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When you look at a goldfish in a bowl, it's hard to imagine there's much going on behind those googly eyes.
当你看着缸里的金鱼时，很难想象那些圆圆的眼睛里发生了很多的事情。
But biologists have found lots of amazing things about fish, like how their swim bladders let them control buoyancy.
但生物学家发现了很多关于鱼类的趣事，比如鱼类的鱼鳔如何帮助它们控制浮力。
Some fish even take their adaptations to the extreme—almost like they have superpowers.
一些鱼类甚至将它们的适应性发挥到极致—它们就像是拥有超能力一样。
Take the archerfish, which gets its name from the stealthy way it hunts.
以射水鱼为例，它们因捕猎时鬼鬼祟祟的方式而得名。
It knocks down insects by spitting out a powerful jet of water, and then its gobbles its prey up.
它们通过吐出强力水柱击倒昆虫，然后吞食猎物。
First, archerfish collect water in their mouths by making tubes with their tongues. And then they force it out by squeezing their gill covers closed.
首先射水鱼将舌头卷成导管，把水聚集在嘴里。然后它们通过挤压紧闭的鳃盖喷出水柱。
Their aim is so precise that they've been seen shooting down insects flying at 25 centimeters per second, and 2 meters above the water's surface!
它们目标非常精确，所以它们能射下以每秒25厘米速度在距离水面2以上飞行的昆虫！
Unlike Superman, archerfish aren't born with their sharpshooting skills.
射水鱼不像超人，他们并非天生就拥有这种准确射箭的技能。
Instead, young archerfish hunt in small schools and pick it up through observational learning.
相反，小射水鱼会在小学校里捕猎，并通过观察学习将猎物捡起来。
A lot of subtle calculations and practice go into each blast.
每次的射击都需要大量的精确计算和练习。
For one, light rays bend or refract when they change material, like from air to water.
当它们改变物质时，比如从空气到水，光线会弯曲或折射。
Different materials are different densities, which changes how light passes through them.
不同物质的密度都不同，这就改变了光线穿过它们的方式。
So when light reaches an archerfish's eyes, it doesn't see exactly where its prey is.
所以当光线到达一只射水鱼的眼里时，它就无法准确看到猎物的位置。
Kind of like how a pencil looks shifted when you stick it halfway into a glass of water.
有点像是当你将铅笔半身插入一杯水中，铅笔看起来就像折了一样。
To solve this, archerfish have to aim their shot carefully to compensate for the light refracting.
为了解决这个问题，射水鱼必须仔细瞄准射击，以弥补光线的折射。
Exactly how they do this math is still a bit of a mystery though. Archerfish can adjust how powerful their shot is, too.
而它们是如何计算这倒数学题的，这还是个谜。射水鱼还能够调节它们射击的力度。
For example, for a higher target, they open their mouths longer to let in more water, and release it a little more slowly.
例如，遇上较高的目标时，它们会将嘴张的更长来吸入更多的水，然后更加慢速的释放水。
This makes a more forceful jet of water that lasts longer.
这样能制造出更加强力的水柱，且持续时间更长。
Scientists have even found that archerfish seem to have some visual memory!
科学家甚至发现射水鱼有视觉记忆！
In one experiment, researchers showed archerfish two faces on a screen mounted above their tank — one they wanted the fish to target and one they didn't.
在一次实验中，研究人员利用安装在鱼缸上的屏幕向射水鱼展示了两个面孔—一种是鱼的目标，而另一个则不是。
The fish got a food reward every time they shot water at the target face.
鱼儿们每次喷水射击目标面孔时，就会获得食物奖励。
They, then showed the fish the non-target face and some new faces, to test whether they'd keep ignoring the non-target.
然后它们向鱼展示非目标面孔以及一些新面孔，以测试它们是否会继续忽略非目标。
Turns out they could! Even if the faces were in black and white and the picture was cropped.
事实证明它们会！即使这些面孔是黑白的，即使这些图画剪裁不正。
Now, this next fish has the ability to hunt using a killer tail-flip. But not in the water—on land.
下一种鱼有利用致命性尾巴弹跳捕食的能力。但不是在水中，而是在陆地上。
The mangrove killifish spends most of its time lurking in warm, muddy waters low in oxygen and fairly high in hydrogen sulfide
红树林鳉鱼的大部分时间都在温暖、浑浊的水中潜伏，这里氧含量低，硫化氢含量却很高
— the toxic compound that smells like rotten eggs.
—这是一种闻起来像臭鸡蛋一样的有毒化合物。
Those aren't exactly pleasant conditions, but the killifish tolerates them.
那并非是舒适的环境，但鳉鱼却能够忍受。
But when the water quality gets too poor, especially if there's too much hydrogen sulfide,
但当水质变得过于糟糕，特别是里边含有过多硫化氢，
the killifish hightails it out of there and spends up to two months living on land.
鳉鱼会马上逃离此地并在陆地上生活两个月。
If most fish leave water, the thin plates of tissue that make up the gills, called gill lamellae, collapse.
大部分鱼如果都离开水，那么构成鳃的组织薄板—鳃瓣，会衰竭。
So they can't exchange oxygen and carbon dioxide with the environment. Basically, they can't breathe.
因此它们无法在环境中交换氧气和二氧化碳。它们基本都不会呼吸。
The killifish avoids this by growing more cells that act like scaffolding in between their lamellae, known as interlamellar cell masses.
为了避免这个问题，鳉鱼会长出更多的细胞，充当鳃瓣间的脚手架，其被称为瓣间细胞群。
This scaffolding reduces the gills' surface area and exposure to air, so it protects them from drying out.
这种脚手架能够减少鱼鳃的表面面积，避免接触阳光，保护它们不被晒干。
And when they hop back in the water, the cell masses waste away and the gills work regularly again.
当它们再跳入水中时，细胞群逐渐减少，鱼鳃恢复正常工作。
Without functioning gills on land, the killifish relies on its skin for breathing.
在陆地上没有鱼鳃的运作，鳉鱼依赖自己的皮肤呼吸。
Their skin is full of special chemoreceptive neuroepithelial cells that detect when the fish is in air and trigger those changes in the gills
它们的皮肤中满是特别的化学感应神经上皮细胞用于探测，当鱼在大气环境中时，它会触发鱼鳃中的那些变化
and increase blood flow to help shuttle chemicals around.
并增加血流帮助物质的穿梭。
The relatively thin epidermis, or outer layer, is also filled with ion-exchanging cells called ionocytes.
相对较薄的表皮或外层中也满是离子交换细胞—离子细胞。
In exclusively water-dwelling fish, they're only found in the gills.
在这种独特水生鱼类中，仅在鱼鳃中被发现。
Ionocytes help maintain the levels of ions in blood so that a fish's cells can function properly.
离子细胞帮助维持血液中离子含量，这样，鱼的细胞才能正常运作。
The killifish's final trick is a super-powerful tail flip that it uses to hunt on land.
鳉鱼的最后一招是超级强悍的尾巴弹跳，用于陆地捕食。
It contracts the muscles on the upper side of its body, making it curl into a "C" shape.
它会收缩身体上边的肌肉，卷成“C”形。
Then, a wave of contractions forces its tail onto the ground and flips it high into the air, so it can grab insects high above it.
然后一股收缩力迫使鱼的尾巴贴在地面并弹至空中，这样它就能抓住高空中的昆虫。
Now, the tuskfish might be the first example of a fish that uses tools — something we'd usually associate with the great apes or humans.
猪齿鱼或许是鱼类会使用工具的第一个例子—我们常将其与类人猿或人类相联系。
Several species of tuskfish like to eat juicy clams. But the edible part is hidden inside a hard shell.
猪齿鱼中的一些种类喜欢吃蛤蚌。但其可食用部分隐藏在坚硬的壳中。
The tuskfish gets its name from its prominent teeth.
猪齿鱼因其翘露的牙齿而得名。
It uses these to grip a clam, swim over to a nearby rock, and smash the shell it by throwing the clam or flicking its head.
它们利用牙齿抓住蛤蚌，并游到附近的岩石，通过扔砸蛤蚌和弹动头部来砸开外壳。
In a way, it's using a rock like an anvil.
它们将岩石用作铁砧。
While there's no one definition of tool use in animals, scientists generally agree that it has something to do with holding
对于动物使用工具还没有一个定义，科学家通常认为是需要握住某件物品
or manipulating an object to alter the environment or attain a goal.
或操控一件物品用于改变环境或实现一个目标。
And researchers have noticed that tuskfish will pick a rock that's big and solid enough to break a clam shell, and they'll use a favorite rock again and again.
研究人员注意到猪齿鱼会选择大且坚硬的石头用于砸开蛤蚌壳，而且它们会重复使用一块喜欢的岩石。
Some scientists argue that because the fish are grabbing the clam instead of the rock, they're not really using tools.
一些科学家则认为这些鱼是要抓蛤蚌而非岩石，它们并不是真的使用工具。
But fish don't have any grasping limbs to hold onto tools. So if a fish held a stone in its mouth, the food would probably float away.
但是鱼类并没有任何四肢能够抓住工具。所以如果鱼将石头放在嘴里，食物就会飘走。
So maybe the way we think about tool use needs to consider an animal's environment and anatomy a bit more.
所以或许我们在考虑工具使用时，需要更多的考虑到这种动物的环境和骨骼。
But either way, the tuskfish is still showing off some skills that are more complex than you might expect.
但不管怎样，猪齿鱼仍展示了一些比人类想象中还复杂的技能。
Thanks for watching SciShow, which is produced by Complexly, a group of people who want to help humans think about the world we live in more deeply.
感谢收看本期科学秀，本期科学秀由Complexly出品。Complexly帮助大家更加深层思考这个世界。
If you want to learn more about wildlife, you can check out Animal Wonders, another one of our channels, at youtube.com/animalwondersmontana.
如果你想了解更多野生动植物知识，请登录youtube.com/animalwondersmontana，观看我们的另一个频道Animal Wonders。
