In a paper published last week in the journal Current Biology, scientists have shown that at least some jellyfish sleep. This discovery is noteworthy as jellyfish are simple organisms that do not have brains, but rather a network of nerves. To prove that the jellyfish they were studying sleep, the scientists needed to prove three behavioral criteria, which they did.

Also noteworthy, the scientists discovered that melatonin, a common sleep aid for humans, makes the jellies sleepy as well.

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