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鱼会小便吗

Do Fish Pee?

感谢Stream Curiosity对PBS Digital Studios的支持
Thanks to curiosity stream for supporting PBS Digital Studios
嘿聪明人 我是乔
Hey smart people, Joe here.
有没有听过那个说法“像鱼儿一样喝水?”
Have you ever heard the phrase “to drinklike a fish?” Well,
除非你是住在海洋里的物种
unless you’re a ocean dwelling species,
才有可能意味着保持清醒
that probably means staying sober.
因为淡水鱼并不喝水!
Because freshwater fish don’t drink!
那么海水鱼呢?
Saltwater fish on the other hand?
它们经常喝水
They’re constantly drinking.
但如果一些鱼总是在喝水而另一些鱼则不喝水
But if some fish drink all the time and other fish don’t drink at all,
我们自然而然地就会问到: 鱼会尿尿吗?
we’re left with an obvious question: Do fish pee?
什么?你从来没想过这个问题?!
What… you’ve never wondered that?!
我们都知道水是生命之源
Water is essential to life as we know it.
为了保证它们的正常的代谢
To keep their chemistry running smoothly,
生物体内需要足够的水
living things need just the right amount of water in their bodies.
你可能觉得鱼不费吹灰之力就能做到这点
You’d think that fish have it made when it comes to staying hydrated,
但事实并非这么简单
but it’s not so easy.
鱼鳃将氧气摄入体内
Fish gills lets oxygen flow into their bodies,
但同时也让水不断地流出去
but they’re also letting water constantly escape.
而海水比鱼身体里的水分要“咸”得多
Ocean water is *saltier* than the insidesof fish.
所以鱼身体里的水会向外流以达到平衡
So water wants to move from the inside out to balance that out.
若你是鱼 而且想活命的话
That’s a problem if you’re a fish
那问题就来了
who wants to stay alive.
这个过程叫做渗透作用
It’s a process called osmosis,
我们可以用鸡蛋来演示
and we can demonstrate that with these eggs.
我已将这些蛋的蛋壳溶解了
I’ve dissolved the shells away,
只剩下蛋膜 它可以让水通过
leaving a membrane that’ll allow water to pass through.
一个鸡蛋放进纯净水里
One is covered in pure H2O.
另一个则放在糖浆里
And one goes into sugar syrup.
糖浆含有很多糖分子 水不是很多
The syrup contains lots of sugar molecules,and not much water,
所以鸡蛋里的水会流出以达平衡
so water passes out of the egg to balance it out,
鸡蛋就缩水了!
and the egg shrinks!
生命在于平衡
Life is all about balance.
即体内平衡
HOMEOSTASIS
我们通过肾脏排出多余的盐和溶解的化学物质
Now, we keep the salts and dissolved chemicals in our blood balanced
以及在口渴时喝水补充体内水份
by flushing the extra through our kidneys,
从而保持身体水盐平衡
and drinking fresh water when we’re thirsty.
但是海水鱼只有一种选择:
But ocean fish only have one option:
它们只能喝海水以满足生存所需
drink salt water in order to get the H2O they need to stay alive.
而且大多数都会喝很多
And most of them do that a *lot*.
但他们需要在不脱水的情况下去除盐
But they need to get rid of the salt without dehydrating,
这时鳃部的特殊细胞会发挥作用
which they do using special cells
将多余的盐排出
in the gills that pump out the extra.
海鱼只排出少量尿液
Ocean fish only make a tiny amount of urine,
但这一点点尿也几乎
and what little pee they make is almost as
和海水一样咸
salty as the pool they pee in.
而淡水鱼要面对的问题正好相反
Freshwater fish have the opposite problem.
它们体内水分比外界要咸
Their insides are saltier than where they live,
所以水会通过皮肤和鱼鳃
so water is constantly leaking *in*
不断渗“入”它们体内
through their skin and gills.
就像我们刚刚放进纯水里的鸡蛋一样
It’s just like the naked egg we put in purewater.
鸡蛋里的浓度大于外界
The inside of the egg is saltier than the water around it,
所以水会进去
so water flows in
然后鸡蛋就会膨胀!
and the egg swells up! Plus,
除此之外 鱼还会从食物中获取更多水分
they get even more water from theirfood.
所以即使它们就在水里也不会去喝水
So even in their wet world, they never have to take a drink.
淡水鱼必须要不断的“排水”
Freshwater fishes have to *get rid* of water constantly
从而避免细胞过度吸水而破裂
to keep their cells from bursting,
这意味着它们需要尿很多尿
which means they pee *a lot*.
它们几乎一直在尿尿
They’re pretty much peeing all the time.
如果我要和淡水鱼尿一样多
If I peed as much as a freshwater fish,
我一天得尿28升水
I’d release up to 28 liters a day,
这是我平常量的20倍
which is about 20 times more pee than I usually make.
而鱼的话 在院子里尿尿也让邻居们受益匪浅
For fish, peeing in the yard is a big help to their neighbors.
鱼尿里富含氨和磷 而氨是种含氮的化合物
Fish pee is full of ammonia, a nitrogen containing compound, and phosphorous,
这两种营养物质都是植物必需的
both nutrients that plants crave.
并且它对海藻和珊瑚礁也有帮助
These also help feed algae and coral reefs,
就像液肥一样
like a liquid fertilizer
有益于整个水生生态系统
that helps keep aquatic ecosystems healthy.
而鱼就像会游泳
Fish are little swimming,
会小便 会自动回收营养的小植物
urinating, nutrient recycling plants.
有些鱼会很需要这种平衡作用
Some fish get crazy with this salt-and-water balancing act.
有些鱼能生活在特别咸的水中
Some are able to live in water so salty
但却很难生存在浅水层
it’s hard for them to stay below the surface.
还有一些 比如三文鱼
Others, like salmon,
可以调整体内化学反应在咸水和淡水中生存
can tweak their body chemistry to move between salty and fresh water.
在盐平衡方面 鲨鱼和它的同类则特别奇怪
Sharks and their relatives are especially weird when it comes to salt balance.
它们用一种特殊的酶
Using a special enzyme, they stuff urea–
将尿素(另一种含氮物)注入身体组织
another nitrogen containing compound–into their tissues.
通过内部转化的离子
By loading their insides with another ion,
可以避免水从它们身体里跑出来
they keep water from wanting to rush out of their bodies.
这也是为什么它们的肉闻着有股尿味
It’s also why their meat smells like pee.
幸好 我们人类(闻了闻腋窝)不会这样
Thankfully, we (sniff sniff armpit) don’tdo that.
味道还不错
I smell great.
但我们的水盐调节能力
But we do owe our ability to regulate
确实要归功于我们的鱼祖先
water and salt to our fishy ancestors.
科学家们认为对大多数活体动物来说
Scientists think that a healthy salt level for the bodies of most living animals
正常情况下的体内水盐浓度
is about the same concentration
与生命开始的远古海水浓度差不多
as the ancient oceans where life began.
你的身体就可以向你证明
You even have evidence of this in your body.
在我们出生之前
Before we’re born,
人类胚胎会发育出三种不同类型的肾脏
human embryos develop three different types of kidneys.
其中两个会被吸收 最后一个会变成一对肾脏
Two get absorbed, and one eventually becomes the final pair.
而另外两个则是人类进化遗留下来的:
The extra organs are an evolutionary leftovers:
比如我们在原始鱼中看到早期的肾脏
early kidneys that we also see in primitive fish,
被用来维持身体的水盐平衡
who use it to balance their salty bodies.
随地尿尿先生(I pee freely)有首诗:
It reminds me of the famous poem by I.P. Freely:
一闪一闪小鱼儿
Tinkle tinkle, little fish
还是平衡最重要
Homeostasis is what you wish
海洋就是你厕所
The ocean’s your toilet, and even thoughyou soil it
脏没关系尽情尿
Urea-ly have masteredyour niche.
好奇不灭
Stay curious.
感谢Stream Curiosity对PBS Digital Studios的支持
Big thank you to curiosity stream for supporting PBS Digital Studios
Curiosity Stream是一项流媒体订阅服务
the Curiosity Stream is a subscription streaming service
提供多名电影制作人的纪录片及非小说电影作品
that offers documentaries and nonfiction titles from a variety of filmmakers
其中还包括Curiosity Stream的原创作品
including curiosity stream originals for
比如《古文明与科学》三部曲
instance curiosity stream offers deep time history the
它甚至记录了在我们还不懂科学以前
three-part series chronicling how human history has been shaped by science
科学是如何影响人类历史的
even before we knew what science was from
从人类首次发现如何获得能量的神奇方法
the surprising ways that humans first figured out how to harvest energy to
到科学革命如何将盐和胡椒摆上你的餐桌
how the Scientific Revolution ended up putting salt and pepper on your table you
学习更多知识请访问curiositystream.com/smart
can learn more at curiositystream.com /smart and
注册时请输入smart
use the code smart during the signup process

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