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  • Which of these entities has evolved the ability

    在這些個體當中,誰已經演化出

  • to manipulate an animal many times its size?

    可以操控大於自己好幾倍的生物的能力?

  • The answer is all of them.

    答案是全部都有這種能力

  • These are all parasites,

    這些生物都是寄生蟲

  • organisms that live on or inside another host organism,

    牠們寄生在另一個生物體身上或是體內

  • which they harm and sometimes even kill.

    傷害宿主甚至使宿主死亡

  • Parasite's survival depends on transmitting from one host to the next,

    寄生蟲有時會透過中間物種,從一個宿主傳送到另一個宿主

  • sometimes through an intermediate species.

    而得以存活下來

  • Our parasites elegantly achieve this by manipulating their host's behavior,

    寄生蟲藉由操控宿主的行為優雅地達成這一點

  • sometimes through direct brain hijacking.

    有時會直接劫持大腦

  • For example, this is the Gordian worm.

    舉個例子,這是隻鐵線蟲

  • One of its hosts, this cricket.

    牠會寄生的其中一個宿主是蟋蟀

  • The Gordian worm needs water to mate, but the cricket prefers dry land.

    鐵線蟲需要水來進行交配,但是蟋蟀喜歡乾燥的陸地

  • So once it's big enough to reproduce,

    一旦鐵線蟲到了繁殖時期

  • the worm produces proteins that garble the cricket's navigational system.

    牠會產生一種蛋白質,以竄改蟋蟀的導航系統

  • The confused cricket jumps around erratically,

    受到干擾的蟋蟀就會到處亂跳

  • moves closer to water,

    接近水源

  • and eventually leaps in, often drowning in the process.

    最後跳入水中,通常都會溺斃

  • The worm then wriggles out to mate

    鐵線蟲接著從蟋蟀身體鑽出以在水中繁殖

  • and its eggs get eaten by little water insects

    牠的卵被水中小型昆蟲吞噬

  • that mature,

    接著逐漸成長

  • colonize land,

    登陸

  • and are, in turn, eaten by new crickets.

    接著再被別的蟋蟀獵捕

  • And thus, the Gordian worm lives on.

    如此一來,鐵線蟲就得以一直生存下去

  • And here's the rabies virus, another mind-altering parasite.

    這是狂犬病病毒,另一種能改變宿主心智的寄生蟲

  • This virus infects mammals, often dogs,

    這種病毒會感染哺乳類,通常是狗

  • and travels up the animal's nerves to its brain

    牠們經由動物的神經進入大腦

  • where it causes inflammation that eventually kills the host.

    使其發炎,最後使宿主死亡

  • But before it does, it often increases its host's aggressiveness

    但在這之前,狂犬病毒往往會增加宿主的攻擊性

  • and ramps up the production of rabies-transmitting saliva,

    並使宿主大量產生會傳遞狂犬病的唾液

  • while making it hard to swallow.

    增加唾液的同時也讓宿主難以吞嚥

  • These factors make the host more likely to bite another animal

    綜合以上因素讓宿主更有可能攻擊其他動物

  • and more likely to pass the virus on when it does.

    與此同時也更容易傳播狂犬病

  • And now, meet Ophiocordyceps, also known as the zombie fungus.

    現在來看看偏側蛇蟲草菌,又稱為殭屍真菌

  • Its host of choice is tropical ants that normally live in treetops.

    牠所選擇的宿主是熱帶螞蟻,通常住在樹梢上

  • After Ophiocordyceps' spores pierce the ant's exoskeleton,

    偏側蛇蟲草菌的孢子刺穿螞蟻的外骨骼後

  • they set off convulsions that make the ant fall from the tree.

    會使螞蟻抽搐並從樹上跌落

  • The fungus changes the ant's behavior, compelling it to wander mindlessly

    這種真菌會改變螞蟻的行為舉止,迫使螞蟻盲目地流浪

  • until it stumbles onto a plant leaf with the perfect fungal breeding conditions,

    直到螞蟻發現非常適合真菌繁殖的葉子

  • which it latches onto.

    螞蟻就會緊緊抓住葉子

  • The ant then dies,

    接著螞蟻死去

  • and the fungus parasitizes its body to build a tall, thin stalk from its neck.

    真菌會從螞蟻的脖子長出一根細長的莖

  • Within several weeks, the stalk shoots off spores,

    不超過數周的時間,這根莖會散播孢子

  • which turn more ants into six-legged leaf-seeking zombies.

    孢子就會將更多的螞蟻變成尋找葉子的六腳殭屍

  • One of humanity's most deadly assailants is a behavior-altering parasite,

    其中一個對人類最具殺傷力的生物,是一種可以改變宿主行為的寄生蟲

  • though if it's any consolation,

    令人安慰的是

  • it's not our brains that are being hijacked.

    牠控制的不是我們的大腦

  • I'm talking about Plasmodium, which causes malaria.

    我現在說的是瘧原蟲,是造成瘧疾的寄生蟲

  • This parasite needs mosquitoes to shuttle it between hosts,

    這種寄生蟲需要蚊子來讓牠穿梭於宿主之間

  • so it makes them bite more frequently and for longer.

    牠會使蚊子叮咬得更頻繁、更持久

  • There's also evidence that humans infected with malaria

    有證據顯示,感染瘧疾的人類

  • are more attractive to mosquitoes,

    對於蚊子來說更有吸引力

  • which will bite them and transfer the parasite further.

    使得蚊子叮咬他們,並進一步傳播瘧原蟲

  • This multi-species system is so effective,

    這種多物種間傳遞的方法相當有效

  • that there are hundreds of millions of malaria cases every year.

    每年都有數以百萬計的瘧疾病例

  • And finally, there are cats.

    最後一個例子,貓

  • Don't worry, there probably aren't any cats living in your body

    別擔心,應該不會有貓住在你的身體裡

  • and controlling your thoughts.

    或是控制你的思想

  • I mean, probably.

    我的意思是,有可能

  • But there is a microorganism called Toxoplasma

    但有一種稱作弓蟲的微生物

  • that needs both cats and rodents to complete its life cycle.

    需要貓和老鼠來完成牠的生命週期

  • When a rat gets infected by eating cat feces,

    當老鼠吃了貓的排泄物而遭到感染

  • the parasite changes chemical levels in the rat's brain,

    弓蟲會改變老鼠大腦裡的化學物質濃度

  • making it less cautious around the hungry felines,

    讓老鼠對飢餓的貓變得較不警戒

  • maybe even attracted to them.

    甚至使老鼠接近貓

  • This makes them easy prey,

    這就讓老鼠輕而易舉地變成了獵物

  • so these infected rodents get eaten and pass the parasite on.

    遭感染的老鼠被吃掉後,寄生蟲就繼續傳染到下個宿主

  • Mind control successful.

    洗腦成功

  • There's even evidence that the parasite affects human behavior.

    甚至有證據顯示,這種寄生蟲能影響人類行為

  • In most cases, we don't completely understand

    在大多數的案例中,我們並沒有完全了解

  • how these parasites manage their feats of behavior modification.

    這些寄生蟲是如何改變生物的行為舉止

  • But from what we do know,

    但根據我們所知道的

  • we can tell that they have a pretty diverse toolbox.

    我們可以發現寄生蟲有很多樣的工具

  • Gordian worms seem to affect crickets' brains directly.

    鐵線蟲似乎能直接影響蟋蟀的大腦

  • The malaria parasite, on the other hand,

    瘧原蟲則是

  • blocks an enzyme that helps the mosquitoes feed,

    阻擋了有助於蚊子吸血的酵素

  • forcing them to bite over and over and over again.

    迫使蚊子一而再,再而三的叮咬

  • The rabies virus may cause that snarling, slobbering behavior

    狂犬病病毒藉由讓免疫系統過度反應

  • by putting the immune system into overdrive.

    而使得宿主吠叫和流口水

  • But whatever the method,

    不管方法為何

  • when you think about how effectively

    一想到這些寄生蟲

  • these parasites control the behavior of their hosts,

    是多麼有效地控制著他們的宿主

  • you may wonder how much of human behavior is actually parasites doing the talking.

    你可能會想著,不知道多少人類的行為,都實際上是寄生蟲在控制

  • Since more than half of the species on Earth are parasites,

    由於地球上一半以上的物種都是寄生蟲

  • it could be more than we think.

    牠們所能做的可能超乎我們想像

Which of these entities has evolved the ability

在這些個體當中,誰已經演化出

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B2 中高級 中文 TED-Ed 宿主 寄生蟲 螞蟻 蟋蟀 蚊子

【TED-Ed】大腦寄生蟲如何改變宿主的行為--Jaap de Roode。 (【TED-Ed】How brain parasites change their host's behavior - Jaap de Roode)

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    CUChou 發佈於 2021 年 01 月 14 日
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