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We usually think of scallops as tasty, pan-seared delicacies, or the classic shape of clipart seashells.
我们常认为扇贝是一种美味的煎炸美食，或是典型剪纸艺术般的海洋贝类。
But last week, biologists revealed that they’re worthy of way more than a special spot on a menu:
但上周，生物学家透露，它们的价值并不仅限于菜单之上：
Their visual system is amazingly complex, and includes up to 200 telescope-like eyes.
它们的视觉系统惊奇地复杂，其中包含高达200个望远镜式的眼睛。
Most eyes, from the fancy compound eyes of bees to our own simple ones, focus light with a lens onto a retina,
从蜜蜂别致的复眼到我们人类的眼睛，大部分眼睛利用透镜将光聚集到视网膜上，
which contains light-sensitive photoreceptors.
视网膜含有光敏光感受器。
Scallop eyes, on the other hand, use mirrors to do this focusing,
另一方面，扇贝的眼睛是利用镜子进行聚焦，
which is why people sometimes compare them to telescopes, like Hubble, despite their tiny size.
这就是为什么人类有时将它们比作望远镜的原因，比如哈勃，虽然它们是迷你版的。
This much had been known for half a century, thanks to a British vision researcher.
多亏了英国视觉研究员，这个知识已存在半个世纪了。
But what the mirrors are made out of, and exactly how sight worked for the scallops, remained a mystery.
但这些镜子是由什么组成的以及它是如何起到作用的仍是个谜。
That’s mostly because their eyes are only about a millimeter big.
这主要由于它们的眼睛只有毫米那么大。
And every time scientists tried to prepare the delicate eye tissue for a microscope, samples dried out and fell apart.
每当科学家们试图准备对眼组织进行显微镜观察时，样本就已经枯竭并脱落。
Enter cryogenic scanning electron microscopy, or cryo-SEM.
低温扫描电子显微镜，或冷冻扫描。
The technique uses liquid nitrogen to quickly chill samples, allowing researchers to keep tissue intact and hydrated.
这项科技利用液氮快速冷冻样本，这样研究员就能保持组织的完整性和水分。
Reporting in the journal Science, a team used this method and discovered that scallop eye mirrors are made out of guanine.
《科学》杂志报道，一个团队采用了这种方法后发现扇贝的眼睛镜子是由鸟嘌呤组成。
You might have heard of guanine because it’s one of the four bases that makes up DNA.
你可能听过鸟嘌呤，因为这是组成DNA的四个基质之一。
But crystals made of guanine have weird optical properties that many organisms use to survive.
但由鸟嘌呤组成的晶体有着怪异的光学性质，是许多生物体赖以生存的物质。
Like, it’s what makes fish scales look iridescent or shiny.
比如，它能让鱼鳞看起来闪闪发光。
In scallops, the guanine crystals are in the shape of square tiles.
在扇贝中，鸟嘌呤晶体是方砖状的。
These tiles are stacked 20 to 30 sheets thick, each layer separated by a bit of cytoplasm.
方砖堆积20-30层厚，每层都被一点细胞质隔开。
And they’re arranged to form a curved mirror at the back of each eye.
它们会在每只眼睛的后边形成一面曲面镜。
This is similar to how segmented mirror telescopes— the largest and most powerful telescopes in the world—focus light.
这和分节望远镜——世界上最大最强的望远镜发光原理相似。
So, scallop eyes are more like the James Webb Space Telescope than Hubble.
所以，相比哈勃，扇贝眼睛更像是詹姆斯·韦伯空间望远镜。
The researchers think the precise layering of the crystals causes them to mostly reflect blue and green wavelengths of light—
研究员认为晶体的精密分层致使它们主要反射蓝色和绿色的光波长——
which is what you’d expect a scallop to need to live under the sea.
这是让扇贝在海里寿命更长的物质。
And maybe even more impressive is the fact that scallop eyes have two retinas.
或许更让人惊叹的是扇贝的眼睛有两个视网膜。
Instead of being at the back of the eye, like ours, the retinas are two strips of tissue in the middle of the eye,
不像人类的眼睛-视网膜在眼睛后边，扇贝的视网膜是位于眼睛中间的两个组织带，
onto which light gets focused after it’s reflected off the back mirror.
在反射到后镜后，光就聚集如此。
The team took a 3D scan of the eye, and simulated some views with a computer.
该团队对眼睛进行3D扫描，并用电脑刺激视野。
From these models, they saw that the guanine mirror is uniquely shaped and oriented to focus different light on each retina.
从这些模型中，他们发现鸟嘌呤镜形状独特且将不同的光聚集在每个视网膜上。
So they think scallops see two images at once.
所以他们认为扇贝一次能看到两个画面。
The smaller, outer retina appears to be specialized for quick changes in light that are directly in front of the eye,
外层更小的那层视网膜专用于直射眼前快速变化的光，
like the sudden shadowy presence of a predator.
比如，食肉动物突然出现。
And the larger inner retina is better at picking up light in the periphery.
位于内部的更大点的视网膜擅于捕捉周围的光。
It’s also more sensitive to light overall, and gives the clearest picture.
它对于周围的光更加敏感，并能形成非常清晰的画面。
So biologists think this retina is important for the scallop to keep tabs on its surroundings, even in low-light.
因此，生物学家认为对于扇贝来说，这层视网膜对观察周围情况，有着很重要的作用，即使是在微光之中。
Which is probably pretty helpful if you live under a rock in the ocean.
如果你生活在海洋中与世隔绝的地方，这一点相当有用。
And now: More sea creature news!
现在：更多海洋生物消息！
Because last week, a team of biologists also announced that they think the first animals to break off from all others
因为上周，一个生物学家团队同样宣布，他们认为第一种和其他种类脱离开来
and form a separate branch on the tree of life were sponges, not comb jellies.
并在生命之树上形成单独分支的动物是海绵而非栉水母。
It’s a debate you probably didn’t know was happening.
这可能是一场悄无声息的争论。
But it has huge ramifications in thinking about animal evolution.
但这对动物进化的思索有着巨大影响。
And for years, scientists have been split on the matter.
多年来，科学家们对这个问题都持不同意见。
Sponges, also known as poriferans, are very simple animals.
海绵，也被称为多孔动物，是非常简单的动物。
So simple that many people confuse them with plants. They don’t move or have any organs to speak of.
因为过于简单，许多人都将其与植物相混淆。它们一动不动，更别说有任何器官了。
Instead, their bodies are full of pores that let water pass through.
相反，它们的身体却满是能够让水穿过的气孔。
And specialized cells called choanocytes capture food particles in the water.
被称为环细胞的分化细胞在水中捕获食物颗粒。
Comb jellies, or ctenophores, are also pretty simple,
栉水母或栉水母门动物也很简单，
although not as much as sponges because they actually have a basic nervous system.
虽然不如海绵一样，因为事实上，它们有着基本的神经系统。
And they look kind of like jellyfish, but they don’t have any stinging cells.
它们看起来像是水母，但它们没有任何刺丝囊。
The confusion has been over which of these animals is the sister to all others, or what scientists call the sister group.
困惑已被解决了，这些动物是所有其他动物的姐妹版，或者是科学家所说的姐妹团。
In other words, if you look at the evolutionary tree, which group is split off by itself from other animals.
换句话说，如果你看看进化谱，姐妹团被自己和其他动物分离开来。
This doesn’t necessarily mean one animal is older than another, or that we humans evolved from one or the other.
这并不是意味着一种动物比其他的动物更老，或者我们人类也是从中之一进化而来。
What it does tell us, though, is what the common ancestor of all animals might have been like.
这确实能够告诉我们，所有动物的共同祖先可能是什么样的。
The problem is that researchers have gotten different answers when they look at the genomes of these animals,
问题是当观察这些动物的基因组、将其与其他动物相比较并利用进化电脑模型制作系谱树时，
compare them to others, and use computer models of evolution to make a phylogenetic tree.
研究员们却得到了不同的答案。
If you include specific amino acid changes, you usually get sponges.
如果你加入特定的氨基酸变化，你通常会得到海绵。
But if you exclude those, or include distant organisms, like fungi, you usually get jellies.
但如果你排除了那些，或加入远隔生物体，比如真菌，你常会得到水母。
In the latest study, researchers used more statistics to filter out noise in all the data,
最近研究中，研究员利用更多统计过滤掉所有数据中的干扰，
and concluded that sponges were the real deal.
并总结到海绵货真价实。
Some scientists may still nit-pick at this result, but others seem convinced that the debate is almost over.
一些科学家仍对结果吹毛求疵，但其他科学家确信争论基本结束了。
And it kind of makes intuitive sense that the simpler animal is at the root of the family tree.
这所导致的直接感受是，越简单的动物就位于系谱图的根部。
The opposite finding would have meant that sponges would have had to lose their more complicated organ systems from a shared common ancestor.
相反的发现意味着海绵需要从共同祖先中失去更加复杂的器官系统。
So, there you have it.
因此，情况就是这样了。
An updated family tree for all of us… at least until we get more data to complete the puzzle.
我们的新版系谱图，至少要等到我们获取更多数据来完成这个谜题才行。
Alright, time for an announcement!
下面宣布一件事！
You may have heard of this by now, but we here at SciShow are trying a new thing.
你应该也听说了，但是我们科学秀要尝试新东西啦。
Sometimes—all the time—it's hard to figure out what presents to get for people.
给别人挑选礼物太困难了。
But we come across weird, cool science-y things all the time that we love and we think you or someone you know might love.
但我们有些古怪的、超酷的科学道具，我们觉得你或别人会喜欢这些东西。
So we've created a store called SciShow Finds.
所以我们建了一个叫做SciShow Finds的商店。
It's got a limited list of items that we have in very limited quantity.
商店物品数量有限。
Stuff that lets you learn, or experiment on yourself, or just show how enthused you are about the wonders of the universe.
这些东西能让你学习科学，进行科学实验，向你展现宇宙奇妙。
Someone you know is guaranteed to love these socks or this lapel pin!
你的朋友保证会喜欢这些袜子或胸针！
And we'll add new items as we find them to replace these ones as they sell out. A lot of them already sold out.
我们会随时添加新的物品。其中一些已经售完了。
And, when you buy from SciShow Finds, you're also helping support SciShow, which I appreciate a lot. So, thanks for doing that!
支持科学秀，登录SciShow Finds进行购买，感谢之至。
