科學研究發現 即使是無腦水母也會打盹
Humans are hardly alone in their need for sleep--as any cat owner knows. But what about other, very different animals?
人類絕非需要睡眠的唯一物種，任何一個養貓的人都清楚這一點。不過，對於那些與人類截然不同的其他物種呢？"In thinking about this…we wanted to use an evolutionary argument to figure out what is the simplest animal to sleep." Ravi Nath, a graduate student of biology and bioengineering at Caltech.
加州理工學院生物學與生物工程專業的研究生拉維·奈斯表示：“在思考這個問題（其他物種是否需要睡眠）時，我們想要從進化的觀點出發，找到需要睡眠的最原始生物。”"We decided to approach it from a conservation point of view, how conserved the sleep state is. And looked back into the animal tree and specifically looked at jellyfish," said Claire Bedbrook, also a biology and bioengineering graduate student at Caltech.
同爲加州理工學院生物學與生物工程專業的研究生的克萊爾·貝德羅克表示：“我們決定從行爲恆定的觀點處理這個問題--究竟睡眠有多古老。然後回溯動物種系進化圖譜，還專門研究了水母。”
Jellyfish have no central nervous system. "They do have neurons—their nervous system is a sort of loose set of neurons that control the animal's behavior. There's no control center."
水母沒有中樞神經系統。“它們的確擁有神經元，但是它們擁有的是一種控制動物行爲的彌散式神經系統。沒有控制中樞。”Nath, Bedbrook and the rest of their team worked with a species known as the upside-down jellyfish.
奈斯、貝德羅克和團隊中的其他成員一起研究了仙女水母。"Unlike jellyfish that we're probably most used to seeing in the wild, these jellyfish actually rest their bell on the seafloor, or in our case the tank bottom, and they pulse in place." These habits made this jellyfish easy to observe.
“與我們在野外常見的水母不同，這種水母其實會把傘膜搭在海底（在我們研究中是搭在水槽底部），並就地涌動。”該水母的這些習性令其易於觀察。
The researchers recorded the animals' behavior during the day and at night, to see if these jellyfish met the scientific criteria for sleep.
研究人員日夜記錄此水母的行爲，進而觀察它們是否達到了科學睡眠的標準。"Those three behavioral criteria are, first, that the animal goes through a period of quiescence where they are less active. The second is that during this quiescent state, the animals are not as responsive to environmental stimulus. And the third is that this quiescent state is actually necessary for the animal's well-being and survival."
“科學睡眠的三種行爲標準如下，第一，動物會經歷一段活動減少的靜止期。第二，靜止狀態期間，動物對環境刺激的反應性降低。第三，這種靜止狀態實際上對動物的健康和生存來講是很有必要的。”The observations revealed that these jellyfish do in fact sleep. That's a big deal because for scientists "there was this assumption in the community that you needed to have a certain level of complexity -- namely a central nervous system -- to actually sleep."
觀察結果顯示，該水母的確會睡眠。這可是個大發現，因爲對科學家來講，“科學界中存在這樣一種假設，即必需要進化到擁有一定程度的複雜性（如中樞神經系統）才能夠睡眠。”So what does this study tell us about why animals sleep, and how sleep evolved? Bedbrook says that although more work needs to be done, they have some ideas.
那麼，關於動物因何睡眠以及睡眠是如何發展的這兩個問題，該研究是如何回答的呢？貝德羅克表示，雖然仍需進一步研究，但是他們已經有一些想法了。"One hypothesis that we really like is that any animal that has neurons will have a sleep state, and that sleep might be an intrinsic property of neurons."
“其中有一種假設我們都很欣賞，即任何擁有神經元的動物均會出現睡眠狀態，同時睡眠或許是神經元固有的性質。”Nath agrees. "So neurons have a huge metabolic cost, and so maybe this period of sleep is a period of consolidated energy conservation that has evolved with neurons essentially."
奈斯對此表示認同。“由於神經元需要消耗大量新陳代謝的能量，因此或許這段睡眠時期，本質上是與神經元共同進化的一段統一的能量節約時期。”So nerves might be keeping you up at night—but having nerves is what's probably putting you to sleep.
因此，雖然神經緊張也許令你夜晚無法入眠，但正是因爲擁有神經，你才能夠睡覺。
