The article describes research published in the journal Science that shows that even jellyfish exhibit sleep-like behavior.[2] Scientists have found that jellyfish have periods of reduced activity during which they move less and respond more slowly to stimuli.[2] This "sleeping" behavior repeats itself in regular cycles, especially during the night, and the interruption of these periods leads to the jellyfish exhibiting "sleepiness", i.e. an increased need for subsequent rest.[2] The study shows that sleep is not an exclusive property of animals with a brain, since jellyfish do not have a brain, but only a simple nervous system.[2] The main finding is that the need for sleep may be a very old and fundamental biological trait that appears even in evolutionarily simple marine animals.[2]