听力文摘：驯鹿的秘密（在线收听）

Rudolph the reindeer is best known for his brightly colored rednose.

鲁道夫驯鹿最大的特征就是红彤彤的鼻子。

For other reindeer, however, the most colorful thingabout them is actually their eyes.

然而，其他驯鹿身上最”出彩”的地方，则是他们的眼睛。

Researchers have found thatdepending on the season, the eyes of Arctic reindeer change from gold to blue.

研究人员发现，随着季节的转变，北极地区驯鹿的眼睛会从金色变为蓝色。

Like many mammals, Arctic reindeer have a structure in the eye called the tapetum lucidum, TL forshort.

同许多哺乳动物一样，北极地区驯鹿的眼睛里有一个叫做反光膜的组织，简称TL。

It sits behind the retina and reflects light back to increase the sensitivity of night vision.

它位于视网膜后，其功能是反射光线，以增强眼睛夜间视物的敏感性。

麋鹿眼睛.jpg

The TL is also responsible for reindeer eye color changes.

驯鹿的眼睛会变色就是因为反光膜。

During the Arctic summer, when it's always light outside, reindeer TL is gold-a color that reflectsmore light back through the retina, better enabling reindeer to see in daylight.

北极夏季会出现极昼现象，阳光无时无处不在，此时驯鹿眼中的反光膜呈金色，这种颜色可反射更多透过视网膜的光线，使驯鹿在白昼时的视物性更好。

(This is why, by theway, many mammals have gold colored eyes.)

（顺便说一句，这也是为什么许多哺乳类动物的眼睛是金色。）

But when the Arctic winter sets in and darkness reigns, the TL turns blue.

但当北极的冬季来临，出现极夜现像，黑暗笼罩大地时，驯鹿眼中的反光膜会变成蓝色。

The result of this is lesslight reflecting back out through the retina, making it easier for the animals to see predators in dim conditions.

此时，透过视网膜，反射出去的光会减少，对于动物来说，这样可以使他们在光线不佳的情况下，更容易看见猎物。

The color change may be caused by shifting pressure in reindeer eyes, which stems from constantpupil dilation.

驯鹿的眼睛会变色可能是驯鹿眼睛受到的压力发生改变所致，压力源自瞳孔不断放大。

When compressed, the TL reflects shorter wave lengths of blue light which are moreplentiful during Arctic winters.

反光膜在受到压迫时会反射较短波长的蓝光，这种光在北极的冬天到处都是。