Welcome to brain Stuff, a production of iHeart Radio, Hey brain Stuff Lauren Bogle bomb here goldfish of the animals, not the crackers, are beautiful and inexpensive pets, and they're known for being pretty hardy, which is why many of us received one as an early pet, perhaps with less preparation and equipment than is actually required, which is why blacking an appropriate tank with a filter and water pump. Many of us checked in on our fish a few
days later to find it floating upside down, motionless. In our youthful innocence and curiosity, we might have wondered, is that how fish sleep? It's hard to tell when a fish is sleeping because they don't have eyelids, at least not ones that close completely over their eyes, obscuring their vision like ours do. But scientists know that fish do rest, and some have very interesting ways of doing it. A fish don't sleep the same way that you, or your dog,
or any other mammal does. Most don't seem to experience cycles of rapid eye movement or r e M, though, to be fair, we might just not know how to recognize dream stayed activity in these animals. For example, research on zebra fish suggests that they experienced similar brain activity to R. E. M sleep, and other researchers have observed an octopus changing colors while sleeping, which may suggest that it was dreaming. Still, scientists have observed that many species
of fish rest. This is a period of restoration when their metabolic functions slow and they're less active. A sufish, like reef sharks, lay still at the bottom of the
ocean or inside caves when they sleep. These sharks have a unique anatomical feature called a spiricle that forces water out of the sharks skills so that they can continue to breathe while they're resting, they're not as responsive to their surroundings, but some species of sharks and tuna must keep swimming to breathe because they don't have spircles to keep water flowing over their gills. In their cases, scientists hypothesized that they shut off half of their brains, which
is what dolphins do. They slow their breathing and move more slowly, but are still somewhat responsive to their environment. But some fish species, like the Spanish hog fish, are known to sleep very soundly, so soundly in fact, that divers can touch them and even move them to the surface without disturbing their slumber. Some relatively deep sleepers create their own protection. A parent fish, for instance, create enough mucus to form a cocoon around themselves at night when
they stop moving. This mucus blanket is likely used to keep blood sucking parasites from clinging to them while they sleep, and clownfish bury themselves in sea enemies to protect themselves from predators while they sleep. Like humans, fish have biological clocks that tell them when to be alert and awake and when to rest, and some sleep during the day
and some sleep at night. These tendencies primarily evolved based on when they're more or less likely to be attacked by predators or what the best times are to find a meal. One of the more bizarre sleeping habits of the ocean is experienced by loaches, which float to the top of the water and remain completely still when they sleep for short periods. So if your pet fish is a loach and it's motionless at the top of the tank,
it could very well be sleeping. Unfortunately, the same cannot be said about that pet goldfish, which tend to rest towards the bottom of their habitat, not upside down near the surface. Today's episode is based on the article do fish Sleep on how stuff works dot Com, written appropriately by Allison Troutner. Brain Stuff is production of I Heart Radio in partnership with how stuff works dot com, and
it's produced by Tyler Klang. For more podcasts my heart Radio, visit the heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows. M