when Charles Darwin was still a student at Cambridge,

當查爾斯．達爾文還是劍橋的學生時

the budding naturalist tore some old bark off a tree

這位初嶄露頭角的博物學者從一棵樹上剝下了一些老樹皮

and found two rare beetles underneath.

然後在底下發現了兩隻罕見的甲蟲

He'd just taken one beetle in each hand when he spotted a third beetle.

當他兩手各拿了一隻甲蟲時，他發現了第三隻

Stashing one of the insects in his mouth for safekeeping,

他把其中一隻昆蟲塞到嘴裡以防牠逃走

he reached for the new specimen –

伸手想抓那隻新樣本時 --

when a sudden spray of hot, bitter fluid scalded his tongue.

一陣突如其來的炙熱苦澀液體燙傷了他的舌頭

Darwin's assailant was the bombardier beetle.

攻擊達爾文的是投彈甲蟲

It's one of thousands of animal species,

那是千種動物品種的其中一員

like frogs,

其他還有青蛙、

jellyfish,

水母、

salamanders,

火蜥蜴、

and snakes,

和蛇

that use toxic chemicals to defend themselves –

這些群體會利用有毒化學物質來防衛自己 --

in this case, by spewing poisonous liquid from glands in its abdomen.

在這個例子中，就是藉由噴射腹部分泌腺的有毒液體

But why doesn't this caustic substance, ejected at 100 degrees Celsius,

但為什麼這種腐蝕性的物質，更不用說它噴射時溫度達攝氏一百度

hurt the beetle itself?

不會傷及甲蟲本身？

In fact, how do any toxic animals survive their own secretions?

事實上，任何有毒動物是如何活過他們自己的分泌物？

The answer is that they use one of two basic strategies:

答案是牠們在兩個基本的策略之間擇一使用：

securely storing these compounds

安全地儲存這些混合物

or evolving resistance to them.

或是演化出對它們的抵抗力

Bombardier beetles use the first approach.

投彈甲蟲使用第一套策略

They store ingredients for their poison in two separate chambers.

牠們將毒藥的成分儲存在兩個獨立的腔室

When they're threatened, the valve between the chambers opens

當牠們受到威脅，兩個腔室之間的閘門就會打開

and the substances combine in a violent chemical reaction

物質混合成一種激烈的化學反應

that sends a corrosive spray shooting out of the glands,

最後從腺體噴射出腐蝕性噴霧

passing through a hardened chamber that protects the beetle's internal tissues.

途中經過硬化的、能夠保護甲蟲體內組織的腔室

Similarly, jellyfish package their venom safely

同樣地，水母將牠們的毒液安全地包裹在

in harpoon-like structures called nematocysts.

叫做刺絲胞的魚叉狀構造內

And venomous snakes store their flesh-eating, blood-clotting compounds

而有毒的蛇則是將牠們腐肉、凝血的混合物

in specialized compartments that only have one exit:

儲存在只有一個出口的特殊小隔間內：

through the fangs and into their prey or predator.

只能經由獠牙進入牠們的獵物或是狩獵者

Snakes also employ the second strategy: built-in biochemical resistance.

蛇同樣採用了第二套策略：內建的生物化學抵抗力

Rattlesnakes and other types of vipers manufacture special proteins

響尾蛇和其他種類的毒蛇會製造一種特殊的蛋白質

that bind and inactivate venom components in the blood.

能夠在血液中使毒液成分凝結、失效

Meanwhile, poison dart frogs have also evolved resistance to their own toxins,

同時，毒鏢蛙也演化出對牠們自己毒素的抗體

but through a different mechanism.

但是透過不同的機制

These tiny animals defend themselves using hundreds of bitter-tasting compounds

這些小小的動物運用稱為生物鹼的

called alkaloids

百樣種苦澀混合物

that they accumulate from consuming small arthropods like mites and ants.

這些是從吃小小的節肢動物比如蟎蟲和螞蟻攝取而來

One of their most potent alkaloids is the chemical epibatidine,

牠們其中最有效的一種生物鹼是化學巴蒂啶

which binds to the same receptors in the brain as nicotine

與尼古丁作用於腦部中相同的受器

but is at least ten times stronger.

但卻至少強了十倍

An amount barely heavier than a grain of sugar would kill you.

只比些微糖粒多一點點的分量就能置你於死地

So what prevents poison frogs from poisoning themselves?

所以是什麼預防了毒蛙毒死自己？

Think of the molecular target of a neurotoxic alkaloid as a lock,

試著把神經中毒生物鹼的分子目標視為一個鎖

and the alkaloid itself as the key.

生物鹼本身則是鑰匙

When the toxic key slides into the lock,

當毒鑰匙滑進鎖頭

it sets off a cascade of chemical and electrical signals

它會促使一波化學電子訊號

that can cause paralysis,

會造成麻痺、

unconsciousness,

喪失意識、

and eventually death.

最終死亡

But if you change the shape of the lock, the key can't fit.

但如果你改變了鎖頭的形狀，鑰匙就會對不上

For poison dart frogs and many other animals with neurotoxic defenses,

對於毒箭蛙和許多其他有神經中毒防衛機制的動物

a few genetic changes alter the structure of the alkaloid-binding site

些微的基因改變會更改綁定生物鹼的區域構造

just enough to keep the neurotoxin from exerting its adverse effects.

正好防止了神經毒素造成反效果

Poisonous and venomous animals

有毒的和能散發毒素的動物

aren't the only ones that can develop this resistance:

並不是唯一可以發展出抵抗力的一方：

their predators and prey can, too.

他們的狩獵者或是獵物也可以

The garter snake, which dines on neurotoxic salamanders,

攝取帶有神經毒素的火蜥蜴為生的束帶蛇

has evolved resistance to salamander toxins

透過一些與火蜥蜴本身相同的基因改變

through some of the same genetic changes as the salamanders themselves.

已經演化出對火蜥蜴毒素的抵抗力

That means that only the most toxic salamanders can avoid being eaten—

那就代表，只有最毒的火蜥蜴才不會被吃掉 --

and only the most resistant snakes will survive the meal.

而且只有抵抗力最強的蛇能活過這餐

The result is that the genes providing the highest resistance and toxicity

結果是提供最高抵抗力和毒素的基因

will be passed on in greatest quantities to the next generations.

會以最大的數量傳承給下一代

As toxicity ramps up, resistance does too,

隨著毒素提升，抵抗力也是

in an evolutionary arms race that plays out over millions of years.

在這場演化軍備競賽中上演了百萬年

This pattern appears over and over again.

這個過程一再重複

Grasshopper mice resist painful venom from scorpion prey

沙居食蝗鼠藉由改變牠們神經系統中的基因

through genetic changes in their nervous systems.

抵抗來自蝎子獵物帶來疼痛的毒液

Horned lizards readily consume harvester ants,

角蜥迅速地吞食收割蟻

resisting their envenomed sting with specialized blood plasma.

抵抗牠們含有特殊血漿的有毒針刺

And sea slugs eat jellyfish nematocysts,

而海蛞蝓攝食水母刺絲胞

prevent their activation with compounds in their mucus,

藉由牠們黏液中的混合物防止毒素激活

and repurpose them for their own defenses.

然後把它們重新利用為自己的防衛利器

The bombardier beetle is no exception:

龐巴迪甲蟲也絕非例外：

the toads that swallow them

吞下牠們的蟾蜍

can tolerate the caustic spray that Darwin found so distasteful.

能夠忍受那種達爾文覺得非常討厭的腐蝕性噴霧

Most of the beetles are spit up hours later,

多數甲蟲會在幾小時後被吐出來

amazingly alive and well.

驚奇地還活著而且無恙

But how do the toads survive the experience?

但是蟾蜍又是如何活過這個經歷的？

That is still a mystery.

這還是個謎團