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Oh, hey guys, you caught us on our lunch break!
嘿，朋友们，你正好赶上了我们的午餐时间
Squeaks and I just stepped out of the lab to have a little snack...
我和Squeaks刚刚溜出了实验室去买小零食，
Well, at least, I'm having a snack.
好吧，至少我正吃着。
And since Squeaks doesn't have to eat like I do, I was just explaining to him what teeth are for.
由于Squeaks不必像我一样吃东西，所以我刚才正向它解释牙齿的作用。
People have different kinds of teeth.
人有好几种不同的牙齿。
I have molars in the back of my mouth that help me grind up vegetables and other things.
我口腔最里面的牙齿叫臼齿，它能帮我磨碎蔬菜和其他东西。
But I also have pointed canine teeth so I can tear through things like meat.
但我也有尖尖的犬齿帮我撕碎肉类等食物。
Being able to eat different kinds of food is really important, to help you stay healthy.
吃不同种类的食物很重要，这关乎你的健康。
Other animals have different kinds of teeth, too.
其他动物也有不同种类的牙齿。
But while they're all super-useful, some of them can seem a little strange.
有些尽管看起来有些奇怪的牙齿却超级有用。
Like, we all know sharks have sharp teeth.
比如，我们都知道鲨鱼有尖锐的牙齿。
But did you know many sharks have 5 rows of teeth? Sometimes even more!
但是你知道许多鲨鱼有五排牙齿吗？有时甚至更多。
A shark can go through thousands of teeth in a lifetime!
鲨鱼一生会替换数千颗牙齿!
That's because, unlike us, shark's teeth aren't rooted in bone.
那是因为鲨鱼的牙齿不像我们人类那样扎根在骨头里。
Instead, their jaws are made of something softer, called cartilage—that's the same flexible stuff that you have
相反，鲨鱼的下颌是由柔韧的软骨组成的。
in your ears, or in the tip of your nose.
和我们人类耳朵和鼻尖处的软骨一样。
Since shark's teeth sit in this soft cartilage, they can lose them pretty easily—especially considering how they eat!
由于鲨鱼的牙齿是从软骨中长出来的，所以很容易脱落，尤其是当它们进食的时候!
Sharks feed by biting down hard on their prey—like seals, or other fish—
鲨鱼捕猎时会狠狠地咬住它们的猎物，如海豹或其他鱼类，
and they shake them from side to side with a lot of force.
然后非常使劲儿地左右摇晃嘴里的猎物。
This can make their teeth come loose or even fall out, so they need to be able to replace them easily.
这会导致它们的牙齿松散甚至脱落，所以它们需要简单地替换牙齿。
Luckily for them, they have these rows of new teeth right behind the last ones, just waiting to move up.
幸运的是，这些新牙齿就在脱落的位置，等待长长。
When a shark loses a tooth, it's replaced with another one in just one or two days.
鲨鱼只需要一两天就能长出新牙。
Other predators have different kinds of teeth for catching food.
其他捕食者用于捕食的牙齿种类不同。
Vipers, for example, are a kind of snake, and they have fangs.
例如，毒蛇——蛇类的一种，就拥有毒牙
When a snake is resting, these special teeth fold up inside its mouth, so that they're out of the way.
平时，这些毒牙收缩在上颚，这样就不会影响它们的正常活动
But when the snake bites its prey, like, say, a rat—
但是，当毒蛇撕咬猎物如老鼠时，
Oh, no, no, no, not you, Squeaks! No a mechanical one, a real one!
稍安勿躁，Squeaks,不是吃你这种机械老鼠，是真真正正的老鼠哦
When it bites into a real rat, these teeth act like needles.
当毒蛇咬住老鼠时，毒牙就像针一样刺入老鼠体内，
Toxic venom then travels from the snake's mouth through the hollow fangs and directly into the prey.
毒囊里的毒液通过其中空的毒牙直接注入到猎物体内
But teeth aren't just for eating! Other animals use them for different reasons.
但是，牙齿不仅仅用来捕食。 其他动物的牙齿就有与众不同的作用
For instance, did you know tusks are teeth?
比如 你知道獠牙吗
Walruses have tusks up to a meter long, and they keep growing throughout their whole life.
海象的獠牙可以长到一米长， 而且一生都在生长。
Male walruses sometimes use their tusks like swords, to fight with other males.
雄性海象有时会把它们的獠牙用作武器，来和其他雄性搏斗。
But, both males and females use their tusks for other reasons, too.
但是，雄性和雌性海象的獠牙都可以用作它途。
Like, when they're swimming under the ice,
例如，当它们在冰下游泳时，
they can use them to poke holes in the ice so they can come to the surface to breathe.
它们可以用獠牙在冰上捅一个洞，方便它们浮出水面换气。
And they can even use their tusks to pull their big, heavy bodies out of the water.
它们甚至利用其獠牙将自己笨重的身体从水里拉出来。
But there's probably one animal that's more famous than any other for its unusual teeth.
但是，也许有一种动物因其特殊的牙齿而更加出名。
That's right! That's right! I'm talking about beavers!
是的，我说的就是海狸。
Beavers are well-known for their oversized incisors.
海狸因其超大的门牙而闻名于世。
These teeth never stop growing, so beavers are constantly trying to wear them down by chewing on wood.
它们的门牙一直在长，因此，它需要通过啃木头不停地磨牙。
You might think that chewing on wood all of the time would ruin the beavers' teeth.
你也许会想，不停地啃咬木头会损坏海狸的牙齿，
But the front side of their teeth actually has iron in it!
但是，海狸的牙齿正面其实是有铁存在的。
Iron is the same stuff that they use to make really strong metals.
这种铁与我们铸造坚硬材料的铁相同。
And it not only makes beavers' teeth extra tough,
它不仅让海狸的牙齿变得坚硬无比,
it also gives them their unique, rusty orange color, kind of like the rust you might see on an old car or bicycle.
还让海狸拥有了独一无二的铁锈色牙齿，有点儿像旧汽车或旧自行车上见到的铁锈的颜色。
So it's this extra strength that makes it possible for beavers to bite through wood, for as long as they want to.
正是这种坚固才使得海狸随心所欲地不停啃木头。
No wonder they can stay so busy, those busy beavers!
怪不得它们总是那么忙碌，忙碌的海狸啊。
Speaking of busy, we have to get back to work, but thanks for sharing our lunch time with us!
说到忙碌，我们得回去工作了，谢谢各位和我们一起度过午餐时间。
