SLEEP patterns vary widely among species. The most common assumption is that sleep is a requirement for all those with a brain since sleep is important to a number of brain functions, including how neurons communicate with each other. But is sleep only dedicated to those with a brain? Do jellyfishes also go to sleep?
Verdict:
TRUE
In a research published by the journal Current Biology, it is found that one species of jellyfish, Cassiopea, apparently sleeps and has the same trouble we do waking up.
It is unclear which is the bigger surprise: that an animal without a brain sleeps, or that in the daytime, it’s capable of being awake.
These are the first brainless animals known to show sleep-wake cycles, but not the first invertebrates.
In invertebrates, the sleep-like state has been observed in some species of coelenterates, nematodes (roundworm), annelids, arthropods, and mollusks.
According to Ravi Nath, a Caltech graduate student who studies this sleep-like state in C. elegans, though jellyfish sleep is exactly the same as human sleep, it has many of the same core features but, as an example, there is no obvious analog of REM sleep—the period where our closed eyes flicker rapidly, our muscles relax, and our brains conjure vivid dreams.
The study’s co-author Claire Bedbrook added that they would also be keen to identify if there are other species of jellyfish or sea sponges which do sleep.
References:
2. https://www.livescience.com/
3. https://www.sciencefriday.com/
4. https://www.theatlantic.com/
5. https://www.livescience.com/
