你好毒

Snake Venom

夺宝奇兵,航班蛇患,甚至哈利波特与密室,这些电影都依赖于观众对于蛇的恐惧来制造悬疑和紧张感。大约有三分之一的人至少有点怕蛇。人们对蛇的恐惧部分来自于爬行巨蛇出其不意的行动方式,当然还因为人们知道有的蛇会咬死人,每年大概有四万九千多人被蛇咬死。

但蛇毒并非生来平等。有些蛇毒只能毒死几只老鼠。而另一些些则出了名的恶毒,比如澳大利亚有一种内陆太攀蛇,它的毒液足以杀死五十个成年人。爱尔兰国立高威大学的动物学系的讲师凯文西里说。

他想知道为什么不同蛇毒的毒性差距这么大,于是他和团队研究了一百零二种毒蛇。他们考查了毒液量,蛇的食物,还有栖息环境,结果发现,总体而言蛇越大,毒越越多。但毒液的多少基本上取决于毒蛇每秒钟消耗多少能量,并不是你可能以为的蛇的猎物大小。这项研究发表在生态通信期刊上。

研究人员还发现,在三维环境下,比如生活树林里和水里的蛇,毒液要比在二维环境中,比如在地面上生活的蛇毒液量少。

我们猜想,这还是和遇见猎物的概率有关。如果你生活在三维环境,这种三维环境的物理特征,就意味着你可以遇到更多的猎物,无需大量毒液储备。如果猎物不常见,错过了一个猎物,下餐就得饿肚子。所以生活在二维环境,一旦有机会捕食,毒蛇就要靠毒液重拳出击。当然,毒蛇只占所有的蛇的四分之一。记住这一点,可能会让你比夺宝奇兵中的印第安纳琼斯勇敢一点。不过,在行驶的卡车下面爬行,还是需要勇气。

原文

Movies like Raiders of the Lost Ark, Snakes on a Plane and even Harry Potter and the Chamber of Secrets have all relied on the fear of snakes to build suspense and anxiety. About a third of all people are at least a bit phobic about snakes. Some of the distress when it comes to the slithering serpents comes from their unpredictable movement patterns. But the fear also stems from knowing that, well, snake bites do kill a lot of people—perhaps as many as 94,000 people annually.

But not all snake venom is created equal. Some snakes have venom only strong enough to kill a couple of mice. On the other hand, there’s “the inland taipan in Australia, which is incredibly venomous. It has enough potent venom to kill about 50 adults. Humans.” Kevin Healy, a lecturer in zoology at the National University of Ireland, Galway.

He wanted to know why snake venom toxicity varied so much, so he and his team looked at 102 different venomous snakes species. They examined how much venom the snakes had as well as what they ate and what kind of habitat they lived in. The key finding: “Bigger snakes have more venom, in general. But the amount of the increase of that venom increases basically according to how much energy you burn per second, not how big your prey is, as you'd expect.” The study was in the journal Ecology Letters.

The researchers also found snakes that inhabited three-dimensional environments that include things like trees and water had less venom than snakes that live two-dimensionally—that is, on the ground.

“Our guess is that that comes back to encounter rate. So if you live in a 3D environment, just the pure physics of living in a 3D environment means you will bump into more things. And so what that means is you might not need this really large reservoir of venom to kind of ensure that if you miss a prey item, that you have something for the next time because you're not going to get to encounter individuals that often.”

Whereas the 2D-dwelling snakes need to make sure that when they get a chance for a meal, their venom will pack a punch. Of course, only about a quarter of all snake species have venom at all. Keeping that in mind may make it possible to be braver than Indiana Jones—when it comes to snakes, at least. You should still be very scared to crawl under a moving truck.

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