Ed Yong: Suicidal wasps, zombie roaches and other parasite tales

譯者: YS Tsai 審譯者: 杏儀 歐陽

A herd of wildebeests, a shoal of fish,

一群牛羚, 一群魚, 和一群飛鳥

a flock of birds.

Many animals gather in large groups

很多動物都喜歡集結成群

that are among the most wonderful spectacles

這是自然界中最美妙的一件事

in the natural world.

But why do these groups form?

但是為什麼要成群結隊呢?

The common answers include things like

最常見的說法是

seeking safety in numbers or hunting in packs

為了安全或方便狩獵, 又或者交配與繁殖,

or gathering to mate or breed,

and all of these explanations,

以上的這些解釋,

while often true,

通常都是正確的,

make a huge assumption about animal behavior,

這些都是人類對於 動物們在行為上的假設

that the animals are in control of their own actions,

這些動物們可以控制牠們的行為

that they are in charge of their bodies.

並對自己的身體負責

And that is often not the case.

但是通常卻不是這麼一回事

This is Artemia, a brine shrimp.

這是豐年蝦 (鹵蟲), 一種鹽水蝦

You probably know it better as a sea monkey.

又常被稱之為 ”海猴子“

It's small, and it typically lives alone,

牠非常的小, 通常習慣獨居

but it can gather in these large red swarms

但是牠也可以集結成 像這一大片的紅色群體

that span for meters,

大到足以用公尺(米)為單位來計算

and these form because of a parasite.

這些豐年蝦之所以聚集,是因為寄生蟲

These shrimp are infected with a tapeworm.

這些蝦子都被 “絛蟲” 給感染了

A tapeworm is effectively a long, living gut

絛蟲 (寄生蟲) 實際上就像是 一條既長又活生生的腸子

with genitals at one end and a hooked mouth at the other.

一端是生殖器, 另一端是帶鉤的口腔

As a freelance journalist, I sympathize.

身為一個自由的撰稿人, 我很同情牠

(Laughter)

(群眾笑聲)

The tapeworm drains nutrients from Artemia's body,

絛蟲吸附在豐年蝦的身上 並吸取牠的養分,

but it also does other things.

不止這樣, 絛蟲還做了另外一件事

It castrates them,

絛蟲閹割了這些豐年蝦

it changes their color from transparent to bright red,

絛蟲把這些豐年蝦從本身的 透明色轉變成了亮紅色,

it makes them live longer,

絛蟲讓這些豐年蝦活得更久,

and as biologist Nicolas Rode has found,

生物學家尼可拉斯.羅得發現

it makes them swim in groups.

寄生的絛蟲讓這些 原本獨居的蝦集結在一起

Why? Because the tapeworm, like many other parasites,

為什麼呢? 因為這些絛蟲 就像是其他的寄生物種一樣,

has a complicated life cycle

有著複雜的生活形態

involving many different hosts.

擁有很多不同的宿主

The shrimp are just one step on its journey.

寄生在這些蝦身上只是 這些絛蟲旅程的第一步

Its ultimate destination is this,

牠們的最終目的是這個,

the greater flamingo.

大紅鶴

Only in a flamingo can the tapeworm reproduce,

只有在紅鶴身上, 這些絛蟲才得以繁衍

so to get there, it manipulates its shrimp hosts

所以為了要達到目的, 絛蟲只能先行操縱蝦子宿主

into forming these conspicuous colored swarms

進而形成這些顯眼的紅色蝦群

that are easier for a flamingo to spot

這樣才能更輕易地吸引紅鶴的注意

and to devour,

並獵捕吞食,

and that is the secret of the Artemia swarm.

而這就是豐年蝦群集的秘密.

They aren't sociable through their own volition,

豐年蝦並不是依 自身意志組成的群居動物

but because they are being controlled.

而是因為豐年蝦被控制了

It's not safety in numbers.

群體生活看似無法提供安全感

It's actually the exact opposite.

實際上卻剛好相反

The tapeworm hijacks their brains and their bodies,

絛蟲入侵了這些 豐年蝦的大腦與身體,

turning them into vehicles

並把這些豐年蝦當作

for getting itself into a flamingo.

進入紅鶴體內的一項交通工具

And here is another example

這裡還有另外一個

of a parasitic manipulation.

寄生蟲操縱宿主的案例

This is a suicidal cricket.

這是一隻具自殺傾向的蟋蟀

This cricket swallowed the larvae of a Gordian worm,

這隻蟋蟀吞食了鐵線蟲的幼蟲,

or horsehair worm.

鐵線蟲又名馬鬃蟲

The worm grew to adult size within it,

蟲子會在蟋蟀身體裡長到成蟲,

but it needs to get into water in order to mate,

但是牠(鐵線蟲)必須在水裡交配,

and it does that by releasing proteins

當鐵線蟲需要交配時 就會分泌特殊蛋白質

that addle the cricket's brain,

腐蝕蟋蟀的大腦,

causing it to behave erratically.

造成蟋蟀行為失常.

When the cricket nears a body of water,

當蟋蟀靠近水邊的時候,

such as this swimming pool,

例如這個游泳池邊,

it jumps in and drowns,

牠就會跳入水裡並淹死自己,

and the worm wriggles out

這時鐵線蟲就會

of its suicidal corpse.

從死屍裡蠕動而出.

Crickets are really roomy. Who knew?

蟋蟀體內很寬敞. 但是誰知道呢?

The tapeworm and the Gordian worm are not alone.

絛蟲和鐵線蟲並不孤單

They are part of an entire cavalcade

牠們是控制大腦的

of mind-controlling parasites,

寄生蟲軍團的一份子

of fungi, viruses, and worms and insects and more

像是真菌, 病毒, 蠕蟲, 昆蟲等等

that all specialize in subverting and overriding

這些都是擅長攪亂及重寫

the wills of their hosts.

宿主們本身意願的寄生體

Now, I first learned about this way of life

當我約20年前第一次

through David Attenborough's "Trials of Life"

從大衛·阿滕伯勒的書 《生命的征途》上

about 20 years ago,

學習到這種生物形態

and then later through a wonderful book called

再從另一本非常好的書

"Parasite Rex" by my friend Carl Zimmer.

由我朋友卡爾·齊默 撰寫的《霸王寄生蟲》上見到

And I've been writing about these creatures ever since.

之後我就以這些生物 為主題不停地寫作至今

Few topics in biology enthrall me more.

還有一些生物學的主題令我更加著迷

It's like the parasites have subverted my own brain.

這感覺就像是這些 寄生蟲已經竄改了我的大腦

Because after all, they are always compelling

因為畢竟, 牠們是如此地引人注目

and they are delightfully macabre.

卻又同時令人感到毛骨悚然

When you write about parasites,

當你在寫關於寄生蟲的文章時,

your lexicon swells with phrases like

你的詞彙量張嘴就是 "活活吞噬"

"devoured alive" and "bursts out of its body."

閉口就是 “衝出身體”。

(Laughter)

(群眾笑聲)

But there's more to it than that.

不僅如此

I'm a writer, and fellow writers in the audience

我是個作家, 觀眾席裡有些人也是作家

will know that we love stories.

作家都知道每個人都喜歡故事

Parasites invite us to resist the allure

寄生蟲讓我們拒絕撰寫那些

of obvious stories.

淺顯易見的故事情節的誘惑

Their world is one of plot twists

牠們生存的世界是劇情的轉折點之一

and unexpected explanations.

也是無法預測的解釋

Why, for example,

為什麼? 例如,

does this caterpillar

這隻毛毛蟲

start violently thrashing about

當其他昆蟲靠近牠

when another insect gets close to it

和那些白色蟲繭的時候

and those white cocoons that it seems

毛毛蟲是在開始激烈反抗嗎？

to be standing guard over?

毛毛蟲貌似在站崗護衛這些繭

Is it maybe protecting its siblings?

難道毛毛蟲在保護牠的兄弟姐妹嗎?

No.

不是的

This caterpillar was attacked

這隻毛毛蟲是被寄生蜂給攻擊

by a parasitic wasp which laid eggs inside it.

並被體內產卵

The eggs hatched and the young wasps

寄生蜂的蛋將孵化在 毛毛蟲的體內,

devoured the caterpillar alive

而這隻寄生蜂幼蟲 在衝破毛毛蟲的身體之前

before bursting out of its body.

將毛毛蟲從內部活活吞食

See what I mean?

你們了解我的意思了嗎?

Now, the caterpillar didn't die.

然而, 這隻毛毛蟲還在苟延殘喘

Some of the wasps seemed to stay behind

有些寄生蜂卻背後

and controlled it into defending their siblings

控制著這只毛毛蟲

保護自己的兄弟姐妹

which are metamorphosing

直到牠們在繭內破繭成蟲

into adults within those cocoons.

This caterpillar is a head-banging zombie bodyguard

這隻毛毛蟲只是一隻 搖頭晃腦的殭屍保鏢

defending the offspring

保護著那些殺死自己的

of the creature that killed it.

生物的後代(寄生蜂的後代)

(Applause)

(群眾掌聲)

We have a lot to get through. I only have 13 minutes. (Laughter)

我們還有很多要說, 而我只有13分鐘 (群眾笑聲)

Now, some of you are probably just

現在, 你們有些人可能

desperately clawing for some solace

只是拼命地尋求一些慰藉

in the idea that these things are oddities

說這些都只是自然界裡的怪事,

of the natural world, that they are outliers,

這些發生的事情都是離群值,

and that point of view is understandable,

這些論點都是可被理解的,

because by their nature, parasites are quite small

因為牠們的天性, 寄生體是很小的

and they spend a lot of their time

牠們花費很多的時間

inside the bodies of other things.

在別的物種身上

They're easy to overlook,

牠們很容易被小看,

but that doesn't mean that they aren't important.

但是這不代表牠們不重要

A few years back, a man called Kevin Lafferty

幾年前, 有個名叫凱文·拉弗蒂的人

took a group of scientists into three Californian estuaries

帶了一群科學家去了加州的三個河口

and they pretty much weighed and dissected

他們幾乎將能找到的所有東西

and recorded everything they could find,

通通稱重, 解剖, 及記錄了下來,

and what they found

他們發現

were parasites in extreme abundance.

寄生物種非常豐富多元

Especially common were trematodes,

尤其是吸蟲類最為常見,

tiny worms that specialize in castrating their hosts

牠們(吸蟲)是專門閹割宿主的微小蠕蟲

like this unfortunate snail.

好比這隻不幸的蝸牛

Now, a single trematode is tiny, microscopic,

現在, 單一隻吸蟲是十分微小的, 僅能依靠顯微鏡觀測

but collectively they weighed as much

但是全體加起來的重量就和

as all the fish in the estuaries

河口裡所有的魚一樣重

and three to nine times more than all the birds.

或者是所有鳥類總重的三到九倍之多

And remember the Gordian worm that I showed you,

還記得我剛才給你們看的鐵線蟲

the cricket thing?

和那隻蟋蟀嗎?

One Japanese scientist called Takuya Sato

有個名叫佐藤拓也的日本科學家

found that in one stream,

在一段河流裡發現

these things drive so many crickets

這些寄生蟲控制著很多的蟋蟀

and grasshoppers into the water

和蚱蜢跳入水中

that the drowned insects

進而淹死這些昆蟲

make up some 60 percent of the diet of local trout.

而這些昆蟲占了當地鱒魚60%的食物來源

Manipulation is not an oddity.

這些操控並不是奇怪的事

It is a critical and common part

這是發生在我們週遭, 很複雜

of the world around us,

卻又平常的世界的一部份

and scientists have now found

科學家目前發現了

hundreds of examples of such manipulators,

數百種這類型的案例,

and more excitingly, they're starting to understand

更令人振奮的是, 科學家們開始了解

exactly how these creatures control their hosts.

這些寄生體到底是 怎麼控制牠們宿主的

And this is one of my favorite examples.

這是我最喜歡的案例之一

This is Ampulex compressa,

這是安瓿牛鞭

the emerald cockroach wasp,

也叫扁頭泥蜂

and it is a truth universally acknowledged

還有件眾所皆知的事

that an emerald cockroach wasp in possession

就是這些扁頭泥蜂

of some fertilized eggs

會自己的卵

must be in want of a cockroach.

產在蟑螂的身上

When she finds one,

當牠(扁頭泥蜂)找到一隻(蟑螂)時

she stabs it with a stinger

牠(扁頭泥蜂)用牠的刺來叮螫蟑螂

that is also a sense organ.

而刺同時也是牠的感覺器官

This discovery came out three weeks ago.

這些都是三個禮拜前的新發現

She stabs it with a stinger that is a sense organ

牠(扁頭泥蜂)的刺, 也就是牠的感覺器官

equipped with small sensory bumps

有著細小的感官突起物

that allow her to feel the distinctive texture

這些突起物可以讓牠感受到

of a roach's brain.

蟑螂大腦組織的特殊質地

So like a person blindly rooting about in a bag,

就像是一個人盲目的 在一個袋子裡尋找,

she finds the brain, and she injects it with venom

當扁頭泥蜂找到大腦時, 會將毒液注進

into two very specific clusters of neurons.

兩種特定的神經元叢

Israeli scientists Frederic Libersat and Ram Gal

以色列的科學家, 弗雷德里克.李伯賽及拉姆.加爾

found that the venom is a very specific chemical weapon.

發現這些毒液是一種特定的化學武器

It doesn't kill the roach, nor does it sedate it.

這種毒液並不會殺死蟑螂, 也不會對蟑螂產生鎮靜效果

The roach could walk away

蟑螂還是可以離開

or fly or run if it chose to,

或是飛走, 如果蟑螂可以決定的話

but it doesn't choose to,

但是其實蟑螂並不能真正做這個決定,

because the venom nixes its motivation to walk,

因為這些毒液阻斷了蟑螂的行動意願

and only that.

而也就只是這樣

The wasp basically un-checks the escape-from-danger box

基本上這些蜂類讓蟑螂

喪失了逃生本能,

in the roach's operating system,

讓扁頭泥蜂帶著無助的受害者(蟑螂)

allowing her to lead her helpless victim

back to her lair by its antennae

藉由觸角回到巢穴內

like a person walking a dog.

就像是人在遛著狗一樣

And once there, she lays an egg on it,

再重複一次, 牠將蛋產在蟑螂上,

egg hatches, devoured alive, bursts out of body,

蛋孵化, 幼蟲將蟑螂活活吞食, 再從牠身體裡破出,

yadda yadda yadda, you know the drill.

如此之類的, 你們已經知道過程了

(Laughter) (Applause)

(群眾笑聲, 掌聲)

Now I would argue that, once stung,

現在我認為, 一次叮螫後

the cockroach isn't a roach anymore.

蟑螂不再是一隻蟑螂

It's more of an extension of the wasp,

而是泥蜂的延伸體,

just like the cricket was an extension of the Gordian worm.

就像是蟋蟀是鐵線蟲的延伸體一樣

These hosts won't get to survive or reproduce.

這些宿主失去了生存及生育的權利

They have as much control over their own fates

牠們對於自身命運的掌控

as my car.

如同我順利掌控我的車一樣.

Once the parasites get in,

一旦寄生體侵入時,

the hosts don't get a say.

宿主便失去了發言權

Now humans, of course,

當然, 現在的人類

are no stranger to manipulation.

對操控並不陌生

We take drugs to shift the chemistries of our brains

我們吸毒來改變大腦的化學物質

and to change our moods,

和改變我們的情緒,

and what are arguments or advertising or big ideas

我們如果沒有打算 要影響別人的意志

if not an attempt to influence someone else's mind?

那所謂的論點、廣告 又或者是偉大的構想又是什麼

But our attempts at doing this

但是我們所做的這些嘗試

are crude and blundering compared

和寄生蟲這種精密又特異的生物比較

to the fine-grained specificity of the parasites.

顯得十分粗糙、亂來

Don Draper only wishes he was as elegant

好比唐.德雷珀只希望他和

and precise as the emerald cockroach wasp.

扁頭泥蜂一樣這麼的高貴和準確

Now, I think this is part of what makes parasites

我認為這是寄生體之所以

so sinister and so compelling.

如此邪惡又卻引人注目的部分原因

We place such a premium on our free will

我們相當注重我們的自由意志

and our independence

和我們的自主權

that the prospect of losing those qualities

當我們失去這些特質後

to forces unseen

將會有看不見的力量

informs many of our deepest societal fears.

將我們最深的社會恐懼呈現出來

Orwellian dystopias and shadowy cabals

奧威爾的 “反烏托邦”和 “影子陰謀”

and mind-controlling supervillains --

還有控制大腦的超級惡棍們

these are tropes that fill our darkest fiction,

都彷彿是暗黑小說中會出現的比喻,

but in nature, they happen all the time.

但是卻無時無刻地 真實發生在自然界中

Which leads me to an obvious

這將我帶到一個明顯

and disquieting question:

又令人不安的問題上:

Are there dark, sinister parasites

是否有一些陰險的寄生蟲

that are influencing our behavior

在我們毫不知情的情況下

without us knowing about it,

影響著我們的日常行為——

besides the NSA?

除了國家安全局(NSA)?

If there are any —

如果有的話--

(Laughter) (Applause)

(群眾笑聲, 掌聲)

I've got a red dot on my forehead now, don't I?

我現在額頭上是不是多了個紅點? (被當成了靶)

(Laughter)

(群眾笑聲)

If there are any, this is a good candidate for them.

如果有的話, 這樣會是牠們很好的候選人

This is Toxoplasma gondii, or Toxo, for short,

這是弓型蟲又稱弓漿蟲, 簡稱為弓蟲

because the terrifying creature

這麼叫牠

always deserves a cute nickname.

是因為令人害怕的物種 通常都有可愛的暱稱

Toxo infects mammals,

弓蟲會感染哺乳類動物,

a wide variety of mammals,

各個品種的哺乳動物,

but it can only sexually reproduce in a cat.

但是牠(弓蟲)卻只能在 貓的身體裡進行有性繁殖

And scientists like Joanne Webster have shown that

科學家像是喬安妮.韋伯斯特證明了

if Toxo gets into a rat or a mouse,

一旦弓蟲進入鼠類當中,

it turns the rodent into a cat-seeking missile.

將會把這些被感染的鼠類 化作尋找貓咪的導彈

If the infected rat smells the delightful odor

如果被感染的鼠類聞到了

of cat piss,

貓咪尿液這樣吸引人的味道

it runs towards the source of the smell

牠(鼠類)就會反常的奔往這味道的方向

rather than the more sensible direction of away.

而不是一如往常地逃離

The cat eats the rat. Toxo gets to have sex.

當這些貓吃了這些鼠類, 弓蟲就得以完成交配

It's a classic tale of Eat, Prey, Love.

這就像是經典的故事模式：吃, 祈禱, 和愛

(Laughter) (Applause)

(群眾笑聲, 掌聲)

You're very charitable, generous people.

你們是非常寬容又慷慨的人

Hi, Elizabeth, I loved your talk.

嗨, 伊麗莎白, 我喜歡你的演說

How does the parasite control its host

寄生蟲是用什麼方法

in this way?

控制著牠的宿主們?

We don't really know.

我們其實不是很知道原因

We know that Toxo releases an enzyme

我們知道弓蟲會釋放某種酶

that makes dopamine, a substance involved

製造多巴胺, 一種活化 大腦獎賞機制及創造動力

in reward and motivation.

的神經傳導物質

We know it targets certain parts of a rodent's brain,

我們知道牠(弓蟲)的目標是 囓齒動物大腦的特定部份,

including those involved in sexual arousal.

包括喚起性慾的部分

But how those puzzle pieces fit together

但是卻不清楚這些片段的認知

is not immediately clear.

能夠怎麼樣被拼在一起

What is clear is that this thing

但有樣認知是明確的,

is a single cell.

那就是, 這個不明物是單細胞

This has no nervous system.

沒有神經系統

It has no consciousness.

也沒有認知能力

It doesn't even have a body.

甚至連個身體都沒有

But it's manipulating a mammal?

但是牠卻可以操控一隻哺乳動物?

We are mammals.

我們就是哺乳類動物

We are more intelligent than a mere rat, to be sure,

想當然爾, 我們是比一隻 單純的老鼠有智慧的多,

but our brains have the same basic structure,

但是我們的大腦有著一樣的基本結構,

the same types of cells,

一樣的細胞,

the same chemicals running through them,

一樣的化學物質在裡頭遊走,

and the same parasites.

和一樣的寄生體

Estimates vary a lot, but some figures suggest

統計上估計的變異程度十分顯著, 但有些數據顯示

that one in three people around the world

全世界每三個人之中

have Toxo in their brains.

就有一個人的大腦裡寄生著弓蟲

Now typically, this doesn't lead to any overt illness.

通常，這並不產生任何明顯的疾病

The parasite holds up in a dormant state

這些寄生體處於

for a long period of time.

長期休眠狀態

But there's some evidence that those people

但有證據顯示那些作為寄生載體的人

who are carriers score slightly differently

在性格問卷上的分數呈現

on personality questionnaires than other people,

和其他人相比會稍加不同

that they have a slightly higher risk of car accidents,

他們車禍發生的風險會稍高

and there's some evidence that people with schizophrenia

此外, 也有證據顯示精神分裂症的患者

are more likely to be infected.

較容易被寄生體感染

Now, I think this evidence is still inconclusive,

我認為這部分的證據目前尚未定論

and even among Toxo researchers,

即使是弓形蟲的研究人員

opinion is divided as to whether the parasite

他們對於弓形蟲是否真正影響人類行為

is truly influencing our behavior.

的意見也彼此分歧

But given the widespread nature of such manipulations,

但由於自然界中充斥著各種操縱模式

it would be completely implausible

人類成為生物中唯一

for humans to be the only species

不會受到相似模式感染的這個論點

that weren't similarly affected.

是完全難以置信的

And I think that this capacity to constantly

我認為這種思維模式不斷地

subvert our way of thinking about the world

顛覆我們對於整個世界的認知

makes parasites amazing.

讓寄生體的存在變得更加驚人

They're constantly inviting us to look at the natural world sideways,

牠們持續地邀請我們 一同看看自然界的橫盤交錯

and to ask if the behaviors we're seeing,

並讓我們反思觀測得來的行為模式

whether they're simple and obvious

無論是淺顯的、

or baffling and puzzling,

莫名其妙的或是令人匪夷所思的

are not the results of individuals

都不是個體行為

acting through their own accord

自願下所產生的

but because they are being bent

而是因為他們被迫

to the control of something else.

服從其他生物的控制

And while that idea may be disquieting,

雖然這個想法可能讓人感到不安

and while parasites' habits may be very grisly,

寄生體的生活模式可能非常可怕

I think that ability to surprise us

但我認為就是這個能力讓我們感到驚訝

makes them as wonderful and as charismatic

讓牠們彷彿熊貓、蝴蝶或海豚這類的生物

as any panda or butterfly or dolphin.

一樣充滿精采與魅力

At the end of "On the Origin of Species,"

在《物種起源》一書的結尾

Charles Darwin writes about the grandeur of life,

達爾文寫到生命的偉大

and of endless forms most beautiful

永無止盡的形式的美麗

and most wonderful,

也是最美好的,

and I like to think he could easily have been talking

我認為他可以很輕鬆的說

about a tapeworm that makes shrimp sociable

絛蟲增加了蝦子社交的技巧

or a wasp that takes cockroaches for walks.

或是寄生蜂牽著蟑螂一同散步

But perhaps, that's just a parasite talking.

但又或許, 這只是寄生蟲在演說

Thank you.

謝謝

(Applause)

(群眾掌聲)