How Do Fish Sleep?
鱼是怎么睡觉的？
曹艺凡 供稿
Sleep plays an essential role in our overall functioning, development, and how long we live. Without enough sleep, our health and cognitive performance suffers. The same goes for animals, including fish.
睡眠对我们身体的整体机能、发育和寿命长短有着至关重要的影响。缺乏足够的睡眠，我们的身体健康和认知能力就会受损。这对动物也是如此，包括鱼类。
While nearly all animals sleep, the way they sleep can be very different, especially in the case of fish. Fish sleep looks so different that many researchers prefer to call it rest instead of sleep.
虽然几乎所有的动物都会睡觉，但它们的睡眠方式大相径庭，特别是鱼类。鱼类的睡眠看起来如此不同，许多研究人员更愿意称其为休息，而不是睡眠。
Do Fish Sleep?
鱼会睡觉吗？
Many types of fish appear to sleep, but fish sleep differs from what we usually think of as sleep. Researchers have not been able to measure the familiar brain wave patterns that characterize human sleep and the sleep of many other animals in most fish, so researchers often refer to fish sleep as rest. Also, since most fish do not have eyelids, they can’t close their eyes during this rest.
很多种类的鱼似乎都会睡觉，但鱼的睡眠与我们通常所认为的睡眠不同。人类和许多其他动物在睡眠中会伴随有各种脑电波波形，但在大多数鱼类身上，研究人员尚未检测到类似波形。因此，研究人员一般把鱼的睡眠称为休息。此外，由于大多数鱼没有眼睑，它们在这种休息中无法闭眼。
Fish appear to be more alert than humans are during sleep, which may give them more time to react to potential threats in their environment. Still, fish do slow down metabolic processes in their resting state, much like humans. They physically slow down as well, with some fish floating in place.
鱼在睡眠期间看起来比人类更警觉，这样，它们就可能有更多时间对环境中的潜在威胁作出反应。然而，就像人类一样，鱼在休息状态下的新陈代谢还是会放缓。它们的动作也会减慢，有些鱼会漂浮在适宜的地方。
How Do Researchers Know That a Fish Is Sleeping?
研究人员如何得知一条鱼在睡觉？
Since fish do not look very different when they are asleep, it can be difficult to determine whether a fish is resting or awake. However, during a state of rest, fish are much less responsive. Some may appear to stop moving completely, and can even be touched or handled without waking up.
由于鱼在睡着的时候看起来没有什么不同，所以很难确定一条鱼是在休息还是醒着。但在休息状态下，鱼的反应能力要弱得多。一些鱼可能看起来完全不动，甚至在被触碰或拿起来的时候都不会醒过来。
Moreover, some fish are more vulnerable to being attacked by predators at night, which suggests that they are diurnal, or resting and less alert at night. Studies have found that certain fish species experience more deaths in the first two hours after sunset, which indicates that these fish tend to fall asleep at that time.
此外，一些鱼在夜间更容易受到捕食者的攻击，这表明它们主要在白天活动，在夜间会进入休息状态因而不太警觉。研究发现，某些鱼类在日落后两小时的死亡数量更多，表明这些鱼在那个时间段更容易进入睡眠状态。
A lack of responsiveness is often a sign of fish sleep, but researchers have found additional markers of sleep that fish share with humans and other animals. For example, studies show that melatonin may regulate the sleep-wake cycles in zebrafish. Zebrafish also appear to have distinct stages of sleep like humans, and follow a circadian rhythm.
缺乏反应能力通常是鱼类进入睡眠的标志，但研究人员发现了鱼类和人类以及其他动物所共有的其他睡眠标志。例如，研究表明，褪黑素或许可以调节斑马鱼的睡眠—觉醒周期。斑马鱼似乎也像人类一样拥有明显不同的睡眠阶段，遵循着昼夜节律。
The Stages of Fish Sleep
鱼类睡眠的不同阶段
Humans cycle through four stages of sleep, including two stages of light sleep, one stage of slow-wave, deep sleep, and one stage of rapid eye movement (REM) sleep. Although fish do not have a neocortex like humans, researchers were able to monitor the brain activity, heart rate, and eye and muscle movement in zebrafish to document two stages of sleep that are similar to slow-wave sleep and REM sleep.
人类睡眠可以分为四个阶段，包括两个轻度睡眠阶段、一个慢波深度睡眠阶段、以及一个快速眼动（REM）睡眠阶段。尽管鱼类不像人类那样拥有大脑新皮质，但研究人员还是能够监测到斑马鱼的大脑活动、心率、眼睛和肌肉运动，记录两个与慢波睡眠和快速眼动睡眠相似的睡眠阶段。
When fish do not get enough sleep, they seem to be vulnerable to the effects of sleep deprivation. After a night of sleep deprivation, zebrafish experience a sleep rebound, in which they catch up on sleep.
当鱼没有得到足够的睡眠时，它们似乎很容易受到睡眠不足的影响。整夜的睡眠不足会使斑马鱼出现睡眠反弹现象，在这个过程中它们会补足睡眠。
This resting state is so essential to fish that they will find ways to maintain a bare minimum of sleep, just like other animals. For example, if fish are subjected to experiments in which their sleep is interrupted, they will eventually nod off into microsleeps, managing to obtain at least 5% to 10% of their normal amount of sleep.
这种休息状态对鱼来说是非常重要的。它们会像其他动物一样，想办法维持最低水平的睡眠。例如，如果鱼经历了睡眠被打断的实验，它们最后会打瞌睡至微睡眠模式，从而获得至少5%—10%的正常睡眠量。
【Vocabulary】
1. predator n. 捕食者
2. diurnal adj. 日间活动的
3. melatonin n. 褪黑素
4. circadian adj. （指每24小时人或动物体内变化）昼夜节律的，生理节奏的
5. neocortex n. （大脑）新皮质
6. deprivation n. 缺乏；剥夺
7. rebound n. 反弹
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