Don’t mind me, I’m just taking a little jellyfish nap!
This is Sandra Tsing Loh with the Loh Down on Science.
Jellyfish don’t have a brain, just a spread of neurons. So why would they even need sleep?
Enter Raphael Aguillon and team from Bar-Ilan University. They discovered that jellyfish actually show human-like sleep patterns! About eight hours at night, plus midday naps!
Because jellyfish are transparent, their neurons are vulnerable to UV light. After exposure, the jellyfish slept longer. During the extra sleep, their damaged cells had time to heal! Even their DNA repaired!
Researchers think this repair process may explain why sleep developed.
No brain required! These jellyfish still know when it’s lights out!
Reference: Aguillon, R., Harduf, A., Sagi, D. et al. DNA damage modulates sleep drive in basal cnidarians with divergent chronotypes. Nat Commun 17, 3 (2026). https://doi.org/10.1038/s41467-025-67400-5