“There’s no way these jellyfish sleep,” she said, before joining them. To prove that jellyfish sleep, the students had to demonstrate that they fulfill three behavioral criteria. Over six days and nights, the researchers monitored 23 jellyfish, which pulsed about 30 percent less at night than during the day. The following day and night, the jellyfish exhibited much lower levels of activity than normal, suggesting sleep deprivation. But what we’ve found, at least in this jellyfish, is “you don’t need a brain to sleep,” Mr. Abrams said.

Source: New York Times September 21, 2017 16:01 UTC