Even Jellyfish SleepThree Caltech students have shown that these brainless animals have their own version of slumber.
Ed Yong Sep 21, 2017 Science
When Ravi Nath asks people if jellyfish sleep, he finds that everyone thinks they know the answer. Roughly half say yes, and half say no. Some scientists assert that only mammals and birds could be said to truly sleep. Other people think that even plants have something akin to sleep. “Every person we’ve asked has an opinion,” Nath says. “Even a 10-year-old kid has a response.”
Nath has an answer, too. Along with his friends and fellow California Institute of Technology students Claire Bedbrook and Michael Abrams, he put a jellyfish called Cassiopea through a gauntlet of clever experiments, which confirmed that they do indeed enter a sleeplike state. Every night, they become less active and less responsive. They can be easily roused from this state, but if they’re deprived of their slow periods for too long, they become even more inactive and unresponsive the next day—as if they were reeling from an all-nighter. And if the trio are right, their discovery has big implications for understanding both how sleep evolved—and why.
Sleep is widespread across the animal kingdom. Fish sleep. Flies sleep. Even nematode worms, which Nath studies, sleep. But jellyfish belong to one of the most ancient animal groups, which split off from those other creatures at least 600 million years ago. If they also have a version of sleep, it suggests that the roots of this behavior are more ancient than anyone suspected.
Do jellyfish dream of gelatinous sheep? No one can say.https://www.theatlantic.com/science/archive/2017/09/even-jellyfish-sleep/540432/
by seemslikeadream » Tue Jul 26, 2016 10:33 am 
