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 ...

Do fish with no eyelids sleep? Given that they spend their entire lives submerged in water, this is a reasonable question to ask. The short answer is yes, fish do sleep. But the way they sleep differs ...

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.

A large group of yellowfin tuna swimming off the coast of Italy. Like all fish, they sleep, but it's not like human sleep. Giordano Cipriani/The Image Bank via Getty Images From the goldfish in your ...

Why animals sleep has long puzzled scientists, although many studies suggest benefits to brain function, memory and learning. But linkurl:research;http://www.cell.com ...