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If you have a pet, one of your jobs might be to make sure your pet has plenty of food and water...
如果你有一只宠物，那么你的一个工作可能就是确保它有充足的食物和水...
unless, of course, your pet is a fish!
除非，你的宠物是一条鱼！
You have to feed your fish, but you don't have to give them water, there's water all around them!
你必须给它们喂食，但不必给它们水喝，因为它们周围全是水。
But do fish need to drink that water? Well, some fish do, but some don't!
但鱼需要喝水吗？有些鱼需要，有些则不需要。
It all depends on where they live.
这完全取决于它们生活在哪儿。
You probably already know that your body needs water for lots of reasons!
你可能知道了你的身体因为各种原因需要水分！
It's so important, in fact, that different parts of your body work together to make sure that there's about the same amount of water inside of it at all times.
它非常重要，事实上，你身体的不同部位共同协作以确保体内水量在任何时候都保持同一水平。
If the amount of water gets too low, you get thirsty, and you grab a drink.
如果体内水量太低的话，你会感觉口渴，然后就去喝水。
And if the amount of water gets too high, you get rid of the extra when you pee.
如果体内水量太高的话，你就会小便排出多余的水分。
Well, fish also need to keep the right amount of water on the inside of their bodies.
同样的，鱼类也需要在体内保持适量的水分。
And the water outside of a fish's body can affect whether that fish needs to drink water or not.
鱼体外的水会影响鱼是否需要喝水。
Most fish live in one of two kinds of water.
大多数鱼生活在一种或两种水域。
Some fish, called freshwater fish, live in places where there's no salt in the water, like lakes, ponds, and rivers.
有些鱼被称为淡水鱼，它们生活的水域不含盐，如湖泊、池塘和河流。
Other fish, called saltwater fish, live in water that has lots of salt in it, like the ocean.
其他的鱼被称为咸水鱼，它们生活的水域含很多盐，如海洋。
Freshwater fish have an easier time keeping the right amount of water inside of their bodies.
淡水鱼更容易保持体内水分充足。
That's because water enters into a freshwater fish's body right through its gills.
这是因为水通过鱼鳃直接进入淡水鱼体内。
Gills are the body parts that fish use to breathe.
鱼鳃是鱼类用来呼吸的身体部位。
Fish breathe by pulling water into their mouths, then pushing the water over their gills and out of their body.
鱼的呼吸方式是先把水吸进嘴里，然后再通过鱼鳃把水排出体外。
And in freshwater fish, gills also end up taking in some of the water, and the fish ends up with more water in its body.
淡水鱼是鱼鳃吸收一些水，它体内的水量就会增多。
So freshwater fish don't really have to drink water through their mouths like we do.
所以它们不必像我们一样用嘴喝水。
These fish actually have to make sure they don't get too much water,
这些鱼要确保它们不吸收太多水分，
and their body has to work very hard to get rid of the extra water as waste.
它们的身体必须非常努力才能把多余的水处理掉。
While freshwater fish get a lot of water in through their gills...saltwater fish lose a lot of water through their gills.
淡水鱼通过鱼鳃获得大量水分，而咸水鱼却通过鳃失去大量水分。
As water flows over a saltwater fish's gills,
当水流过咸水鱼的鱼鳃时，
the salt that's in the water outside of the fish's body sucks out some of the water that's inside of the fish's body through its gills.
鱼体外水中的盐通过鱼鳃吸出一部分鱼体内的水。
Since water is always moving over a fish's gills, that means water is always leaving a saltwater fish's body.
因为水分总是通过鱼鳃流动，这就意味着水分总是离开咸水鱼的身体。
And that means that the fish that live in saltwater need to drink a lot.
这就需要咸水鱼喝大量的水。
Most animals can't drink salt water when they're thirsty, but these fish can!
大部分动物口渴时不能喝盐水，但这些鱼却可以！
They gulp and swallow water almost constantly.
他们几乎经常大口吞水。
Saltwater fish have a special system in their bodies that takes salt and puts it back out into the ocean…and everything stays in balance!
咸水鱼体内有一个特殊的系统能吸出盐分，并把它放回海洋中...万物都保持着平衡呢！
So, some fish need to drink water, and some don't...it just depends on where they live!
所以，一些鱼喝水，一些鱼不喝水，这取决于它们生活的地方。
Thanks for joining us here on SciShow Kids! Do you have a question for us here at the Fort?
感谢您收看本期的儿童科学秀！您对我们沃斯堡有什么疑问吗？
Grab a grownup and leave a comment down below, or send us an email to Kids@scishow.com!
找个大人在下方留言或发邮件至Kids@scishow.com！
Thanks, and we'll see you next time, here the Fort!
感谢您的收看！我们下期见！沃斯堡等你哦!
