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Rudolph the reindeer is best known for his brightly colored rednose.
魯道夫馴鹿最大的特征就是紅彤彤的鼻子。
For other reindeer, however, the most colorful thingabout them is actually their eyes.
然而，其他馴鹿身上最”出彩”的地方，則是他們的眼睛。
Researchers have found thatdepending on the season, the eyes of Arctic reindeer change from gold to blue.
研究人員發現，隨著季節的轉變，北極地區馴鹿的眼睛會從金色變為藍色。
Like many mammals, Arctic reindeer have a structure in the eye called the tapetum lucidum, TL forshort.
同許多哺乳動物一樣，北極地區馴鹿的眼睛里有一個叫做反光膜的組織，簡稱TL。
It sits behind the retina and reflects light back to increase the sensitivity of night vision.
它位于視網膜后，其功能是反射光線，以增強眼睛夜間視物的敏感性。
The TL is also responsible for reindeer eye color changes.
馴鹿的眼睛會變色就是因為反光膜。
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.
北極夏季會出現極晝現象，陽光無時無處不在，此時馴鹿眼中的反光膜呈金色，這種顏色可反射更多透過視網膜的光線，使馴鹿在白晝時的視物性更好。
(This is why, by theway, many mammals have gold colored eyes.)
（順便說一句，這也是為什么許多哺乳類動物的眼睛是金色。）
But when the Arctic winter sets in and darkness reigns, the TL turns blue.
但當北極的冬季來臨，出現極夜現像，黑暗籠罩大地時，馴鹿眼中的反光膜會變成藍色。
The result of this is lesslight reflecting back out through the retina, making it easier for the animals to see predators in dim conditions.
此時，透過視網膜，反射出去的光會減少，對于動物來說，這樣可以使他們在光線不佳的情況下，更容易看見獵物。
The color change may be caused by shifting pressure in reindeer eyes, which stems from constantpupil dilation.
馴鹿的眼睛會變色可能是馴鹿眼睛受到的壓力發生改變所致，壓力源自瞳孔不斷放大。
When compressed, the TL reflects shorter wave lengths of blue light which are moreplentiful during Arctic winters.
反光膜在受到壓迫時會反射較短波長的藍光，這種光在北極的冬天到處都是。
