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恐龙有一个吸血的敌人

Dinosaurs Had a Bloodsucking Enemy

[音乐]本周的《科学秀》
♩♩Intro♩♩ This week on SciShow News,
我们来谈谈虫子和脑子
we ’ re talking about bugs and brains.
只不过 不是真正的虫子 只是一些蛛形纲生物
Except… not really true bugs, just somearachnids.
但是“蛛形纲和脑子”听起来并不吸引人 不管怎样
But “arachnids and brains” didn’t soundas catchy. Anyway,
这周在《Nature Communication》上
in a paper published this week
发表的论文表明 科学家找到
in Nature Communications, scientists found two
两条不同的线索告诉我们一些 关于恐龙和他们身上寄生虫的事
separate clues that teach us a little more about dinosaurs and their parasites.
一是 研究人员发现了一种灭绝的扁虱
For one, these researchers discovered an extinct tick entangled
纠缠在一片恐龙的羽毛里
in a piece of a dinosaur feather.
这个样品被封在距今9900万年前
This sample was trapped in a 99-million-year-old chunk
缅甸发现的大块琥珀中
of amber from Myanmar, and dates back
时间可以追溯到白垩纪时期
to the Cretaceous period.
重大的新闻不是发现羽毛本身
The big news here isn’t the feather itself,though.
而是那只扁虱
It’s the tick!
因为 很难找到 已知寄生宿主的扁虱
Because finding ticks preserved with direct evidence of what they fed on is really rare.
事实上 这是已知最古老的样本
In fact, this is the oldest known example.
这一小片羽毛
The bit of feather is
有两厘米长 在上面有多达
about two centimeters long and includes more than 50 barbs along
五十个倒钩
a section of the central shaft.
这和现在鸟的羽毛十分相似
It ’ s pretty similar to modern-day bird feathers,
但是白垩纪时期 很大一部分恐龙
but a whole range of dinosaurs from the Cretaceous
都有这样的羽毛 包括陆生恐龙和很多类似于鸟类的品种
period had feathers like this, including ground-running dinos and more bird-like species.
所以我们不能准确判断 这只寄生虫寄生在哪种恐龙身上
So we don ’ t know exactly what kind of dinosaur the tick was feeding on,
但是
but since this was
这是在现代鸟类诞生之前 我们可以把鸟类排除
before modern birds existed, we can definitelyrule them out.
这种寄生虫不是唯一一种喜爱恐龙血的
And that one species wasn ’ t alone in its taste for dinosaur blood.
这份论文也着眼于另一块
This paper also looked at a separate piece
来自和前面提到的 相同时期的琥珀 间接证明
of amber from the same period, with /indirect/
另一种已经灭绝的生物 也是恐龙的寄生虫
evidence that a different extinct tick wasalso a dinosaur parasite.
由于这种扁虱不全寄生在羽毛中
These ticks weren ’ t all tangled up in feathers,
因此只能通过琥珀间接推测出来
which is why it ’ s indirect evidence.
一只肚子里全是血
One was full of blood,
另一对十分靠近 也被完好地保存下来
and another pair of two ticks were preserved close together.
这一对身上有一些其他的器官
The pair had some other junk on them,
这些头发一样的结构叫刚毛
too — these hair-like structures called setae
这来自于甲壳动物幼虫的皮蠹
that came from larval dermestid beetles.
这种甲壳生物现在依然存在
This family of beetles is still around today and some species
并且 其中一些品种 喜欢去鸟窝
like to hang out in bird nests,
吃掉落的小片羽毛和鸟皮 以及类似的美食
eating stray bits of feathers and skin… all that delicious stuff.
我们知道一些恐龙也筑巢
We know some dinosaurs built nests too,
所以扁虱和甲壳虫 可能
so both the ticks and beetles were probably living
都住在里面 希望饱餐一顿
in one, hoping to score a meal.
研究也表明
The researchers also say
如果两只未进食的扁虱同时呆在一个窝里
that a drip of plant resin would be more likely to trap two unfed
一滴植物的树脂就可以困住它们
ticks at once if they were hanging out in a nest together. But,
但是不会因此诞生侏罗纪公园
Jurassic Park aside,
我们不能通过 古扁虱肚中的血
we won ’ t be able to clone a feathered dinosaur from blood in
就克隆出一只长羽毛的恐龙
any of these old ticks.
没有人能萃取DNA
No one ’ s ever actually extracted DNA
在被封在琥珀的昆虫体内
from insects preserved in amber — there are just
那里只有坏掉的以及已经降解的东西
too many things that can go wrong or breakdown.
所以到目前为止 侏罗纪公园依旧只存在于科幻小说中
So for now, that’s still the stuff of sci-fi.
但我们第二个话题 是时刻发生在人身上的事
But our second topic is something that happens to humans all the time.
看这张照片 你正走在人行道上 当你发现
Picture this: you ’ re walking down the sidewalk when you realize that,
你的脚
right where your foot
即将踩在一堆狗屎上
is about to land, is a pile of dog poop.
你看到狗屎 于是拼命地调整落脚点
You see it there, and you desperately try to adjust,
但是 你知道的 啪
but you know… plop.
你的重心已经降下来 于是就踩上了
You’re weight is going down any way and…it’s happened
但是 一组研究员
But a group of researchers
来自约翰· 霍普金斯大学 可能找到
from Johns Hopkins University may have figured out why it ’ s
当你肢体移动时很难停下的原因
so hard to stop doing something while your body is in motion. Previously,
以前科学家认为
scientists thought that only one region
在大脑指挥肌肉移动之后
of the brain — part of the prefrontal
大脑中只有一个部位
cortex — was involved in sending that last-minute “ stop!
前额皮质
” signal after the brain directs
参与传递最后一刻的“停止”指令
our muscles to move.
但是 现在我们了解到
But now we know
把这个指令发出去 实际需要超快的协调性
that getting this signal out actually requires super-fast coordination
在前额皮质两块不同部位之间
between two different parts of the prefrontal cortex,
加上一部分运动前区皮质
plus part of the premotor cortex.
为了验证这件事
To figure this out,
科学家给21个人以及一只猕猴 几乎相同的实验
scientists gave 21 human subjects and one macaque monkey mostly similar
并观察他们的脑子在做什么
tasks while taking a peek at what their brainswere doing.
人脑活动
The humans had their brain activity monitored
由用来常检测血液流动的 功能磁共振成像监控着
with fMRI, which measures general blood flow patterns.
而猴子们的脑子中被植入了 用来监测神经元活动的电极
And the monkey had electrodes implanted in its brain to monitor some individual neurons.
我们不会把这用在人身上
We didn’t do that to the people…
因为 我们不想切开他们的脑袋
because we didn’t want to cut their brains open.
在实验过程中
In the main test,
被试者将看见屏幕上的一幅图
the subjects saw one of two shapes on a computer screen, which told
这幅图告诉他们 蓝色意味着走 黄色意味着停
them whether blue was going to mean go and yellow was going to mean stop,
或是反过来 然后
or vice versa. Then,
一个黑色圆环会突然出现
a black circle would pop up,
参与实验者会很快
and the study participants would quickly move their
转眼看去
eyes to look at it.
但是 如果一个蓝色或黄色圆点出现
But if a blue or yellow dot appeared,
根据第一幅图的颜色和代表的指令 他们会停下或继续走
they would have to either stop or keep going with
并让视线跟随图像移动
their eye movement, depending on that initialshape and its meaning.
以往实验会用一个更简单的测试
A previous version of this experiment useda simpler task.
但是 运用新的方法
But doing it this way let
让研究员能判断 发出信号的不同部位
the researchers estimate signals related to different parts
比如说参与者注视屏幕上的形状时
of it, like watching for the shape
以及大脑传递停止命令时
on the screen versus sending the message to stop motion.
数据表明一部分
The data suggest that one part
前额皮质 识别并翻译了指令
of the prefrontal cortex identifies and interprets information signals,
另一部分 发出停止动作的指令
and another part registers the intentto stop the motion.
两块区域看起来
Both regions seem to coordinate
和运动前区皮质区一起配合
with another brain region in the premotor cortex, which
控制视线移动
controls the eye movement.
而他们是否成功地停下 取决于调控的速度
And whether they successfully stopped or not depended on the timing.
研究员估算说
The researchers calculated that
如果被试者的反应速度超过
if a subject ’ s decision took more than about a quarter of
四分之一秒 那么最初的
a second, then the original “ move!
“前进”指令就会到达肌肉
” signal was already on its way to the muscles and
动作也就不能停止了
couldn’t be changed or stopped.
他们也表明 这会有助于解释
They even suggest that this could help explain
为什么人们会总是摔倒
why people might stumble more as they get
当他们老了——老化的大脑 传递信息速度会更慢
older — aging brains communicate more slowly,
所以当他们起立时
so they might not be able to put on the brakes
总是站不稳 但是
as easily when they need to. But,
一如既往 剩下还有很多实验要做
as always, there’s a lot more researchleft to do.
感谢你收看这一期的《科学秀》
Thanks for watching this episode of SciShow News,
尤其感谢所有
and thanks especially to all of our
众筹网站上的赞助人 是他们成就了这个节目
patrons on Patreon who make this show possible.
如果你想要支持我们继续做视频
If you want to help us keep making videos
像这样 像所有人免费开放
like this for the whole world for free, you
你可以访问patreon.com/scishow
can go to patreon.com/scishow­.
不要忘记去youtube.com/scishow订阅本栏目
And don’t forget to go to youtube.com/scishowand subscribe!
完[音乐]
♩♩Outro♩♩

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视频概述

本期的节目将会为你解开,恐龙身上寄生虫的秘密,凭借寄生虫吸食的血能否创造出一个侏罗纪公园?当然,也会向你介绍人体的奥秘,当你走在路上,看见你的脚即将踩上一坨狗屎,是什么阻止了你将你的脚顺利移开?欢迎收看本期的SciShow!

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视频来源

https://www.youtube.com/watch?v=KOkZwj-uMtE

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