Creatures that live in the dark may lose their sight over evolutionary time. They may even lose their eyes entirely. Now it appears that they also lose sleep. Because a new study shows that cave-dwelling fish spend more time awake than their ____1____ at the sunny surface. The finding is in the journal Current Biology.

Researchers studied ____2____ Mexican tetra in the lab. Fish that live in creeks or rivers have two eyes and see just fine. But those that have adapted to living in caves lack eyes. What they do have is ____3____. The scientists observed that the tetras that normally spend time in the light do sleep soundly at night, resting on the bottom of their tanks. The cave fish, on the other hand, ____4____, patrolling their habitats even after hours.

The researchers are working to identify the genes responsible for this fishy restlessness. Not that they’ll reveal how you can get by on minimal shut-eye. Because the cave fish may not need less sleep—they may need to stay awake to forage more in an environment where food can be scarce and appear ____5____. And even a blind fish can see: you snooze, you lose.
【視聽版科學(xué)小組榮譽出品】
counterparts three populations of insomnia remain on high alert unpredictably
在黑暗中生活的動物可能會在進(jìn)化過程中失去視力，甚至可能一點東西都看不見。但現(xiàn)在發(fā)現(xiàn)，它們有可能連睡眠都失去了，因為一項新研究發(fā)現(xiàn)，和住在光照充足的淺層同伴相比，住在穴居魚會更常保持清醒。這項發(fā)現(xiàn)刊登在《當(dāng)代生物學(xué)》雜志上。 研究人員在實驗室研究了三種墨西哥麗脂鯉種群。在溪里或河里生活的魚有兩只眼睛，視力良好。但穴居魚則沒有眼睛，而且患有失眠癥?？茖W(xué)家觀察發(fā)現(xiàn)，接觸陽光時長正常的魚類在晚上會在魚缸底部睡得很安穩(wěn)。而另一方面，穴居魚仍然保持高度警惕，三更半夜還在居住的地方游來游去。 研究人員旨在鑒別使魚類失眠的基因，而并不是說想展示如何在最小睡眠的狀態(tài)下活下去。因為穴居魚可能并不需要睡得更少——它們可能需要保持清醒，以便更經(jīng)常地在食物短缺和食物不常出現(xiàn)的環(huán)境中覓食。一條瞎眼魚都可以預(yù)見到：打個盹，你就虧了。