Jellyfish and sea anemones sleep just like us
Sea anemones and jellyfish do not have brains, but the way their neurons behave during sleep shows striking similarities to those of humans.
Humberto Ramirez via Getty Images
Jellyfish and sea anemones are curious creatures: these organisms have evolved no brain and, as scientists have discovered over the past few years, humans do not need to sleep. However, animals have neurons—nerve cells that appear to be interconnected throughout the body. And now new research shows that the way these animals sleep is remarkably similar to human sleep, suggesting that sleep may have evolved before even the most primitive brain.
The results, published Tuesday in the journal Natural communications, will also help answer one of the main mysteries of science: why do animals sleep? They add to past evidence from other animals and humans that sleep provides a “window” to maintain brain and body function, helping to repair DNA damage and maintain healthy neurons.
“This confirms that sleep opens a window to perform key household tasks,” says Philip Morren, an assistant professor of psychiatry and behavioral sciences at Stanford University who studies sleep. Morren was not involved in the new study.
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The new work shows that this function of sleep has been conserved across evolution, he says, from animals such as primates, which have some of the most complex brains. cnidariansfor example jellyfish, which do not have them.
Interestingly, the study shows that jellyfish seem to enter a sleep-like state for about eight hours a day and usually at night, a schedule that many people may be familiar with. Sea anemones also sleep for about a third of the day.
The researchers also showed that when these animals' neurons were subjected to additional command-induced damage, they slept more. This discovery, Morren says, provides clues to what makes us fall asleep in the first place.
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