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生物都不断进化成螃蟹?

Why Do Things Keep Evolving Into Crabs?

Around 10 million years ago, off the coast of what’s now New Zealand,
大约一千万年前 在如今的新西兰沿海
a spiny, leggy creature with claws cruised the Pacific Ocean looking for food.
一个多刺 腿长且有爪的生物在太平洋缓慢地寻找食物
This creature was an ancient ancestor of modern-day king crabs,
这种生物是现代帝王蟹的古老祖先
known to scientists as Paralomis debodeorum.
被科学家称为Paralomis debodeorum
It had a round, spiky carapace and a body about the size of a baseball,
它有一个圆的 尖刺般的甲壳和与网球差不多大的躯干
but not much else is known about it.
但是除此之外 我们对它知之甚少
This fossil is the only one of its kind ever found.
这是迄今为止发现的唯一一块该生物化石
And, based on how modern king crabs live, scientists think that Paralomis probably lived
根据现代帝王蟹的生活习性 科学家认为
in very deep, cold water.
Paralomis可能生活在非常寒冷的深水中
But, no matter how Paralomis spent its days,
但是无论paralomis如何生存
scientists agree that if you saw one today,
科学家们一致认为 如果你现在见到一只
you’d recognize it as a crab.
你会把它认成螃蟹
But it wasn’t a crab—at least, not a “true crab.”
但是它不是螃蟹 至少不是真螃蟹
Paralomis and its modern counterparts belong to
Paralomis和它对应的现代生物同属于
an infraorder known as Anomura,
一个被称为异尾下目的下目
a huge group of crustaceans that includes everything from the porcelain crab to the coconut crab.
这是一个庞大的甲壳动物群 包括从瓷蟹到椰子蟹的所有生物
Am I the only who is really horrified by coconut….coconut crabs?
我是唯一一个真的被椰子蟹吓到的人吗?
Give me a minute.
给我一点时间
Anyway, none of those animals that we call crabs are actually crabs.
无论如何 我们称之为螃蟹的那些动物实际上都不是螃蟹
They all evolved from crustaceans that were longer and had tails,
它们都是由身形细长 有尾巴
with a body plan more like a shrimp or a lobster.
身体构造更像虾或者龙虾的甲壳动物进化而来
And then, for some reason, these animals evolved into things that looked like crabs,
然后 由于某些原因 这些动物经过多次独立进化
independently, over and over again.
逐步进化成螃蟹的样子
They turned into false crabs!!
它们演变成了假蟹类!
Fake!
假的!
Impostors I tell you!
冒名顶替者 我告诉你!
So why does this keep happening?
那么为什么这种情况持续发生呢?
What is it about the crab’s form that makes it so evolutionarily successful —
是有关螃蟹形态的什么 让它进化得如此成功——
so successful that non-crabs are apparently jealous of it?
如此成功以至于非蟹类似乎会嫉妒它?
Well, it might sound odd to say this about an animal with a shell,
这样说有壳动物可能听起来很奇怪
but the answer seems to be that it’s all about flexibility.
但答案似乎是说这一切都与灵活性有关
史前
Crab-like creatures date back to the Late Devonian Period, about 365 million years ago.
类螃蟹生物可以追溯到约3.65亿年前的泥盆纪晚期
And they started with the first decapod crustaceans, like Palaeopalaemon.
从如长臂虾等第一批十足动物开始
Decapods are named for their ten feet, and their order includes things like shrimp, crayfish,
十足目动物因为十只脚而得名 其中包括了虾 小龙虾
lobsters, and crabs — both true and false.
龙虾和螃蟹等——包括真蟹和假蟹
And Palaeopalaemon is the oldest lobster-like decapod ever found,
长臂虾是发现的最古老的像龙虾般的十足动物
and also one of the oldest decapods period.
也是十足动物时期最古老的生物之一
It probably lived on the seafloor, like a modern lobster does
它有可能像现代龙虾一样生活在海底
and may have had specialized feeding appendages
可能还有专门捕食用的附肢
for browsing around in soft seafloor mud.
以便在柔软的海底泥浆中寻找食物
But then, around 260 million years ago, decapods split into two groups —
但随后 在约2.6亿年前 十足动物分为两派
the Anomurans, or those false, fake wanna-be crabs,
异尾下目 或者说是想成为真蟹的假蟹
and the Brachyurans, or the true crabs —
还有短尾下目 或者说是真蟹
the crabs that aren’t lying to you.
没有欺骗你的那种真蟹
The oldest undisputed true crab is Eoprosopon,
公认的最古老的真蟹是Eoprosopon
a crustacean that lived 185 million years ago in the early Jurassic Period.
生活在1.85亿年前的侏罗纪早期的甲壳动物
And, for a while, scientists argued over whether it actually belonged in the crab family,
一段时间以来 科学家们一直在争论它是否真的属于螃蟹科
because it has some un-crab-like traits —
因为它有一些不像螃蟹的特征
like a slightly more elongated abdomen and really prominent antennae.
比如它的腹部更细长 还有突出的触角
But after re-evaluating the only known specimen with new imaging techniques,
然而在使用新的成像技术重新评估了唯一已知的标本后
experts decided that Eoprosopon was a very early member of the Brachyura.
专家们判定Eoprosopon是短尾下目的早期成员
Now, on the other side of the decapod family tree, there’s Platykotta,
在十足类动物家族树的另一侧是platykotta
just a little older than Eoprosopon at about 200 million years old, from the late Triassic Period.
它比Eoprosopon稍早一点 大约来自两亿年前的三叠纪晚期
It’s thought to be the oldest false crab, and it looked more like a lobster.
它被认为是最古老的假蟹 看起来更像龙虾
But over the course of evolutionary time, both the Anomurans and the Brachyurans came
但是在进化过程中 异尾下目和短尾下目都
closer and closer to what we think of as the “crab shape” that we know today.
越来越接近我们所认为的现代螃蟹的形态
In both groups, time and time again, crustaceans started out with the elongated body of a lobster
这两个下目中的甲壳动物屡次从龙虾细长的身形开始
only to evolve into the rounder, flatter shape of a crab.
竟然最后演变成螃蟹更圆 更扁平的形态
And scientists have been trying to figure out why this happens
科学家们在一百多年里一直在
for more than a hundred years.
试图弄清为什么会发生这种情况
One of the first naturalists to recognize this was an English zoologist named
最早认识到这一点的博物学家之一是英国动物学家
Lancelot Alexander Borradaile.
名叫兰斯洛特·亚历山大·博拉代尔
And in 1916 he named the process “carcinization,”
1916年 他把这个过程命名为“蟹化”
which means to become crab-like.
意思是变得像螃蟹一样
And he also described how he thought the process happened.
他还描述了在他看来 这个过程是如何发生的
Basically, the long “tail” of a lobster, called a pleon, grows shorter over time and
基本上 被称为腹部的龙虾的“长尾巴” 随着时间的推移越来越短
gets tucked under the body.
萎缩折叠 藏在身体下方
And, at the same time, the narrow front part of the lobster – the carapace –
同时龙虾的狭窄前部 或者说是头胸甲
grows wider and flatter, until it eventually winds up looking like what we’d call a crab.
变宽变扁平 直到最终看起来像我们所说的螃蟹
OK, but why would these animals repeatedly go from being long and narrow to flat and round?
但是为什么这些动物会反复地从又长又窄变得又平又圆?
Well, back in the 1980s, a study analyzed all of the fossil crustaceans
早在20世纪80年代 一项研究就分析了
throughout the whole Mesozoic Era,
中生代所有化石中的甲壳动物
and discovered that there was an explosion of crab-shaped crustaceans during this span of time.
发现在这段时期中蟹形甲壳动物激增
Another, more recent study found that
另一项更新的研究发现
this phenomenon really took off during the Cretaceous Period,
这种现象在白垩纪时期开始大量出现
which experts sometimes call the Cretaceous Crab Revolution,
专家有时称其为白垩纪螃蟹革命 或者
or, if you prefer, the Mesozoic Decapod Revolution.
如果你喜欢 也可以称之为中生代十足类革命
If you happen to have a band that you’ve started that needs a name
如果你组建的乐队恰好需要一个名字
Both of those are available!
这两个名字都可以使用!
Nearly 80 percent of the major groups of true crabs that we know today
我们今天所知道的将近80%的主要真蟹群
originated in this period.
都起源于这个时期
And throughout the Mesozoic Era, there was a long-term shift
在整个中生代时期 物种长期以来
in diversity toward more crab-shaped species,
一直在向蟹型物种多样化转变
specifically toward true crabs, and away from long-bodied ones.
尤其是向真蟹转变 与长身体的假蟹渐行渐远
The crab-like creatures also seemed to have exploited many more different kinds of habitats
比起它们更多像龙虾的亲戚来说 仿蟹生物似乎能
than their more lobster-y relatives.
利用更多不同类型的栖息地
One possible explanation for this is that their shape allowed for greater mobility.
一种可能的解释是它们的形态使它们有更好的移动性
The rounder, flatter shape of crabs lets crabs walk, run, swim and burrow more efficiently.
螃蟹更圆 更扁平的形态使它们能更高效地走 跑 游和挖洞
There are even crabs that climb tree, which is its own special kind of nightmare fuel!
甚至有螃蟹能爬树 这是它们让噩梦越发恐怖的独特方法
By contrast, animals that are shaped more like lobsters or shrimp are often limited
相比之下 形态更像虾或者龙虾的动物通常会
to just swimming, burrowing, or scuttling on the ground.
被限制于只能在这片水域中游泳 挖洞或疾走
Other researchers say the transformation to a crab shape
其他研究人员说 向螃蟹形态的转化是
was a way for organisms to better evade predators.
生物体更好地逃避捕食者的一种方式
By losing the pleon—that long tail—
由于失去了腹部 也就是长尾巴
they had one less delicious appendage that predators might grab onto.
被捕食者抓住的就可能是不那么美味的蟹腿
So, since the crab shape allowed crustaceans to go more places,
因此 因为蟹形允许甲壳动物走到更多地方
do more things, and evade more predators,
做更多事情 逃避更多捕食者
that shape was selected for over time,
所以这种形态是经过时间自然选择的
and lots of elongated crustaceans came to be shaped like crabs—even if they weren’t crabs.
即使它们不是螃蟹 还是有很多细长的甲壳动物变成了蟹形
But of course, sometimes certain adaptations
当然 有时也会有一些适应性变化
— no matter how helpful they might seem — just don’t stick.
——不管它们看起来多么有用——不要坚持
And, just to keep things interesting! there have been many times when crustaceans lost their crab-like shape!
有趣的是!甲壳动物也曾很多次失去蟹形
This is called, you guessed it, decarcinization.
你猜对了 这叫做去蟹化
This has happened among true crabs, like in a fossil crab called Callichimaera perplexa
这种情况发生在真螃蟹身上 比如化石中的螃蟹Callichimaera Perplexa
Its name means “perplexing beautiful chimera”
它的名字意为“令人迷惑的美丽嵌合体”
and it lived between 95 million and 90 million years ago, during that Cretaceous Crab Revolution thing.
它生活于9500万到9000万年之前的白垩纪螃蟹革命时期
And it kinda looked like a crab, but not totally.
看起来有点像螃蟹 但还不完全像
Its large eyes weren’t on stalks,
它的大眼睛不在眼柄上
it had front limbs shaped kind of like oars,
它的前肢有点像桨
and its body shape wasn’t quite the same as what we normally think of as … crabby.
它的身体形态也不完全像我们通常所认为的螃蟹那样
look at those big adorable eyes!
看那对可爱的大眼睛!
It’s like the Baby Yodaof crabs
类似于现在螃蟹的大眼幼体
All told, the phenomenon of carcinization is
总之 蟹化现象是趋同进化中
one of the more fascinating examples of convergent evolution.
比较吸引人的例子之一
There are a lot of reasons a crustacean might evolve into the shape of a crab,
即使它们不是真螃蟹
even if it’s not actually a crab.
甲壳动物可能进化成蟹形也有很多原因
It allows for a lot of versatility in locomotion and lifestyle.
这种进化考虑到了运动和生活方式的多样性
Today, crabs can clamber around the deep sea, scuttle over beaches,
现在 螃蟹能在深海里爬来爬去 在沙滩上疾走
burrow in the sand, and propel themselves through the water.
在沙子里挖洞 还能推动自己在水中前进
They live in freshwater, salt water, and on land —
它们生活在淡水中 海水中 陆地上
they’re pretty much everywhere, true crabs and false alike.
真蟹与假蟹两者几乎都无处不在
At the end of the day, it’s all about how well an organism can survive in its environment.
归根结底 这都是生物体在该环境中生存的能力有多强
So maybe we can’t blame for false crabs for wanting to be crabs.
也许我们不应该责备想成为螃蟹的假蟹
Just please keep those coconut crabs the heck away from me, forever.
请让那些椰子蟹永远离我远点
Big thanks to this month’s clawsome Eontologists: Sean Dennis, Jake Hart,
非常感谢本月的蟹类研究专家:Sean Dennis Jake Hart
Annie and Eric Higgins, Jon Davison Ng, and Patrick Seifert.
Annie Higgins Eric Higgins Jon Davison Ng以及Patrick Seifert
You can become an Eonite by supporting us at patreon.com/eons.
你可以通过在patreon.com/eons上支持我们而成为赞助者
And remember – Eonites get perks like submitting a joke for us to read!
记住 赞助者有特殊待遇 比如提交一个笑话给大家看
Which I’m going to do right now… this one is from Stephen O’Leary
我现在就要看看 这一条笑话来自于Stephen O’Leary
He says “The Amniotic Egg was egg-sackly what we needed.”
他说“羊膜卵是我们需要的蛋类”
Oh man
天啊
And as always thank you for joining me in the Konstantin Haase studio.
一如既往 感谢您收看Konstantin Haase工作室制作的栏目
If you like what we do here, go to youtube.com/eons and subscribe!
如果你喜欢 请在youtube.com/eons上点击订阅

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视频概述

揭秘螃蟹的进化过程,何为真蟹,何为假蟹?

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视频来源

https://www.youtube.com/watch?v=wvfR3XLXPvw

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