Jellyfish Can Sleep Like Humans, Researchers Find

Greek Reporter ^ | January 8, 2026 | Abdul Moeed

[nickcarraway]

Jellyfish and sea anemones, despite lacking brains, show sleep behavior similar to that seen in humans, according to a new study published in Nature Communications. Researchers found that these simple marine animals, like jellyfish, experience periods of rest that align closely with human-like sleep, offering new insight into how sleep functions in creatures with nervous systems but no centralized brain.

The study revealed that the upside-down jellyfish (Cassiopea andromeda) sleeps for about eight hours daily, primarily at night, with a short rest during the day. The starlet sea anemone (Nematostella vectensis), which was studied in a lab setting, also showed daily rest patterns for roughly a third of the day, mostly near dawn.

These observations were made both in controlled environments and in natural habitats, such as the waters near Key Largo, Florida.

Sleep function in brainless animals offers new clues

Lior Appelbaum, a molecular neuroscientist at Bar-Ilan University in Israel and co-author of the study, explained that neurons are delicate structures that do not regenerate through cell division.

He said preserving their integrity might be one reason sleep exists. The findings support the theory that sleep helps repair damage to DNA in nerve cells, which can accumulate during waking hours.

Earlier research had confirmed that jellyfish enter a sleep-like state. However, this study is the first to document sleep behavior in sea anemones and to provide a detailed comparison of the two species’ rest patterns.

Chiara Cirelli, a sleep researcher at the University of Wisconsin–Madison, emphasized that identifying sleep in additional species adds valuable evidence to the field and strengthens the argument that sleep plays a fundamental role in biology.

Jellyfish and sea anemones show signs of human-like sleep

Although sleep exposes animals to risks like predators and environmental threats, scientists agree it must serve an essential purpose, as it has been preserved through evolution across a wide range of species.

Ravi Nath, a postdoctoral neuroscientist at Stanford University, noted that there is strong evidence linking the emergence of sleep to the development of neurons, and that different species have adapted the function to fit their unique needs.

By studying jellyfish and sea anemones, researchers continue to uncover how sleep evolved and why it remains vital even in the absence of a brain.

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TOPICS: Pets/Animals; Science
KEYWORDS: anemone; dreamlikeajellyfish; godsgravesglyphs; sleep

[nickcarraway]

Do jellyfish dream of electric sheep?

[dfwgator]

[frank ballenger]

The jellyfish are grateful to Mike Huckabee for insisting that Bill O’Reilly ask the company to give away one month bottles of Relaxium to 1,000 jellyfish. “Sleep is the foundation of a jellyfish’s life.” 🪼🪼🪼🪼💊💊💊💊

[Jeff Chandler]

On their sides?

[kiryandil]

Now we know how Republicans sleep...

[nickcarraway]

They are trying to cut back on screen time before bed.

[Getready]

Floating around “sleeping” and defenseless in an environment of hazards and predators is not a good survival trait. One would think that the mutation which allows that behaviour would have been weeded out long, long time ago. N’est pa?

[alexander_busek]

Finally, this mystery of the ages has been solved!

Now, I'll finally be able to sleep nights again.

Regards,

[alexander_busek]

Floating around “sleeping” and defenseless in an environment of hazards and predators is not a good survival trait. One would think that the mutation which allows that behaviour [sic] would have been weeded out long, long time ago. N’est-ce pa?

Same ought to apply also to higher animals - incl. humans - nicht wahr?

Regards,

[Getready]

I believe that “behaviour” is the British English spelling...and when speaking the French...n’est-ce pas is pronounced as “n’est pah”..but good catches anyway. I spelled it as I say it...but it was a mistake.
Nicht wahr?
Freegards.

[Adder]

I dunno...when I do that my tentacles get all tangled...doesn’t seem to bother them.,..

I sleep more like a monkey...little nest building...a little cuddle with the nest mate...seems to work better.

[ClearCase_guy]

The jellyfish sleep with Luca Brasi.

[equaviator]

Do jellyfish have their own version of melatonin? Maybe there’d be a market for it as a sleep aid gummy, and if it’s shaped like colorful jellyfish then kids might want to bug their parent(s) to buy it at 7-Eleven and Wawa store checkout counters. /s

[Salman]

Like humans? Really? Do they dream? { snicker }

My speculation -- "Like humans" is a bit of journalistic flair added by an "educator".

[The_Media_never_lie]

Jellyfish Can Sleep Like Humans, Researchers Find

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Do jellyfish prefer king, queen or double mattresses?

[whitney69]

If they can cure joint pain with green lipped muscles then they can make you sleep with essence of jellyfish. It’ll be advertised soon using possibly John Walsh mucking his oyster bed and flaunting his multi million dollar beach side homes in Australia and Hawaii. And his wife will be feature digging clams.

wy69

[alexander_busek]

I sleep more like a monkey...little nest building...a little cuddle with the nest mate...seems to work better.

I sleep like a baby... a little crying... a little wetting.

Regards,

[alexander_busek]

If they can cure joint pain with green lipped muscles then they can make you sleep with essence of jellyfish. It’ll be advertised soon using possibly John Walsh mucking his oyster bed and flaunting his multi million dollar beach side homes in Australia and Hawaii. And his wife will be feature digging clams.

Went right over my head!

If you're going to make obscure references, you might at least include a short, explanatory pictorial!

Regards,

[ZinGirl]

They wale up every few hours to use the bathroom and sometimes can’t get back to sleep so they turn on the nightstand lamp and pull out a book? Wow. Crazy. Didn’t know they could read.