来源：沪江听写酷 2011-12-05 12:08
If you liked the colorful animals we just saw, you're going to love these next animals - frogs. You might not normally think of frogs as being colorful, but these frogs definitely are. They are the dart-poison frogs of Central and South America. Look at their striking colors - often yellow with black stripes or deep blue with black spots. Beyond being nice to look at, these markings have a purpose. They warn predators that these frogs are poisonous. When threatened, these frogs secrete a substance through their skin that would easily kill whatever animal might try to eat them. Their bright colors communicate this, and so most animals tend not to hunt them. Now, speaking of hunting, for centuries these frogs were sought after by hunters. As you might think, the hunters didn't want to eat the frogs, but rather, they captured them for their poison. They would add the poison to the tips of their hunting arrows, of course, nowadays most hunters use guns. These days dart-poison frogs are of less interest to hunters than to medical researchers. Researchers believe that they can make a new heart medicine from the poison, because it acts as a stimulant on the body's nervous system. Researchers think they could use it to stimulate a weak heart. There is, however, a problem with doing research on these frogs. Those that are caught in the wild will produce their poison until they die. However, those that are born in captivity, like the ones you see here, will not produce any poison at all.
如果你喜欢我们之前看过的多彩的动物，你肯定会喜欢下一种动物—青蛙。正常情况下，你也许不认为青蛙是彩色的，但很明显，这种青蛙是彩色的。它们是生活在美国中南部的箭毒蛙。看他们明显的色—经常是黄黑的条纹或者是深蓝的中带着黑色的斑点。 突出的肤色除了好看，还有一定的用途。这种颜色可以警告猎食者：“我是有毒的！”当受到威胁时，这种青蛙分泌一种有毒物质，这种毒物可以杀死任何想吃掉它们的动物。箭毒蛙通过它们的警戒色来传递这种信息，所以，大多数动物不喜欢捕猎箭毒蛙。 谈到捕猎，现在，近一个世纪以来，这种箭毒蛙一直在被捕猎。很明显，捕猎者不是为了吃箭毒蛙，而是为了他们的毒物。捕猎者把毒物涂在捕猎用的弓箭头上。当然，现在，大多数猎人用枪。 最近，医学研究者比猎人对箭毒蛙更感兴趣。他们认为箭毒蛙的毒液有刺激神经系统的作用，所以可以用来制作药物来刺激微弱的心脏。 然而，研究过程中也发现了问题。在野外补到的箭毒蛙会持续分泌毒物直到死亡。然而，被捕猎后出生的箭毒蛙压根不产生任何毒物。 ——译文来自: fanrong1985