Jellyfish sleep about as much as humans do – and nap like us too
The benefits of sleep may be more universal than we thought. We know it helps clear waste from the brain in humans, and now it seems that even creatures without brains like ours get similar benefits
Life
The benefits of sleep may be more universal than we thought. We know it helps clear waste from the brain in humans, and now it seems that even creatures without brains like ours get similar benefits
By Carissa Wong
6 January 2026
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An upside-down jellyfish in its natural habit on the seabed
Eilat. Gil Koplovitch
Jellyfish seem to sleep for about 8 hours a day, take midday naps and snooze more after a bad night’s sleep – just like us. Sleep is thought to have first evolved in marine creatures like these, and having a better understanding of their precise sleep patterns may help explain why it came about at all.
“It’s funny: just like humans, they spend about a third of their time asleep,” says Lior Appelbaum at Bar-Ilan University in Ramat Gan, Israel.
In animals with brains, such as mammals, sleep is crucial for things like storing memories and . But it was unclear why sleep evolved in jellyfish, which belong to a group of brainless animals called cnidarians, in which neurons – arranged in a relatively simple network across the body – are also thought to have first evolved.