Quallen schlafen wie Menschen – auch wenn sie kein Gehirn haben. Die Ergebnisse stützen die Theorie, dass sich der Schlaf zumindest teilweise entwickelt hat, um die DNA in einzelnen Nervenzellen zu schützen und dabei zu helfen, Schäden zu reparieren, die entstehen, während Tiere wach sind.
https://www.nature.com/articles/d41586-026-00044-7
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Jellyfish sleep like humans — even though they don’t have brains
Studying ancient sea creatures’ snoozing habits could shed light on the origins of sleep.
Neither jellyfish nor sea anemones have brains. But these animals sleep in ways strikingly similar to humans, according to a study published today in Nature Communications1. The findings bolster a theory that sleep evolved, at least in part, to protect the DNA in individual nerve cells, helping to repair damage that builds up while animals are awake.
“Neurons are very precious,” says study co-author Lior Appelbaum, a molecular neuroscientist at Bar-Ilan University in Ramat Gan, Israel. “They don’t divide, so you need to keep them intact.”
Previous work has shown that jellyfish enter a sleep-like state, but this study is the first to characterize the phenomenon in sea anemones, and the first to describe both creatures’ sleep patterns in detail. “Every time somebody adds to the list of species that sleep, it is a very important step for the field,” adds Chiara Cirelli, a sleep researcher at the University of Wisconsin–Madison.
For those interested, here’s the link to the peer reviewed journal article:
https://www.nature.com/articles/s41467-025-67400-5
i guess the question now is why their bodies can’t repair themselves while they’re awake.
Some people argue that almost all life has a kind of sleep, I don’t think it’s everything. But even some bacteria have day/night cycles.
It’s supporting another study I saw recently that said that mitochondria are the reason for the need for sleep: [Why do we need sleep? Oxford researchers find the answer may lie in mitochondria | University of Oxford](https://www.ox.ac.uk/news/2025-07-18-why-do-we-need-sleep-oxford-researchers-find-answer-may-lie-mitochondria)
> the team found that sleep is triggered by the brain’s response to a subtle form of energy imbalance. The key lies in mitochondria – microscopic structures inside cells that use oxygen to convert food into energy.
>When the mitochondria of certain sleep-regulating brain cells (studied in fruit flies) become overcharged, they start to leak electrons, producing potentially damaging byproducts known as reactive oxygen species. This leak appears to act as a warning signal that pushes the brain into sleep, restoring equilibrium before damage spreads more widely.
It’s quite interesting, I guess it’s a feature of our metabolism.