Why fish are better at breathing than you are - Dan Kwartler

翻译人员: Sabrina Wang 校对人员: Aijia Yang

In 2019, Eliud Kipchoge finished a Vienna marathon

在2019年，埃鲁德·基普乔格 在维也纳的马拉松比赛中，

in one hour, 59 minutes, and 40 seconds.

以1小时59分40秒的成绩完赛。

This staggering time broke the two-hour barrier

这一惊人记录 打破了大多数长跑者

that most runners previously deemed impossible.

认为不可能突破的两小时大关。

However, some researchers weren't as surprised.

一些研究人员对此却并不感到惊讶。

Recent studies investigating if humans could maintain such a high pace

最近的研究在调查人类是否能在 马拉松全程中保持如此高的速度时

for the length of a marathon had found that elite runners

发现长跑精英的摄氧量

can take in twice as much oxygen as non-runners.

是非跑步者的两倍。

And it’s likely that this superhuman ability played a role in Eliud’s victory.

这种超人的能力很可能在埃鲁德的 获胜中发挥了作用。

But when it comes to breathing efficiently,

但在呼吸效能方面，

not even the best runners in the world can compete with the average fish.

即使是世界上最好的跑者 也无法与普通的鱼媲美。

That’s right— you’re looking at some of the best breathers on Earth;

没错---你现在看到的 是世上最优秀的呼吸者之一；

which actually makes sense when you consider how little oxygen there is

考虑到它们的水生环境中 氧气含量很少，

in their aquatic environments.

这其实是有道理的。

Fish can breathe in a variety of ways,

鱼类可以通过多种方式呼吸，

but the most common is through the use of gills.

但最常见的是通过鱼鳃。

These branching organs typically come in four pairs,

这些分支器官通常分为四对，

all enclosed in gill chambers.

都被包裹在鳃腔内。

These chambers are protected by opercle, or gill covers,

这些腔室由鳃瓣或鳃盖保护，

which are just as essential to underwater breathing as the gills themselves.

鳃盖和鱼鳃本身一样， 对水下呼吸至关重要。

When most fish take a breath,

大多数鱼在呼吸时，

they first close these covers and take a gulp of water.

它们会先合上这些鳃盖， 然后喝一大口水。

Then, they open their opercle,

之后，它们会打开鰓盖，

creating a pressure differential that pulls water through the gills,

产生压力差，促使水量流经鱼鳃。

which are composed of thread-like filaments spaced evenly along a gill arch.

鱼鳃由均匀排列在鳃弓上的 线状鳃丝组成。

These filaments are covered in countless small blood vessels called capillaries,

这些鳃丝被无数称为毛细血管的 小血管所覆盖，

in addition to tiny extensions known as gill lamellae

此外，还有被称为鳃瓣的 微小延伸部分，

which further increase the gill’s surface area.

进一步增加了鱼鳃的表面积。

When water passes over these capillaries,

当水流经这些毛细血管时，

the membrane is thin enough for the fish’s red blood cells

膜足够薄，足以让鱼的红细胞

to pull dissolved oxygen from the water into the bloodstream.

将溶解的氧从水中吸收到血液中。

And just like when we breathe with our lungs,

就像我们用肺呼吸一样，

this process releases carbon dioxide,

这个过程会释放出二氧化碳，

which passes out into the water through the open gill cover.

通过打开的鳃盖而排出到水中。

This technique only works underwater—

这种技术只能在水下起作用---

on the surface, the pressure differential created by opening and closing gill covers

在水面上， 打开和关闭鳃盖所产生的压力差

isn’t strong enough to pull in sufficient air.

不足以吸入足够的空气。

But under the surface, it’s remarkably efficient.

但在水下，这种方法却极为有效。

Inside the lamellae, blood flows in the opposite direction to the water,

在鳃片内部， 血液与水流的方向正好相反

creating a counter-current system that optimizes gas exchange.

形成了一个逆流系统， 从而优化了气体交换。

In fact, gills can absorb roughly 75% of the oxygen passing through them;

事实上，鱼可以吸收大约75% 通过鱼鳃的氧气；

that’s twice the percentage of oxygen our lungs extract from a breath of air.

这相当于人的肺从一口空气中 提取的氧气量的两倍。

Fish also breathe much more frequently than we do.

鱼类的呼吸频率也比我们高得多。

The average adult human breathes 12 to 18 times a minute,

成年人平均每分钟呼吸12到18次，

while most fish pull water over their gills

而大多数鱼类每分钟通过鳃的水流量

anywhere from 20 to 80 times a minute.

在20到80次之间不等。

Those numbers would raise even a marathoner’s eyebrows.

这些数字连马拉松运动员 都会大吃一惊。

Thanks to this fast, frequent, and efficient breathing

得益于这种快速、频繁 和高效的呼吸，

fish process far more oxygen than we do.

鱼类处理的氧气比我们多得多。

It's also why some species can live at great depths.

这也是为什么有些鱼类 可以生活在非常深的水域。

Bodies of water get most of their oxygen from the surface,

水体的大部分氧气来自水面，

where O2 dissolves into the water and begins circulating.

在这里，氧气溶解到水中 并开始循环。

But further down, there are oxygen minimum zones,

但在更深处，还有氧气最低的区域，

with concentrations as low as 0.5 milligrams of oxygen per liter.

氧气浓度低至0.5毫克每升。

To get the oxygen they need,

为了获得所需的氧气，

fish living at these depths rely on increased gill ventilation

生活在这些深海中的鱼类 依赖于增加鳃的通气量

and hearts that pump high volumes of oxygenated blood throughout the body.

和能将大量含氧的血液 输送到全身的心脏。

Even with these tricks, sometimes there's still not enough oxygen to go around,

即使有这些技巧， 有时氧气量还是会不够用，

forcing fish to adapt more extreme solutions.

这迫使鱼类采取更极端的适应策略。

For example, the Australian lungfish lives in a habitat

例如，在澳大利亚肺鱼生活的栖息地

where the water level drops precipitously in August and September,

那里的水位在八月和九月期间 会急剧下降、

making it almost impossible to survive with gills alone.

仅仅靠鳃，几乎无法生存。

Fortunately, these fish have gills and lungs.

幸运的是，这些鱼既有鳃又有肺。

Using their long, thin limbs,

利用它们细长的肢体，

they can lift their mouths above the surface and take deep breaths of air,

它们能够把嘴伸出水面， 深深地吸一口空气，

allowing them to survive out of the water for several days.

这能让他们在水外存活数天。

And other species of lungfish can survive above ground even longer

而其他种类的肺鱼， 通过在泥和粘液的茧中，

in cocoons of mud and mucus.

可让它们在地面上生存更长的时间。

Fortunately, for most fish these extreme adaptations aren’t necessary.

幸运的是，对于大多数鱼类来说， 这些极端的适应是不需要的。

After all, 71% of Earth is covered in H2O,

毕竟，地球71%的面积被水覆盖，

giving these aquatic animals plenty of room to flaunt their gills’ skills.

让水生动物们有足够的空间 来炫耀它们用鳃呼吸的技能。