How jellyfish nod off just like humans

WORMS and fish can do it. So can bats, birds and bees. But now we know jellyfish can fall asleep too.

It had previously been thought that the sea creatures did not need to nap as they do not have a brain or nervous system.

But researchers at the California Institute of Technology found signs that they went into rest mode at night, pulsing less frequently than in the day. It means that sleeping must have begun very early on in their evolutionary history.

The scientists looked at a primitive jellyfish, called Cassiopea, which lives upside down on the sea floor. Resembling a miniature cauliflower head, its body pulses with a steady rhythm.

Video taken over 24 hours showed that they pulsed less frequently at night, Current Biology reports. But they could be woken up by dropping food in their tanks. Caltech’s Professor Paul Sternberg compared the effect of the food to that of smelling coffee in the morning.

The scientists also found that the jellyfish slowed down in the day if they were kept awake at night. Graduate student Claire Bedbrook said: ‘We might seem extremely different from jellyfish, but we both exhibit a similar sleep state.’