英语听力文摘 English Digest 731 麋鹿眼睛为何可以变色？

Reindeer¹ Eyes

Rudolph the reindeer is best known for his brightly colored red nose. For other reindeer, however, the most colorful thing about them is actually their eyes. Researchers have found that depending on the season, the eyes of Arctic reindeer change from gold to blue.

Tapetum Lucidum

Like many mammals, Arctic reindeer have a structure in the eye called the tapetum lucidum, TL for short. It sits behind the retina and reflects light back to increase the sensitivity of night vision. The TL is also responsible for reindeer eye color changes.

During the Arctic summer, when it’s always light outside, reindeer TL is gold — a color that reflects more light back through the retina, better enabling reindeer to see in daylight. (This is why, by the way, many mammals have gold colored eyes.)

When Darkness Reigns²

But when the Arctic winter sets in and darkness reigns, the TL turns blue. The result of this is less light reflecting back out through the retina, making it easier for the animals to see predators³ in dim conditions.

The color change may be caused by shifting pressure in reindeer eyes, which stems from constant pupil dilation⁴. When compressed, the TL reflects shorter wavelengths⁵ of blue light which are more plentiful⁶ during Arctic winters.

驯鹿鲁道夫以其鲜艳的红色鼻子而闻名。然而，对于其他驯鹿来说，它们最多彩的地方其实是它们的眼睛。研究人员发现，根据季节的不同，北极驯鹿的眼睛会从金色变为蓝色。

透明绒毡

和许多哺乳动物一样，北极驯鹿的眼睛有一种叫做绒毡层灵芝的结构，简称TL。它位于视网膜后面，反射光线以增加夜视的灵敏度。TL还负责驯鹿眼睛颜色的变化。

在北极夏季，当外面总是很亮的时候，驯鹿的TL是金色的，这种颜色可以通过视网膜反射更多的光线，从而更好地让驯鹿在白天看到东西。（顺便说一句，这就是为什么许多哺乳动物都有金色的眼睛。）

当黑暗降临

但当北极的冬天来临，黑暗笼罩时，TL就会变成蓝色。这样做的结果是，通过视网膜反射回来的光线减少，使得动物在昏暗的环境中更容易看到捕食者。

这种颜色的变化可能是由于驯鹿眼睛的压力变化引起的，这是由于瞳孔不断扩大造成的。压缩后，TL反射的蓝光波长更短，在北极冬季更为充足。

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

5 wavelengths   

n.波长( wavelength的名词复数 )；具有相同的/不同的思路；合拍；不合拍

参考例句：

• I find him difficult to talk to—we're on completely different wavelengths. 我没法和他谈话，因为我们俩完全不对路。 来自《简明英汉词典》
• Sunlight consists of different wavelengths of radiation. 阳光由几种不同波长的射线组成。 来自辞典例句

6 plentiful   

adj.富裕的，丰富的

参考例句：

• Their family has a plentiful harvest this year.他们家今年又丰收了。
• Rainfall is plentiful in the area.这个地区雨量充足。