英語(yǔ)聽(tīng)力文摘 帶紫外線的魚兒

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帶紫外線的魚兒

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嘍!(譯者注：此處“你”指動(dòng)物)畢竟傳遞基因才是進(jìn)化的意義之所在嘛!要傳遞基因就得有后代，要有后代你就必須得有足夠的吸引力，而且越光鮮閃亮越好。嘿!看這兒!我是不是很有吸引力呀?

嗯，這邏輯沒(méi)錯(cuò)，但是有個(gè)問(wèn)題。你越光鮮閃亮，被捕食者發(fā)現(xiàn)的可能性就越大。嘿!看那兒——那家伙真顯眼，我就吃它啦!

這就讓人為難了——怎樣才能既在異性眼中光鮮閃亮，又在天敵面前得以藏身呢?

新的研究表明劍尾魚已經(jīng)在進(jìn)化中找尋到了這個(gè)兩全之策，那便是使用紫外線。這些不起眼的小家伙事實(shí)上可以沿著兩側(cè)的魚鰭發(fā)出條紋狀的亮光——但是只能在波長(zhǎng)與紫外線的波長(zhǎng)相等時(shí)才能看見(jiàn)這種光。

來(lái)自德克薩斯大學(xué)奧斯汀分校的研究員莫莉·卡明斯和她的同事們做了一個(gè)有趣的實(shí)驗(yàn)。他們將一條雌性劍尾魚放入一個(gè)水槽中，并在其兩側(cè)分別放入一條雄性劍尾魚。但是，不同的是，他們把其中一條雄性劍尾魚用濾光玻璃給圍起來(lái)，而紫外線是無(wú)法穿透這種玻璃的。這樣便形成了一組對(duì)比：其中一條雄性劍尾魚的紫外線是可以被雌性劍尾魚看到的，而另外一條雄性劍尾魚由于被濾光玻璃阻隔，發(fā)出的紫外線便無(wú)法被看到。結(jié)果，他們發(fā)現(xiàn)，這條雌性劍尾魚對(duì)那條紫外線可見(jiàn)的雄性劍尾魚的興趣是另一條的兩倍。兩倍呀!這可是一個(gè)不小的發(fā)現(xiàn)!

之后，他們把墨西哥脂鯉(這種魚會(huì)捕食劍尾魚)取代雌魚放入中間的水槽，結(jié)果截然不同。脂鯉對(duì)兩條魚表現(xiàn)出同等的興趣，因?yàn)樗腿祟愐粯?，是無(wú)法用眼睛感知紫外線的。

再解釋一遍?簡(jiǎn)單說(shuō)來(lái)，就是雄性劍尾魚已經(jīng)找到了一種精細(xì)的方法，在吸引同類雌性的同時(shí)避免招致被吃的厄運(yùn)。