The upside-down jellyfish Cassiopea andromeda sleeps for roughly 8 hours a day.Credit: Shahar Shabtai/Alamy
Neither jellyfish nor sea anemones have brains. But these animals sleep in ways strikingly similar to humans, according to a study…

The upside-down jellyfish Cassiopea andromeda sleeps for roughly 8 hours a day.Credit: Shahar Shabtai/Alamy
Neither jellyfish nor sea anemones have brains. But these animals sleep in ways strikingly similar to humans, according to a study…