听力文摘：驯鹿的秘密

Rudolph the reindeer¹ 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 reigns², 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 predators³ 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 dilation⁴.

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。

1 reindeer   

n.驯鹿

参考例句：

• The herd of reindeer was being trailed by a pack of wolves.那群驯鹿被一只狼群寻踪追赶上来。
• The life of the Reindeer men was a frontier life.驯鹿时代人的生活是一种边区生活。

2 reigns   

n.君主的统治( reign的名词复数 )；君主统治时期；任期；当政期

参考例句：

• In these valleys night reigns. 夜色笼罩着那些山谷。 来自《现代汉英综合大词典》
• The Queen of Britain reigns, but she does not rule or govern. 英国女王是国家元首，但不治国事。 来自辞典例句

3 predators   

n.食肉动物( predator的名词复数 )；奴役他人者（尤指在财务或性关系方面）

参考例句：

• birds and their earthbound predators 鸟和地面上捕食它们的动物
• The eyes of predators are highly sensitive to the slightest movement. 捕食性动物的眼睛能感觉到最细小的动静。 来自《简明英汉词典》

4 dilation   

n.膨胀，扩张，扩大

参考例句：

• Time dilation works both ways. 时间膨胀在两方面都起作用。 来自辞典例句
• The ciliary body is an anterior dilation of the choroid at the level of the lens. 晶状体是脉络膜石晶状体平面上向前扩大的部分。 来自辞典例句