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Narrator:Listen to part of a lecture in a Biology class.
獨白:聽下面一段生物學的課程。
Well, it's finally looking like spring is arriving.
嗯，現在看來，春天終于要到來了。
The last of the winter snow would be melting away in a few days.
幾天之后，最后的冬雪將會融化。
So before we close today, I thought I'd mention a biological event that's a part of the transition from winter to spring, something you can go outside and watch if you have some patience.
所以，在我們今天結束課程之前，我想談談一個與冬春換季有關的生物學事例，這個事情你們如果有耐心的話，自己出門兒就能觀察到。
There is a small creature that lives in this area; you've probably seen it.
這個片區內生活著一群小動物—你們很可能已經見過了。
It's the North American wood frog.
名字叫做北美林蛙。
Now the wood frog's not that easy tosspot since it stays pretty to close to the ground, under leaves and things and it blends in really well with its background as you can see.
現在林蛙不是特別好找，因為它們和地面貼得很近，而且藏在樹葉等與它們外形相似、可以掩蓋它們蹤跡的隱蔽物下面。
But they are worth the effort because they do something very unusual, something you might not have even thought possible.
但是，它們值得你們費這番功夫，因為它們有一個非常奇妙的本領，這項本領你們想來絕對不可思議。
OK North American wood frogs live over a very broad territory or range.
好的，北美林蛙生活的地域是非常廣闊的，
They're found all over the northeastern United States and all through Canada and Alaska, even inside the Arctic Circle.
從美國北部一直到加拿大和阿拉斯加甚至到北極圈，你們都能夠看到它的身影。
No other frog is able to live that far and north.
沒有另外一種蛙類可以生活在如此遙遠的北地。
But wherever they live, once the weather starts to turn cold and the temperature starts to drop below freezing, as soon as the frog even touches an ice crystal or a bit of frozen ground, well, it begins to freeze.
但不管它們到底生活在那一個地方，一旦天氣變冷，氣溫達到冰點以下，甚至只要林蛙碰到了一小點冰渣或凍土，它馬上就會被冷凍起來。
Yeah...yes to me. You look a little bit taken aback.
嗯，我覺得是這樣的。你們看上去有點吃驚？
Wait, you mean it's still alive but it freezes, solid?
等一下，您的意思是，它是活著的，但它是冰凍、不動的？
Well, almost. Ice forms in all the spaces outside the cells but never within a cell.
嗯，差不多吧！在林蛙的體內，除了細胞之外的空間里，到處都是冰。
But… then how does its heart beat?
但是…這樣的話，它的心臟怎么跳動呢？
It doesn't.
已經不跳了。
But…then how could it…
但是，那樣它怎么…
You are gonna do such a thing?
你是想知道這是怎么一回事嗎？
Well, that first touch of ice apparently triggers a biological response inside the frog.
嗯，林蛙接觸冰這個動作觸發了林蛙體內的生理反應。
That first of all starts drawing water away from the center of its body, so the middle part of the frog, its internal organs, its heart, lungs, liver, these start getting drier and drier while the water that's being pulled away is forming a puddle around the organs just underneath the skin.
首先，這個反應會導致體腔內脫水，所以，在林蛙的中部，它的內部器官，包括心臟、肺、肝都會變得越來越干燥。
And then that puddle of water starts to freeze.
其后，它的蹼也會脫水結冰。
OK, up to known, the frog's heart is still beating, right? Slower and slower but…and in those last few hours before it freezes, it distributes glucose, a blood sugar throughout its body, its circulatory system, sort of acts like an antifreeze.
好的，到了現在這一步，林蛙的心臟依舊是在跳躍，對吧？越來越慢，對的…到結冰前的幾個小時里，它的體內會釋放葡萄糖這一血糖到全身的循環系統，這種葡萄糖似乎起到的是抗凍劑的作用。
A solution of antifreeze like you put in your car in the winter?
林蛙的這種釋放葡萄糖的這種做法，即像我們在冬季往車里加抗凍劑一樣嗎？
Well, you tell me.
嗯，一會兒我講完了你來告訴我吧！
In frogs, the extra glucose makes it harder for the winter inside the cells to freeze.
在林蛙體內，超量的葡萄糖會使得它們在冬季時細胞內部很難結冰。
So the cells stay just slightly wet, enough so that they can survive the winter.
所以，那時細胞僅僅會濕潤一些，而這個濕度恰恰是保證它們在冬季的生存的程度。
Then after that, the heart stops beating altogether.
等到了那時，心臟的全部機能都會停止。
So is that the same?
所以，你還覺得你的比喻恰當嗎？
I don't really know, but how long does it stay that way?
我真的不知道，不過，這種狀態會持續多久呢？
Well, it could be days or months, all winter in fact but umm, see the heart really doesn't need to do any pumping now because the blood is frozen too.
嗯，長則幾個月，甚至整個冬天，短則幾天。實際上，嗯，因為心臟不需要輸送血液，因為血液也是凝固的。
I just, I guess I just don't see how it isn't, you know, clinically dead.
我想，只是這樣想，我不明白，它這種狀態衛生么還是活著的，因為按照臨床醫學的經驗來說，它已經死了。
Well, that's the amazing thing and how it revives is pretty amazing too.
嗯，那就是它的神奇所在！
After months without a heartbeat, spring time came around again, the earth starts to warm up and suddenly one day, ping, a pulse, followed by another one, then another until maybe ten, twelve hours later, the animal is fully recovered.
并且，它的解凍過程，也是令人吃驚的。在長達數月的心臟停跳期后，春季再次降臨，地球又重新開始溫暖如春，突然某一天，一聲脈搏的顫動之后，接著又來了一個…脈搏恢復了大概 10 到 12 個小時之后，林蛙就徹底恢復了。
And does the thawing process have some kind of trigger as well?
那么這種解凍的過程是否也有一個觸發點呢？
Well, we are not sure actually, the clearer thing is even though the sun is warning the frog up on the outside, its inside thaw out first, the heart and brain and everything.
嗯，我們目前也不清楚。我們可能會想到的是，當溫暖的陽光叫醒青蛙之后，它的軀體內部包括大腦、心臟等會率先恢復。
But somehow it all just happens that way every spring.
但事實上，每次春季的時候，林蛙的身體解凍是一次性到位的。
But after they thaw does it affect them like their lifespan?
但目前還沒有關于其壽命的證據。但是，在解凍之后，這種經歷會影響它的壽命嗎？
Well, hmm, we really don't know a lot about how long a wood frog normally lives, probably just a few years but there is no evidence its longevity. It does have some other impacts though.
嗯，我們現在還沒有研究清楚一只林蛙正常情況下會存活多久，有可能是幾年,但這個過程對林蛙的其他方面倒有一定影響。
In studies, we found that when it comes to reproduction, freezing diminishes the mating performance of males.
一些研究中，我們發現到了繁殖季，有過冰凍經歷的雄性林蛙交配次數會減少。
After they've been frozen and thawed of course, they don't seem quite as vocal.
在他們冰凍—解凍之后，它們鳴叫求偶的欲望并不十分強烈。
They move slower and they seem to have a harder time recognizing a potential mate.
它們跑動得很慢，而且尋找雌性交配對象時會有麻煩。
So if the male frog could manage not to go through this freezing cycle, he'd probably have more success in mating.
所以，如果雄性林蛙能夠設法避免進入冰凍周期的話，它交配的成功率就會大一些。
