Have you ever heard the phrase “to drink like a fish?”

你聽過「像魚一樣酗酒」這個片語嗎？

Well, unless you're a ocean dwelling species, that probably means staying sober.

除非你是生活在海洋的生物，否則那可能表示沒喝醉。

Because freshwater fish don't drink!

因為淡水魚不會喝酒！

Saltwater fish on the other hand?

那麼鹹水魚呢？

They're constantly drinking.

牠們一直在喝水。

But if some fish drink all the time and other fish don't drink at all, we're left with

但如果有些魚一直在喝水而其他魚完全不喝水，

an obvious question: Do fish pee?

就產生了一個明顯的問題：魚會尿尿嗎？

What… you've never wondered that?!

什麼...你從來不好奇？！

Water is essential to life as we know it.

如我們所知，水是生命所必需。

To keep their chemistry running smoothly, living things need just the right amount of

為了保持生物化學作用順暢進行，活體生物體內

water in their bodies.

需要恰好的水量。

You'd think that fish have it made when it comes to staying hydrated, but it's not so easy.

你可能會想魚可以輕而易舉補充水分，但並非這麼簡單。

Fish gills lets oxygen flow into their bodies, but they're also letting water constantly escape.

魚的鰓讓氧氣流入體內，但也讓水持續流失。

Ocean water is *saltier* than the inside of fish.

海水比魚的體內更鹹。

So water wants to move from the inside out to balance that out.

所以水分想要從體內移動出去以達成平衡。

That's a problem if you're a fish who wants to stay alive.

如果你是一隻想要活命的魚，那會是個問題。

It's a process called osmosis, and we can demonstrate that with these eggs.

這是一個叫做滲透作用的過程，我們可以用這些蛋來演示。

I've dissolved the shells away, leaving a membrane that'll allow water to pass through.

我已經把殼去除了，留下一層可以讓水通過的膜。

One is covered in pure H2O.

一顆放入純水中。

And one goes into sugar syrup.

而另一顆放入糖漿中。

The syrup contains lots of sugar molecules, and not much water, so water passes out of

糖漿含有很多糖分子，沒有那麼多水，所以水從蛋流出以達平衡，

the egg to balance it out, and the egg shrinks!

而蛋就皺縮了！

Life is all about balance.

平衡是生命大事。

Now, we keep the salts and dissolved chemicals in our blood balanced by flushing the extra

現在，我們藉由腎臟沖出多餘物，口渴時飲入淡水，

through our kidneys, and by drinking fresh water when we're thirsty.

以保持血中鹽分與溶解的化學物質平衡。

But ocean fish only have one option: drink salt water in order to get the H2O they need to stay alive.

但海水魚只有一個選擇：喝鹹水以得到生存必需的水。

And most of them do that a *lot*.

而他們多數都很常這麼做。

But they need to get rid of the salt without dehydrating, which they do using special cells

但牠們必須在不脫水的前提下去除鹽分，牠們藉由鰓中

in the gills that pump out the extra.

特殊的細胞排出多餘的鹽分。

Ocean fish only make a tiny amount of urine, and what little pee they make is almost as

海水魚的尿很少，而牠們的尿幾乎和

salty as the pool they pee in.

所尿入的池水一樣鹹。

Freshwater fish have the opposite problem.

淡水魚的問題則相反。

Their insides are saltier than where they live, so water is constantly leaking *in*

牠們體內比所居住的環境更鹹，所以水持續

through their skin and gills.

經由皮膚和鰓流「入」。

It's just like the naked egg we put in pure water.

就像我們放入純水的剝殼蛋。

The inside of the egg is saltier than the water around it, so water flows in

蛋的內部比周圍的水還要鹹，所以水分流入

and the egg swells up!

蛋就腫起來了！

Plus, they get even more water from their food.

加上牠們從食物得到更多的水分。

So even in their wet world, they never have to take a drink.

所以即使在牠們潮濕的世界裡，牠們從不需要飲水。

Freshwater fishes have to *get rid* of water constantly to keep their cells from bursting,

淡水魚必須持續「排出」水分以免細胞爆掉，

which means they pee *a lot*.

也就是說牠們尿「很多」。

They're pretty much peeing all the time.

牠們幾乎無時無刻不在尿尿。

If I peed as much as a freshwater fish, I'd release up to 28 liters a day, which is about

如果我的尿量和一隻淡水魚一樣多，我一天會排出高達 28 公升的尿，大約是

20 times more pee than I usually make.

我一般尿量的 20 倍。

For fish, peeing in the yard is a big help to their neighbors.

對魚來說，在後院小便對鄰居而言是一大助益。

Fish pee is full of ammonia, a nitrogen containing compound, and phosphorous, both nutrients

魚的尿富含氨，一種含氮物質，還有磷，

that plants crave.

兩者都是植物所必需的養分。

These also help feed algae and coral reefs, like a liquid fertilizer that helps keep aquatic

這些物質也為海藻和珊瑚礁提供養分，就像是幫助維持水生

ecosystems healthy.

生態系統健康的液體肥料。

Fish are little swimming, urinating, nutrient recycling plants.

魚是游泳、排尿、養分循環的小工廠。

Some fish get crazy with this salt-and-water balancing act.

有些魚對這種鹽水平衡行為陷入瘋狂。

Some are able to live in water so salty it's hard for them to even stay below the surface.

有些魚可以生活在鹹到甚至牠們都很難待著的水中。

Others, like salmon, can tweak their body chemistry to move between salty and fresh water.

其他如鮭魚可以改變身體的化學組成，可在鹹水和淡水之間移動。

Sharks and their relatives are especially weird when it comes to salt balance.

鯊魚和牠們的親戚在鹽類平衡尤其怪異。

Using a special enzyme, they stuff urea–another nitrogen containing compound–into their tissues.

利用一種特別的酵素，牠們將尿素 - 另一種含氮物質 - 塞入牠們的組織。

By loading their insides with another ion, they keep water from wanting to rush out of their bodies.

體內藉由另一種離子承載，防止水分從體內跑出去。

It's also why their meat smells like pee.

這也是為什麼鯊魚肉聞起來像尿。

Thankfully, we (sniff sniff armpit) don't do that.

謝天謝地，我們 (聞腋下) 不這麼做。

I smell great.

我聞起來好極了。

But we do owe our ability to regulate water and salt to our fishy ancestors.

但我們調節水和鹽的能力確實歸功於我們的魚祖先。

Scientists think that a healthy salt level for the bodies of most living animals is about

科學家認為對多數活的生物體健康的鹽度大約

the same concentration as the ancient oceans where life began.

與生命起源的古老大海濃度一致。

You even have evidence of this in your body.

你的體內甚至有證據。

Before we're born, human embryos develop three different types of kidneys.

在我們出生前，人類胚胎發育出三種不同的腎臟。

Two get absorbed, and one eventually becomes the final pair.

兩種被吸收了，而一種變成最後一對。

The extra organs are an evolutionary leftovers: early kidneys that we also see in primitive

多出來的器官是演化的殘留物：原始魚類體內也可見的早期腎臟，

fish, who use it to balance their salty bodies.

用來平衡牠們體內的鹽分。

It reminds me of the famous poem by I.P. Freely:

這使我想起了 I.P. Freely 有名的詩：

Tinkle tinkle, little fish Homeostasis is what you wish

叮噹叮噹，小魚兒。平衡是你所願。

The ocean's your toilet, and even though you soil it

大海是你的便所，即使你將它弄髒，

Urea-ly have mastered your niche.

尿素也會予你助益。

Stay curious.

保持好奇。