Add Yahoo as a preferred source to see more of our stories on Google. A protective mucous cocoon surrounds this parrotfish as it sleeps in Australia's Great Barrier Reef. This layer of protection ...

You’re staring at your aquarium. It’s late. Everything is quiet. And there’s your fish, floating calmly, fins moving slowly, eyes wide open. Are they... asleep? Or just zoning out? Fish don’t come ...

Fish don’t have eyelids. They don’t curl up in beds or snore, so it’s easy to assume they just keep swimming forever without rest. But they do sleep—it just looks very different from how we do it.

The short answer is yes, fish do sleep. But the way they sleep differs from land-dwelling creatures. Unlike humans who have eyelids, fish don't close their eyes when they sleep. Instead, many species ...

Tom has a Master's degree in Journalism. His editorial work covers anything from archaeology and the environment to technology and culture. Tom has a Master's degree in Journalism. His editorial work ...

Humans and other mammals cycle through distinct sleep phases. One of them is easily recognized by the darting motion of the eyes behind closed lids, giving it its name: REM (rapid eye movement) sleep.

Despite decades of research, scientists admit that they still have a lot to learn about sleep. In general, sleep can be defined as a period of reduced activity that is relatively easy to reverse.