Snoozing jellyfish have proved you don’t need a brain to sleep
The Cassiopea could be “woken up” by scientists placing food in their tank.
Snoozing jellyfish have confirmed that a brain is not necessary for sleep.
Scientists made the discovery after observing a primitive jellyfish called Cassiopea that lives upside down on the sea floor and lacks any kind of central nervous system.
The creatures, which resemble miniature cauliflower heads, have bodies that pulse with a steady rhythm.
But they could be “woken up” by dropping a little food into the tanks where they were kept.
“It’s the first example of sleep in animals without a brain,” said US researcher Professor Paul Sternberg from the California Institute of Technology (Caltech).
He compared the effect of the food to that of smelling coffee in the morning.
At night it took them three times longer to recover and return to a resting position. Such “grogginess” was typical of sleeping animals, said the scientists.
The researchers also found that the jellyfish slowed down during the day if they were kept “awake” by having tiny jets of water fired at them at night.
“We might seem extremely different from jellyfish, but we both exhibit a similar sleep state.”
