DO FISH EVER GO TO SLEEP

 Lacking eyelids, fish sleep with their eyes open, although some zebrafishh ave been found to suffer from insomnia.

Mankind has never discovered an animal that doesn't sleep, but you wouldn't know it by looking at fish. Every aquarium owner knows that no matter when you sneak a peek at a fish, it appears to be wide-eyed and awake. But that's because fish don't have eyelids, not because they are 24-hour lap swimmers. Yet even though all aquatic denizens need to nod off, at least some of them are susceptible to the same ailment that afflicts plenty of people: insomnia. According to researchers from Stanford University's School of Medicine, zebrafish can suffer from an inability to fall asleep.

The scientists have been studying sleep in all sorts of animals in the hopes of addressing the ills that plague people, but also as a way to
understand the entire mechanism of sleep. Zebrafish are ideal research subjects because their larvae are transparent, so scientists can see everything that goes on inside. One such discovery was a genetic mutation that appeared in those zebrafish that displayed insomnia. Lead researcher Emmanuel Mignot said the finding is a step toward treating sleep disorders. "The idea is to try to use this as an entry point to understand the neurobiology of sleep regulation," he said.