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来源How King Cobra Maintains Its Reign - NYTimescom
译者epicwu I can remember the first time I saw one, at the St. Louis Zoo, and the feeling that certain death was just on the other side of the glass. I could not get over the snake’s size — this one was about 12 feet long. I was used to looking at giant snakes in zoos (I always made a beeline for the reptile house), but pythons did not seem so scary to me because they rarely moved. This sleek, agile and very alert snake was a king cobra, the largest venomous snake in the world and an icon to all snake enthusiasts, including this writer. 我还记得在圣路易斯动物园第一次看到它的情形，玻璃的另一边充斥着死亡的气息。巨大的体型让我难以克服（恐惧）——这一条有12英尺长。我以前也在动物园里看过巨蟒（我常常直奔爬行动物馆），但蟒蛇们并不能带来这样的恐惧，因为他们很少动。而眼前这条圆滑、机敏而又警觉的爬行动物叫做眼镜王蛇——世界上最大的毒蛇。它也是包括作者在内的蛇类发烧友的偶像。 The king cobra’s venom is not, ounce for ounce (or milligram for milligram, as the professionals would measure it), the most potent. Among land snakes, that honor appears to belong to the inland taipan of Australia. But what the king cobra lacks in potency, it makes up for in volume. Its half-inch fangs deliver a huge dose, up to seven milliliters of venom, or about one-quarter of a whiskey shot glass. The lethality of venom depends on a combination of its potency, the volume delivered and the size of the victim. A king cobra bite can kill a human in 15 minutes and a full-grown elephant in a few hours.
眼镜王蛇的毒液，如果按每盎司（或者按毫克，这取决于专家们如何测量他）算并不是最毒的。在陆生蛇类中，这一荣誉属于澳大利亚的内陆太攀蛇。“质”不行，用“量”补。眼镜王蛇半英寸长的毒牙能分泌大量，最多达到7毫升毒液，这能装满威士忌小酒杯的四分之一。毒液的杀伤性取决于毒液量和受害者的体型。被眼镜王蛇咬一口，人类将会在15分钟内死亡，而成年大象也只能坚持几个小时。 What makes these cobras kings is not just their size, or their deadliness — after all, they don’t eat humans or elephants — it is that they eat other snakes. Even deadly snakes like kraits or other cobras are prey. These snakes bite when attacked, of course, which raises the question: How does the king cobra maintain such an apparently high-risk lifestyle? 然而眼镜王蛇，之所以叫“王蛇”，并不是因为他的体型和致命性——实际上，他们并不吃人或者大象——而是因为他们吃别的蛇。就算是如金环蛇一样致命的毒蛇也是他们的猎物。这些毒蛇被攻击时自然会反咬一口，那么这就引出了一个问题：眼镜王蛇是如何维持这样一种明显高风险的生活方式的？ Krait and cobra venoms, including that of the king cobra, act very quickly by crippling the nervous system. Among the arsenal of weapons in the snakes’ venom is one especially potent neurotoxin that works by binding to receptors on muscle cells. The toxin blocks the ability of acetylcholine, one of the body’s chemical neurotransmitters, to control muscle contraction. The blocking of these receptors causes paralysis, respiratory failure and death. 金环蛇和眼镜蛇（包括眼镜王蛇）的毒液，通过削弱神经系统快速生效。在毒液的“军火库”中，有一种特殊的神经毒素，它能致盲肌肉细胞中的受体。这些毒素能阻塞乙酰胆碱（身体内的一种化学神经递质，能够控制肌肉反馈）的活动。这些受体的阻塞将会引起麻痹、呼吸衰竭和死亡。 But the king cobra is not fazed by bites from its victims. Biochemists have carefully mapped exactly how neurotoxins block the acetylcholine receptor of many species, and they have discovered that the toxins do not bind to the cobra’s receptor. Mutations have altered the snake’s receptor in such a way that, because the toxin cannot bind to the receptor, the acetylcholine function is undisturbed. The king cobra can subdue its dinner without suffering from any venomous counterattack. 但是眼镜王蛇被咬了之后却没什么事。生物化学家已经仔细而准确的绘制出了许多物种被神经毒素阻塞乙酰胆碱受体的过程。但是他们发现毒素并不会致盲这种眼镜蛇的受体。基因突变改变了这种蛇的受体，使得毒素无法致盲受体，乙酰胆碱的功能亦未受影响。因此眼镜王蛇可以从容征服他们的“晚餐”而不必遭受毒液的反击。 This large snake, resistant to the very potent venoms of its prey, would appear then to be impervious. But we all know the story of the mongoose, if not from wildlife programs then from Rudyard Kipling’s tale “Rikki-Tikki-Tavi.” How does the mongoose defeat the king cobra? 这种大型蛇类，即便中了受害者的致命毒液，也能毫发无伤。但我们都听说过猫鼬（捕杀眼镜王蛇）的故事，无论是从野生动物节目上还是Rudyard Kipling的故事“Rikki-Tikki-Tavi”里。那么，这些猫鼬是如何击败眼镜王蛇的呢？ The mongoose’s quick reflexes help it dodge the cobra’s defensive bite, and its powerful jaws can dispatch a snake in one blow. But there are also genetic grounds for the mongoose’s courage. Sometimes an attacking mongoose is bitten, but it has another line of defense against the venom — its acetylcholine receptor has also evolved so that the cobra neurotoxin cannot bind to it. A set of changes in the mongoose’s receptor makes it resemble the cobra’s own resistant receptor. 猫鼬快速的反应可以帮助他躲避眼镜蛇的防御性攻击，它有力的下颚能够一下子杀死一条蛇。除此之外，猫鼬的勇气，还有遗传学的根据。有时猫鼬也会被咬到，但它还有除了反应之外的第二种防御毒液的方式——它的乙酰胆碱受体同样进化到了不怕眼镜蛇神经毒素的地步。猫鼬受体的一系列变化使得它们类似于眼镜蛇自己的抗毒液性受体。 The mongoose’s evolutionary adaptation is not unique. Other small, humble creatures have evolved ways to endure what for most animals would be lethal snakebites, and some of these resistant animals turn the tables to conquer and consume their venomous foes. 猫鼬的进化与适应并不是独一无二的。其他微小、低等的生物也进化出了抗（对大多数动物来说是致命的）蛇咬的能力，他们中的一部分抗性动物成功扭转了战局，征服并消耗着他们有毒的敌人。 Sea snakes generally possess very toxic venoms. While the snakes rarely bite humans in the water, fishermen are struck occasionally when sifting through their trawls and have died from the bites of some species. The potent venom is not meant for large animals like ourselves, of course. Sea snakes prey on small marine animals, and the powerful toxins in the venom quickly immobilize the prey before it can swim off. Eels are some of the favorite foods of the banded sea krait. Some eels, however, have been observed to be remarkably resistant to the sea krait’s venom. 海蛇一般都有剧毒。虽然它们很少在水里咬人，渔民还是偶尔会在撒网的时候中招，如果运气不好碰上其中几种毒性强的，还会因此丧命。这种强效毒液显然并不是冲着像我们这样的大型动物来的。海蛇经常捕捉小型水生动物，他们毒液中强有力的毒素会迅速使猎物在游走前丧失移动能力。鳗鱼是巨环海蛇最喜爱的食物。然而现在已经发现，有一部分鳗鱼已经体现出了对巨环海蛇毒液的明显抗性。 Harold Heatwole and Judy Powell of North Carolina State University showed that undulated moray eels and liver-colored moray eels found in the waters around New Guinea can tolerate several hundred times the venom dose that kills spotted moray eels from the Bahamas. 北卡罗莱纳州立大学的Harold Heatwole和Judy Powell证明，在新几内亚发现的波状鳝鳗和猪肝色海鳗可以忍受的毒液量，是杀死巴拿马斑纹鳝鳗所需毒液量的几百倍。 The biologists’ explanation for the great disparity in the sensitivity of eel species is that sea snakes are not found in the Atlantic Ocean, so there has been no selective pressure on eels there, whereas in the Pacific, where sea snakes are abundant, selection has been so intense that some eel species have evolved resistance. 生物学家们对于海鳗抗性不同的解释是：大西洋里没有发现过海蛇，因此这里的海鳗没有自然选择的压力，但在太平洋，海蛇分布丰富，巨大的自然选择压力使得一部分海鳗品种进化出了抗性。 A similar situation has evolved among California ground squirrels with respect to the venom of northern Pacific rattlesnakes. This species and most other rattlesnakes kill their prey with a battery of toxins that is different from those of sea snakes and cobras. Rattlesnake venom toxins work by breaking down tissues and causing internal bleeding. 相似的演变同样发生在加利福尼亚本地松树和北太平洋响尾蛇之间。这种响尾蛇和大多数其他的响尾蛇一样，依靠的是一组有别于海蛇和眼镜蛇的毒素。响尾蛇的毒素是通过破坏组织结构引起内出血来生效的。 A good-size rattlesnake can deliver a hefty dose of venom that is sufficient to kill a human if the bite is left untreated. But ground squirrels in some parts of California, despite being one hundredth the size of humans, exhibit fairly mild effects from the venom. This resistance is not the result of altered receptors, but comes from the ability of proteins in their blood serum to neutralize the effects of venom. 一条大号的响尾蛇能产生大量毒素，如果不做处理的话，足以杀死一个人。但加利福尼亚部分地区的当地松鼠，并没有变大一百倍达到人的大小，毒素对其却只有轻微的副作用。这种抗性并不是受体变化的结果，而是松鼠血清里蛋白质的作用，它们能抵消毒液的影响。 But squirrels of the same species from Alaska, where the rattlesnakes are absent, exhibit much greater sensitivity to the venom, and their serum is much less effective at neutralizing the venom. These observations suggest that in some areas where the rattlesnakes are abundant, local squirrel populations have evolved a degree of resistance. 而在没有响尾蛇分布的阿拉斯加，同一品种的松鼠对毒液的反应要剧烈的多，他们的血清中和毒素的能力也大大弱于加利福尼亚的。这些观察说明，在响尾蛇分布广泛的地区，当地松鼠会进化出一定程度的抗性。 One family of completely harmless snakes, the kingsnake, has also evolved serum that neutralizes rattlesnake venom and uses that ability to greater advantage than ground squirrels do. Kingsnakes are a group of beautiful constrictors found in many parts of the United States. As their name indicates, kingsnakes eat other snakes — they do not hesitate to attack, kill and consume rattlesnakes. 完全无毒蛇大家庭中的一种，王蛇，也进化出了能中和响尾蛇毒液的血清，并且靠着这一能力获得了比松鼠们更大的好处。王蛇是一群在美国很多地方都有发现的美丽蟒蛇。蛇如其名，王蛇会吃其他种类的蛇——在攻击、杀死、消化响尾蛇时，他们从不犹豫。 These stories of evolution are a bit like Shakespearean dramas, where the one best able to carry out or to thwart poisonous schemes winds up becoming king. Snakes in general, let alone cobras, will never be much loved by humans, but these animals are so extraordinary, this enthusiast cannot resist one sentimental thought: Long live the kings. 这些进化的故事就像莎士比亚的戏剧一样，最擅长实现或者挫败阴谋的人最后会变成国王。总而言之，蛇，尤其是眼镜蛇，永远不会得到人类太多的喜爱。但这些动物是如此与众不同，以至于狂热者们无法抵抗一个感伤的想法：愿国王万岁！ 相关文章： |
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