【TED】Why are cockroaches so hard to kill

In the Egyptian Book of the Dead, there’s a banishment spell that declares, “Be far from me, O vile cockroach.” More than 3,000 years later, we’re still trying to oust these insects. But from poison traps to hastily brandished slippers, cockroaches seem to weather just about everything we throw at them. So what makes cockroaches so hard to kill?

在埃及的死亡之书里 写着一条驱逐咒语： “可恶的蟑螂啊，请远离我。” 三千多年以后， 我们还在尝试消灭这群虫子。 从毒药陷阱到仓卒挥舞的拖鞋， 蟑螂似乎对我们所有的招数 都能迎刃而解。 所以到底为什么蟑螂 这么难杀死呢？

There are nearly 5,000 cockroach species. 99% of them live in a range of habitats where they play important ecological roles by recycling dead or decaying organic matter and nourishing other animals. But a couple dozen species adapted to live in close association with humans. German and American cockroaches are among the most common. And they owe their resilience to a combination of physical and chemical adaptations.

世界上有近 5,000 种蟑螂。 99 %的蟑螂在广泛的栖息地中 扮演了重要的生态角色， 它们回收利用死物， 或者腐烂有机物， 还有滋养其他动物。 但几个种类的蟑螂 适应了与人类密切生活， 其中最普遍的是 德国和美国的蟑螂。 它们的抵御能力源于 物理和化学适应的结合。

When it comes to old-fashioned removal methods, they're troublingly tenacious. An American cockroach’s sensory hairs or structures pick up subtle air currents and rapidly send signals to its central nervous system. The roach can then turn and sprint away within a few milliseconds. And it’s among the fastest invertebrates ever recorded, reaching speeds of up to 50 body lengths per second. This would be the human equivalent of running more than 300 kilometers per hour. And finding a hiding place is no problem. With its flattened, flexible body, an American cockroach can squeeze into spaces less than a quarter of its height. Even if we do land a hit, it can withstand compressive forces of up to 900 times its own weight by distributing the impact along its body.

说到老式的清除方法， 它们是令人讨厌的麻烦。 一只美国蟑螂的感官毛发或结构 能捕捉到细微的气流， 然后迅速地向中央神经系统 传递信号， 蟑螂可以在几毫秒内 转身冲刺离开。 蟑螂有史以来速度 最快的无脊椎动物之一， 它可以达成每秒高达 50 个体长的速度。 这大概是人类跑步达到高于 300 千米每小时的速度。 对蟑螂来说， 找到一个躲避所毫不费吹灰之力。 由于其扁平和灵活的身体， 美国蟑螂可以挤进不到其身高 四分之一的空间里。 即使我们打中了蟑螂， 它可以通过分布冲击力到身体部分 来承受高达其自身重量 900 倍的挤压力。

And the cockroach’s toughness doesn’t end there. Cockroaches can eat a variety of organic matter, including hair, dead skin, adhesives, and paper. This is made possible by an expansive set of digestive enzymes. Cockroaches are able to thrive even in nutrient-poor environments. Roaches often eat decaying foods that are low in nitrogen— an essential component of DNA and proteins. But they survive by storing nitrogen-containing wastes in their bodies and having a resident group of bacteria recycle the nitrogen into useful molecules for them.

蟑螂的韧性不只只有这些， 蟑螂可以食用不同的有机物， 包括头发、死皮、黏合剂和纸张。 这是因为蟑螂丰富的消化酶。 蟑螂可以在营养贫乏的环境下 繁衍生息。 蟑螂经常食用低氮的腐化食物， 一种至关重要的DNA 和蛋白质的组成部分。 蟑螂在它们体内储存 含氮的废物来存活， 并且有一群常住细菌 将氮气回收利用成 对它们有用的分子。

Meanwhile, German cockroaches will eat their own poop, vomit, and dead or dying colony members without hesitation. An American cockroach will frolic in sewers, consuming excrement and toting microbes like Staphylococcus aureus and E.coli. But they’ll rarely suffer any consequences. This is because they’re equipped with genes that provide immunity against numerous pathogens. These genes are often duplicated many times over. So when infected, the cockroach’s immune system efficiently unleashes many antimicrobial molecules.

与此同时，德国蟑螂可以吃它们 自己的排泄物和呕吐物， 并且会毫不犹豫地食用 死去的或濒临死亡的群体成员。 一只美国蟑螂会在下水道里嬉戏， 食用排泄物和微生物， 诸如金黄葡萄球菌 （Staphylococcus aureus ） 和大肠杆菌（E.coli）。 蟑螂鲜少承受任何食用 这些东西的后果。 这是因为它们有着 提供免疫数多病原体的基因。 这些基因经常不停地复制， 当蟑螂被感染时， 它的免疫系统有效的释放出 许多抗菌分子。

Cockroaches also have a slew of defenses against pesticides. When a non-resistant roach walks on a surface that’s been sprayed with a pyrethroid insecticide, for example, the results will likely be fatal. Once absorbed, the chemical binds to sodium channel proteins, which help propagate nerve impulses. The pyrethroid keeps the sodium channels open, so the nerves fire repeatedly. And soon, the cockroach dies. But if a resistant roach is exposed to pyrethroids, it’ll be just fine. Genetic mutations have given them sodium channels that the pyrethroids can’t bind to. The cockroach also produces more detoxification enzymes, which render the pesticide harmless, and the cockroach simply excretes it as a waste. Because German cockroaches reproduce especially quickly, populations may evolve resistance to a new pesticide within months. So far, they're already resistant to 43 different chemicals.

蟑螂对杀虫剂 也有一连串的防御措施。 举个例子， 当一只没有任何抵抗力的蟑螂 走在被喷洒过 拟除虫菊酯杀虫剂的地面， 这极大可能是致命的。 一旦吸收， 这些化学品与钠通道蛋白结合， 这有助于传播神经冲动。 拟除虫菊酯 使钠离子通道保持开放， 导致神经不停地发射。 很快，蟑螂就会死去。 但对于一只有对抗性的蟑螂来说， 基因变异给了它们拟除虫菊酯 不能束缚的钠离子通道。 蟑螂还能产生更多的解毒酶， 从而使杀虫剂无害， 蟑螂只是把它作为废物排出体外。 由于德国蟑螂繁殖的速度特别快， 它们的种群可能在一个月内 进化出抵御新的杀虫剂的抵抗力。 目前来说，德国蟑螂已经有对 43 不同化物的抵抗力。

But contrary to popular belief, cockroaches would probably not survive a nuclear apocalypse. Compared with other insects, cockroaches are only mildly tolerant to radiation. They would die near the sites of nuclear explosions and would still be severely compromised miles away. Moreover, disasters that threaten humanity also jeopardize the habitats and buffets we provide roaches. Perhaps the only way to beat them is through our mutual destruction. Or maybe cockroaches would find even more surprising ways to thrive long after we’re gone.

但与大众的看法相反， 相比于其它昆虫， 蟑螂大概不会在核灾难中 存活下来。 由于蟑螂对辐射 只有轻微的免疫性， 它们会在核爆炸地区的附近死亡， 并在数英里之外 仍然受到重大影响。 此外，威胁到人类的灾难 同样会威胁到人们提供给 蟑螂的生长地和自助餐。 也许唯一个完全消灭蟑螂的方法是 人类和蟑螂的共同毁灭。 又或许，蟑螂在人类消失后， 还能可以找到更加令人惊讶的方法 继续繁衍生息。