且下面还有一层细胞
of a chameleon’s skin gets even more fascinating, as there is another layer of cells underneath
也包含晶体。但这些晶体体积更大,间隔更宽,且排列紊乱
which also contain crystals. But these crystals are larger more spaced out and more disorganized.
这意味着它们反射光谱中波长更长的红外部分并且它们
This means they reflect longer wavelengths in the infrared part of the spectrum and they
反射了更宽范围内的这些波长。人们认为这一层的功能
reflect a broader range of these wavelengths. It’s thought that the function of this layer
可能是反射来自太阳的光线,因为这些变色龙生活在明亮的阳光充足的栖息地
could be to reflect light from the sun since these chameleons live in bright full-sun habitats.
所以雄性变色龙不是通过分散红色和黄色色素来改变它们的颜色
So male chameleons don’t change their color by spreading out red and yellow pigments.
相反,他们做一些更显著的事。为了产生能跨越整个可见光谱的结构色
Instead they do something much more remarkable. They actively tune the spacing between nanoscale
他们积极地调整纳米级晶体之间的间距
crystals in order to create structural colors that span the whole length of the visible
现在我觉得神奇的是,在这个时代
spectrum. Now what I find amazing is that in this day and age we thought we had the
我们认为我们能回答变色龙如何变色。但实际上它需要
answer to how chameleons change color, but it actually took the combined expertise of
物理学家和生物学家的综合专业知识,共同努力找出到底发生了什么
physicists and biologists working together to figure out what’s really going on.
Veritasium的这一集由Linda.com支持。这是一个领先的在线学习平台
This episode of Veritasium was supported by Linda.com a leading online learning platform
超过3000个视频课程,从视频制作到
with over 3000 video courses taught by experts in areas ranging from video production to
web开发和计算机编程领域等专业领域。如果你能想到一个话题,他们
web development and computer programming. Chances are if you can think of a topic, they
都有一个教授的课程。现在作为这个赞助的一部分,他们提供Veritasium的观众
have a course that teaches it. Now as part of this sponsorship they are offering Veritasium
一个10天免费试用所有课程。只需去Lynda.com/Veritasium网站
viewers a 10 day free trial of any and all courses on the site. Just go to Lynda.com/Veritasium
或点击描述中的链接。你知道我真正感兴趣的课程之一就是
or click the link in the description. You know one of the courses I’m really interested
Adobe After Effects。这是一个很好的动画软件。
in is Adobe After Effects. That’s a really good animating software. Right now I still
现在我仍然通过Final Cut Pro(软件名)制作我所有的动画,包括这个视频中的那些
do all of my animations including the ones in this video in Final Cut Pro which is really
这真的很繁琐和费时。现在如果你有兴趣学习如何编程
tedious and time consuming. Now if you’re interested in learning how to program maybe
或许你应该尝试他们的Java课程。这些都是很好的。如果你一直喜欢我
you should try out their Java courses. Those are really good. Or if like me you’ve always
想用Photoshop做更多的事情,你应该尝试他们一个Photoshop或摄影课程
wanted to do more with Photoshop, you should try out one of their Photoshop or photography
如果你今天想学习新东西,你应该去Lynda.com/Veritasium网站
courses. So if you want to learn something new today, you should go to Lynda.com/Veritasium
免费试用10天。这真的没什么损失。我真的要感谢Lynda.com支持我
for 10 days free trial. There’s really nothing to lose. I really want to thank Lynda.com
我感谢您的收看
for supporting me, and I want to thank you for watching.

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