视频介绍
蜻蜓可以以近乎完美的精度捕捉猎物，傲立所有捕食者。但是，只有很少神经元的蜻蜓是如何获得如此出色的表现的呢？大胆的神经科学家用传感器和人造苍蝇，探究了蜻蜓如何准确无误地锁定猎物，并在几毫秒内将其捕捉。
片长：5：04
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If I asked you to think of a ferocious killer animal, you'd probably think of a lion, and for all the wonderful predatory skills that a lion has,格雷格·盖奇：如果让你想象凶猛的捕食动物，你可能会想到狮子。但即便狮子捕食技巧出色，
it still only has about a 20 percent success rate at catching a meal.它捕食的成功率也仅有两成。
Now, one of the most successful hunters in the entire animal kingdom is surprising: the dragonfly.要说动物王国中最成功的捕食者，答案可能让你大吃一惊，它就是蜻蜓。
Now, dragonflies are killer flies, and when they see a smaller fly, they have about a 97 percent chance of catching it for a meal.蜻蜓是飞行猎手，当他们看到比自身体型小的飞虫，他们有 97% 的概率捕捉它，
And this is in mid-flight.这整个过程仅在飞行时就完成！
But how can such a small insect be so precise?一个如此小的昆虫 为何有如此高的精准度？
In this episode, we're going to see how the dragonfly's brain is highly specialized to be a deadly killer.在这一集中，我们将会看到蜻蜓的大脑如何造就致命杀手。
So what makes the dragonfly one of the most successful predators in the animal kingdom?蜻蜓是如何成为动物中最成功的捕食者之一呢？
One, it's the eyes.第一，眼睛构造。
It has near 360-degree vision.蜻蜓拥有将近 360° 的视角。
Two, the wings.第二，翅膀结构。
With individual control of its wings, the dragonfly can move precisely in any direction.通过对每个翅膀的独立控制，蜻蜓可以在任意方向上精确移动。
But the real secret to the dragonfly's success is how its brain coordinates this complex information between the eyes and the wings and turns hunting into a simple reflex.但蜻蜓成功的真正秘诀，是其大脑会整合来自眼睛和翅膀的复杂信息，并将捕猎行为转变为躯体的简单反射。
To study this, Jaimie's been spending a lot of time socializing with dragonflies.为了研究清楚其中的原理，杰米花了很多时间和蜻蜓相处。
What do you need to do your experiments?实验中你都需要些什么？
First of all, you need dragonflies.首先，蜻蜓必不可缺。
I have a mesh cage to catch the dragonflies.我用捕虫网抓它们。
The more I worked with them, the more terrified I got of them.越研究它们，就越害怕它们。
They're actually very scary, especially under a microscope.它们实际上非常吓人，特别是在显微镜下。
They have really sharp mandibles, are generally pretty aggressive, which I guess also helps them to be really good predators.他们的下颌骨非常锋利，很有攻击性，这也帮助他们成为捕食好手。
In order to learn what's going on inside the dragonfly's brain when it sees a prey,为了研究蜻蜓看到猎物时的大脑活动，
we're going to eavesdrop in on a conversation between the eyes and the wings, 我们决定偷听蜻蜓眼睛和翅膀间的一次对话。
and to do that, we need to anesthetize the dragonfly on ice and make sure we protect its wings so that we can release it afterwards.为此，我们需要用冰水麻醉蜻蜓，并确保翅膀完好无损，以便后续进行放生。
Now, the dragonfly's brain is made up of specialized cells called neurons and these neurons are what allow the dragonfly to see and move so quickly.蜻蜓大脑中有很多特殊的细胞，那就是神经元。这些神经元使得蜻蜓能够快速发现和移动。
The individual neurons form circuits by connecting to each other via long tiny threads called axons 独立的神经元通过细长的轴突连接彼此，
and the neurons communicate over these axons using electricity.神经元在轴突上用电信号进行交流。
In the dragonfly, we're going to place little metal wires, or electrodes, along the axon tracks, and this is what's really cool.在蜻蜓体中，我们将沿着轴突放置一些小的金属线和电极，这整个过程都很酷。
In the dragonfly, there's only 16 neurons; that's eight per eye that tell the wings exactly where the target is.蜻蜓只有 16 个神经元：每只眼睛各有 8 个，用来告诉翅膀目标的具体方位。
We've placed the electrodes so that we can record from these neurons that connect the eyes to the wings.放置电极后，我们就可以记录眼睛和翅膀之间的神经元电信号。
Whenever a message is being passed from the eye to the wing, our electrode intercepts that conversation in the form of an electrical current,每当有“消息”从眼睛发往翅膀，我们的电极都会将这次“对话“ 以电流的形式记录下来，
and it amplifies it.并对电流进行放大。
Now, we can both hear it and see it in the form of a spike, which we also call an action potential.现在我们能看到并听到电流脉冲，我们称之为动作电位。
Now let's listen in.一起来听听。
Right now, we have the dragonfly flipped upside down, so he's looking down towards the ground.现在我们把蜻蜓倒置，它现在眼朝地面。
We're going to take a prey, or what we sometimes call a target.我们现在放置一个猎物，或者说目标，
In this case, the target's going to be a fake fly.这里我们使用一个假苍蝇作为目标。
We're going to move it into the dragonfly's sights.我们将在蜻蜓的视野里移动它。
Oh!哇哦！
Oh, look at that.噢，瞧呀。
Look at that, but it's only in one direction.快看，但只在朝固定方向。
Oh, yes!太棒了！
You don't see any spikes when I go forward, but they're all when I come back.当我向前移动的时候没有出现任何脉冲，但回来的时候脉冲出现了。
In our experiments, we were able to see that the neurons of the dragonfly fired when we moved the target in one direction but not the other.实验发现，当目标仅朝一个方向移动时，蜻蜓的神经元被激活了，在另一个方向却没有。
Now, why is that?这是为什么呢？
Remember when I said that the dragonfly had near 360-degree vision.之前我说到，蜻蜓拥有 360° 的可视范围，
Well, there's a section of the eye called the fovea and this is the part that has the sharpest visual acuity,蜻蜓眼睛上有一个称为“中央凹”的区域，这是蜻蜓视力最敏锐的部分。
and you can think of it as its crosshairs.你可以把它看作十字准线。
Remember when I told you the dragonfly had individual precise control of its wings?还记得吗？蜻蜓能独立控制每个翅膀，
When a dragonfly sees its prey,当它发现猎物时，
it trains its crosshairs on it and along its axons it sends messages only to the neurons that control the parts of the wings that are needed to keep that dragonfly on target.会试图将准星对准猎物，它会沿着轴突发送信息给控制翅膀的神经元，由这些神经元控制蜻蜓来对准目标。
So if the prey is on the left of the dragonfly, only the neurons that are tugging the wings to the left are fired.所以，如果猎物在蜻蜓的左侧，那么只有控制左侧翅膀的神经元会被激活。
And if the prey moves to the right of the dragonfly, those same neurons are not needed, so they're going to remain quiet.如果猎物移动到蜻蜓的右侧，这些神经元就不再需要了，所以它们会保持安静。
And the dragonfly speeds toward the prey at a fixed angle that's communicated by this crosshairs to the wings, and then boom, dinner.神经元确定好翅膀的角度后，蜻蜓就会朝猎物径直飞去。当当，晚饭到手了。
Now, all this happens in a split second, and it's effortless for the dragonfly.所有这些都在一瞬间发生，这对蜻蜓来说毫不费力，
It's almost like a reflex.就像是本能反应。
And this whole incredibly efficient process is called fixation.这个惊人高效的捕猎过程被称为固定。
But there's one more story to this process.但还有一件事需要考虑。
We saw how the neurons respond to movements, but how does the dragonfly know that something really is prey?我们看到神经元如何响应运动，但是蜻蜓如何判断谁是猎物呢？
This is where size matters.这就需要考虑猎物的体型了。
Let's show the dragonfly a series of dots.我们来给蜻蜓展示一系列圆点。
Oh, yeah!没错！
Yeah, it prefers that one.它对那个圆点比较有反应。
Out of all the sizes, we found that the dragonfly responded to smaller targets over larger ones.在所有的体型中，我们发现蜻蜓更倾向于选择体型小的目标。
In other words, the dragonfly was programmed to go after smaller flies versus something much larger, like a bird.换句话说，蜻蜓被设定为捕捉体型比自己小的飞虫，而不是更大的目标，比如鸟类。
And as soon as it recognizes something as prey, that poor little fly only has seconds to live.一旦它识别出什么是猎物，这只可怜的小飞虫就只有几秒钟的生命了。
Today we got to see how the dragonfly's brain works to make it a very efficient killer.今天我们看到了蜻蜓的大脑如何工作，使得蜻蜓成为一个高效的猎手。
And let's be thankful that we didn't live 300 million years ago when dragonflies were the size of cats.我们得庆幸自己不是生活在 3 亿年前，那时的蜻蜓差不多跟猫一样大。
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