06:21
TEDYouth 2014

Jaap de Roode: How butterflies self-medicate

ジャープ・デ=ローデ: 自ら治療する蝶

Filmed:

私たち人間と同じように、オオカバマダラも時には寄生虫によって病におかされます。ところが、生物学者のジャープ・デ=ローデは自身が研究していた蝶について面白い発見をします。寄生虫に感染したメスの母蝶が産卵場所に選んだのは、子どもを病気から避けることができる特別な薬草の上だったのです。なぜこの薬草を選ぶことができるのでしょうか?これを「バタフライ効果」として考えてみましょう。人間の病気を治療できる新しい薬の開発のヒントになるかもしれません。

- Biologist
Jaap de Roode studies the ecology and evolution of parasites, focusing on those that attack the monarch butterfly. Full bio

感染症とは
00:12
So infectious diseases, right?
00:13
Infectious diseases
are still the main cause
今でも 世界中の人々の主要な死因で
00:15
of human suffering and death
around the world.
毎年 何百万もの人が
結核やマラリア、HIVで亡くなっています
00:18
Every year, millions of people die
of diseases such as T.B., malaria, HIV,
00:23
around the world
and even in the United States.
世界中で アメリカでもです
00:25
Every year, thousands of Americans
die of seasonal flu.
毎年 何千人ものアメリカ人が
季節性インフルエンザで亡くなります
もちろん 私たち人間はクリエイティブですよね?
00:29
Now of course, humans,
we are creative. Right?
00:31
We have come up with ways to protect
ourselves against these diseases.
こうした病気から身を守る方法を発見してきました
薬やワクチンです
00:34
We have drugs and vaccines.
00:36
And we're conscious --
we learn from our experiences
私たち人間は経験から学び
創造的な解決策を考える生き物です
00:39
and come up with creative solutions.
これは人間だけの習性だと思われてきましたが
00:41
We used to think we're alone in this,
but now we know we're not.
今はそうではないことがわかっています
人間だけが医師ではありません
00:44
We're not the only medical doctors.
00:46
Now we know that there's a lot of animals
out there that can do it too.
同じことができる動物が数多くいます
最も有名なのはおそらくチンパンジーで
00:49
Most famous, perhaps, chimpanzees.
私たちと大差なく
00:51
Not so much different from us,
腸の寄生虫退治に
植物を使うことができます
00:52
they can use plants
to treat their intestinal parasites.
でもここ数十年で 他にも同じことができる
生き物がいることが分かってきました
00:55
But the last few decades have shown us
that other animals can do it too:
ゾウ、ヤマアラシ、ヒツジ、ヤギなどです
00:59
elephants, porcupines,
sheep, goats, you name it.
そしてさらに面白いことに
最近の研究によると
01:02
And even more interesting than that
is that recent discoveries are telling us
昆虫など小さな脳を持つ動物も
薬草を用いているということです
01:06
that insects and other little animals with
smaller brains can use medication too.
ご存知のとおり 感染症の問題は
01:11
The problem with infectious diseases,
as we all know,
病原体が進化し続けるので
01:14
is that pathogens continue to evolve,
01:16
and a lot of the drugs
that we have developed
どんなに薬を開発しても
効かなくなってしまうことです
01:18
are losing their efficacy.
01:19
And therefore, there is this great need
to find new ways to discover drugs
ですから そうした病気に対する
薬を開発するために
新たな方法を見つける必要があります
01:24
that we can use against our diseases.
01:26
Now, I think that we
should look at these animals,
ですから 私はこうした動物たちに目を向け
01:28
and we can learn from them
how to treat our own diseases.
彼らから 私たちの病の治療法を
学べると思います
01:32
As a biologist, I have been studying
monarch butterflies for the last 10 years.
生物学者の私はオオカバマダラという蝶を
10年間研究してきました
この蝶の大移動は有名で
01:36
Now, monarchs are extremely famous
for their spectacular migrations
毎年アメリカ、カナダからメキシコまで
01:39
from the U.S. and Canada
down to Mexico every year,
何百万頭もの群れで移動します
01:43
where millions of them come together,
01:45
but it's not why I started studying them.
でも 私がこの蝶を研究し始めた理由は
この蝶が病気にかかるからです
01:47
I study monarchs because they get sick.
あなたや私と同じようにです
01:50
They get sick like you.
They get sick like me.
ですから この蝶の行動を研究すれば
01:52
And I think what they do
can tell us a lot about drugs
人間のための薬の開発に役立つと思います
01:55
that we can develop for humans.
この蝶に寄生するのは
01:57
Now, the parasites
that monarchs get infected with
“Ophryocystis elektroscirrha”
難しい名前です
01:59
are called ophryocystis elektroscirrha --
a mouthful.
この原生動物は何百万もの胞子を
02:03
What they do is they produce spores,
02:05
millions of spores
on the outside of the butterfly
蝶の体表に生み出します
02:07
that are shown as little specks
in between the scales of the butterfly.
蝶の大きさと比べれば
小さな点のような胞子ですが
蝶にとっては非常に有害です
02:11
And this is really detrimental
to the monarch.
これが蝶の寿命を縮め
02:13
It shortens their lifespan,
02:15
it reduces their ability to fly,
飛ぶ能力を減退させ
02:17
it can even kill them
before they're even adults.
羽化する前に死ぬこともあります
02:19
Very detrimental parasite.
とても有害な寄生虫なんです
私は研究のため 多くの時間を使って
温室で植物を育てています
02:21
As part of my job, I spend a lot of time
in the greenhouse growing plants,
その理由はこの蝶は食べ物の選り好みが
激しいからです
02:25
and the reason for this is that monarchs
are extremely picky eaters.
幼虫はトウワタしか食べません
02:29
They only eat milkweed as larvae.
02:31
Luckily, there are several
species of milkweed that they can use,
幸運にも食べられるトウワタは
何種類かありますが
02:34
and all these milkweeds
have cardenolides in them.
この植物にはカルデノリドが含まれています
カルデノリドは有害な化学物質です
02:36
These are chemicals that are toxic.
02:38
They're toxic to most animals,
but not to monarchs.
多くの動物にとって有害ですが
蝶は例外です
02:41
In fact, monarchs
can take up the chemicals,
実際 蝶はこの化学物質を
体内に取り込むことで
02:43
put it in their own bodies,
and it makes them toxic
鳥のような捕食者を避けるため
02:45
against their predators, such as birds.
自らの身体を有害にするのです
02:48
And what they do, then,
is advertise this toxicity
そして彼らはこの毒性を
02:50
through their beautiful
warning colorations
オレンジ、黒、白という
美しい色合いによって警告しています
02:52
with this orange, black and white.
私は研究の一環として
温室で この植物を育てました
02:54
So what I did during my job
is grow plants in the greenhouse,
02:58
different ones, different milkweeds.
何種類ものトウワタです
03:00
Some were toxic, including
the tropical milkweed,
いくつかは有害で
非常に高濃度の
カルデノリドを含む
熱帯性のものや
03:02
with very high concentrations
of these cardenolides.
無害なものを育てました
03:06
And some were not toxic.
そしてそれらを蝶に与えました
03:07
And then I fed them to monarchs.
中には病にかかっていない
元気な蝶もいましたが
03:09
Some of the monarchs were healthy.
They had no disease.
病気の蝶もいました
03:12
But some of the monarchs were sick,
そして発見したのは
あるトウワタには薬効性があり
03:14
and what I found is that
some of these milkweeds are medicinal,
蝶に食べさせると
病状を和らげるため
03:17
meaning they reduce the disease symptoms
in the monarch butterflies,
感染した蝶が長生きできるという
03:20
meaning these monarchs can live longer
when they are infected
効果があるということでした
03:23
when feeding on these medicinal plants.
これを発見した時
ある考えが浮かびました
03:25
And when I found this, I had this idea,
多くの人にばかげていると言われましたが
03:28
and a lot of people said
it was a crazy idea,
蝶がこれを使ったらどうなるだろう?
03:30
but I thought,
what if monarchs can use this?
蝶が自らの薬として
これらの植物を使ったら?
03:32
What if they can use these plants
as their own form of medicine?
03:35
What if they can act as medical doctors?
蝶が医者のように植物を使ったら?
03:38
So my team and I
started doing experiments.
そこで私たちのチームは実験を始めました
03:40
In the first types of experiments,
最初の実験では
03:42
we had caterpillars,
and gave them a choice:
幼虫に選択肢を与えました
薬効性があるトウワタと
そうでないトウワタで
03:44
medicinal milkweed versus
non-medicinal milkweed.
03:47
And then we measured how much they ate
of each species over their lifetime.
幼虫が一生の間に食べる
植物の量を測定しました
03:51
And the result, as so often
in science, was boring:
結果は科学によくありがちな
退屈なもので
03:54
Fifty percent of their food was medicinal.
Fifty percent was not.
50%が薬草
50%が薬効性のない植物でした
03:58
These caterpillars didn't do
anything for their own welfare.
幼虫は健康のために
何もしていなかったのです
04:02
So then we moved on to adult butterflies,
次に私たちは成虫になった
蝶に目を向けました
04:04
and we started asking the question
私たちが着目したのは
04:06
whether it's the mothers
that can medicate their offspring.
母である蝶が子どもに
薬草を与えるかということです
母蝶が未来の子どもたちが
病にかかりにくくするよう
04:09
Can the mothers lay their eggs
on medicinal milkweed
04:12
that will make their
future offspring less sick?
薬草であるトウワタに
卵を産み付けるか?と
この実験を これまで数年間
続けてきましたが
04:15
We have done these experiments now
over several years,
結果はいつも同じです
04:18
and always get the same results.
私たちは蝶を大きなカゴに入れ
04:20
What we do is we put
a monarch in a big cage,
薬草と そうではない植物を
両端に置いて
04:22
a medicinal plant on one side,
a non-medicinal plant on the other side,
それぞれの植物に産み付けられた
卵の数を数えます
04:25
and then we measure the number of eggs
that the monarchs lay on each plant.
04:30
And what we find when we do that
is always the same.
すると結果はいつも同じです
蝶は薬草であるトウワタを
強く好むことがわかりました
04:33
What we find is that the monarchs
strongly prefer the medicinal milkweed.
つまり メスの蝶は
04:36
In other words,
what these females are doing
68%の確率で薬効性のある
トウワタの上に産卵しています
04:39
is they're laying 68 percent
of their eggs in the medicinal milkweed.
面白いことに 彼らは産卵する時
04:42
Intriguingly, what they do
is they actually transmit the parasites
実際に寄生虫も伝染させます
04:46
when they're laying the eggs.
04:48
They cannot prevent this.
これは防ぎようがありません
04:49
They can also not medicate themselves.
彼らは自分で治療もできません
04:51
But what these experiments tell us
しかしながら これらの実験から
母蝶が未来の子どもを
病から遠ざけることができる
04:53
is that these monarchs, these mothers,
can lay their eggs on medicinal milkweed
薬効性のあるトウワタの上に
産卵できることがわかりました
04:58
that will make their
future offspring less sick.
05:03
Now, this is a really
important discovery, I think,
これは非常に重要な発見だと思います
05:05
not just because it tells us
something cool about nature,
単なる自然の素晴らしさを
教えてくれるだけでなく
私たちの薬を見つけるためのヒントが
あるかもしれないからです
05:08
but also because it may tell us something
more about how we should find drugs.
これらの動物はとても小さく
05:12
Now, these are animals that are very small
05:14
and we tend to think of them
as very simple.
人間はとても単純だと思いがちです
05:16
They have tiny little brains,
彼らの脳はとてもちっぽけです
05:17
yet they can do this
very sophisticated medication.
でも彼らには非常に洗練された
薬物療法を利用しています
今日でさえ 私たちが使う薬の多くは
05:20
Now, we know that even today,
most of our drugs
植物などを含む自然由来です
05:23
derive from natural products,
including plants,
古来の文化では
05:26
and in indigenous cultures,
伝統的な治療者は 新たな薬を発見するために
動物を調べます
05:27
traditional healers often look
at animals to find new drugs.
ゾウは胃もたれを治す方法を
05:30
In this way, elephants have told us
how to treat stomach upset,
ヤマアラシは出血を伴う下痢を治す方法を
教えてくれているのです
05:34
and porcupines have told people
how to treat bloody diarrhea.
けれども重要なことは
05:37
What I think is important,
though, is to move beyond
05:39
these large-brained mammals
and give these guys more credit,
このような大きな脳を持つ
ほ乳類を越えて ちっぽけな脳を持ち
05:43
these simple animals, these insects
that we tend to think of
単純だと考えがちな
小さな動物や昆虫を
05:46
as very, very simple
with tiny little brains.
もっと認めることです
こうした小さな生き物たちも
薬物療法を使うという発見は
05:49
The discovery that these animals
can also use medication
全く新たな道を切り開くものといえます
05:53
opens up completely new avenues,
私が思うに いつの日か
蝶によって初めて見つけられた薬で
05:56
and I think that maybe one day,
we will be treating human diseases
人間の病気を治療する日が来るでしょう
06:01
with drugs that were first
discovered by butterflies,
これはこの先も追求すべき
素晴らしい好機だと思います
06:04
and I think that is an amazing opportunity
worth pursuing.
ありがとうございました
06:08
Thank you so much.
(拍手)
06:10
(Applause)
Translated by Tomomi Anzai
Reviewed by Hiroko Kawano

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About the Speaker:

Jaap de Roode - Biologist
Jaap de Roode studies the ecology and evolution of parasites, focusing on those that attack the monarch butterfly.

Why you should listen

At his lab at Emory University, Jaap de Roode and his team study parasites and their hosts. Some of the questions that intrigue them: If a parasite depends on its host's survival for its own well-being, why do so many of them cause harm? In what ways are hosts able to self-medicate in order to make themselves less desirable to parasites? And are the abilities to harm hosts — and the ability of hosts to self-medicate — favored by natural selection?

The De Roode Lab focuses on the monarch butterfly and its parasites. The team has made a fascinating discovery: that female butterflies infected by a parasite choose to lay their eggs on a specific variety of milkweed that helps their offspring avoid getting sick. De Roode hopes that this insight could lead to new approaches in medications for human beings in the future.

More profile about the speaker
Jaap de Roode | Speaker | TED.com