Monday, February 1, 2021

Evolution and Sleep

 From Live Science:

Sleep is near universal in the animal kingdom, seen in humans and all mammals, as well as in insects and even roundworms. However, all these creatures have some form of central nervous system, or brain, and so scientists didn't know whether the evolution of sleep preceded that of brains, or vice versa. Jellyfish, a relative of hydras that also lack a brain, have also demonstrated sleeplike behavior, Live Science previously reported. But the new study adds to these findings by showing that hydras not only sleep but also respond to the same molecules that regulate sleep in humans and other advanced animals.

"Based on our findings and previous reports regarding jellyfish, we can say that sleep evolution is independent of brain evolution," Itoh said. For the study, the researchers used a video-recording system — essentially a "hydra cam" — to monitor the hydras' movement and determine whether they had entered a sleeplike state, or a state of reduced movement that could be disrupted with a flashlight. They found that hydras had cycles of active and sleep states that lasted about four hours each. (Read more.)


No comments: