英语听力文摘 English Digest 358、带紫外线的鱼儿（在线收听）

Ultraviolet Fish
带紫外线的鱼儿

So you want to attract a mate. After all, passing on your genes is what evolution is all about. To do that you need offspring, and to get a lot of those you need to be attractive. The flashier the better. Hey, look over here! Sexy me.

Ah, but there’s the problem. The flashier you are, the more likely you are to attract predators. Hey, look over there–that guy really stands out. I’ll eat him.

This is a pickle. How can you be flashy in the eyes of mates but subdued in the eyes of predators?

New studies show that swordtail fish have evolved a clever solution: use ultraviolet light. These innocuous little critters actually shine brightly in stripes that run along their flanks-but only if you look in the UV wavelength.

Researcher Molly Cummings and her coworkers at the University of Texas at Austin placed a female swordtail in a tank with two males visible at either end. One of the males, however, was surrounded by filtering glass that blocks UV light. They found that the female was twice as likely to demonstrate interest in the male whose UV flashers were visible to her. Twice as likely! That’s a big finding.

Put a Mexican tetra in the middle tank–that’s a predator who snacks on swordtails–and you get a different result. The tetra shows equal interest in getting at both swordtails. Like humans, tetras are unable to register UV light.

Interpretation? Male swordtails have developed a subtle way of advertising sexual readiness to females of their own species-while avoiding courting disaster.

 

 

 

 

 

那么你是想吸引配偶喽！（译者注：此处“你”指动物）毕竟传递基因才是进化的意义之所在嘛！要传递基因就得有后代，要有后代你就必须得有足够的吸引力，而且越光鲜闪亮越好。嘿！看这儿！我是不是很有吸引力呀?

嗯，这逻辑没错，但是有个问题。你越光鲜闪亮，被捕食者发现的可能性就越大。嘿！看那儿——那家伙真显眼，我就吃它啦!

这就让人为难了——怎样才能既在异性眼中光鲜闪亮，又在天敌面前得以藏身呢？

新的研究表明剑尾鱼已经在进化中找寻到了这个两全之策，那便是使用紫外线。这些不起眼的小家伙事实上可以沿着两侧的鱼鳍发出条纹状的亮光——但是只能在波长与紫外线的波长相等时才能看见这种光。

来自德克萨斯大学奥斯汀分校的研究员莫莉·卡明斯和她的同事们做了一个有趣的实验。他们将一条雌性剑尾鱼放入一个水槽中，并在其两侧分别放入一条雄性剑尾鱼。但是，不同的是，他们把其中一条雄性剑尾鱼用滤光玻璃给围起来，而紫外线是无法穿透这种玻璃的。这样便形成了一组对比：其中一条雄性剑尾鱼的紫外线是可以被雌性剑尾鱼看到的，而另外一条雄性剑尾鱼由于被滤光玻璃阻隔，发出的紫外线便无法被看到。结果，他们发现，这条雌性剑尾鱼对那条紫外线可见的雄性剑尾鱼的兴趣是另一条的两倍。两倍呀！这可是一个不小的发现！

之后，他们把墨西哥脂鲤（这种鱼会捕食剑尾鱼）取代雌鱼放入中间的水槽，结果截然不同。脂鲤对两条鱼表现出同等的兴趣，因为它和人类一样，是无法用眼睛感知紫外线的。

再解释一遍？简单说来，就是雄性剑尾鱼已经找到了一种精细的方法，在吸引同类雌性的同时避免招致被吃的厄运。