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Speaker 1: Welcome to brain Stuff, a production of iHeart Radio, Hey

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Speaker 1: brain Stuff Lauren Bogle bomb here goldfish of the animals,

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Speaker 1: not the crackers, are beautiful and inexpensive pets, and they're

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Speaker 1: known for being pretty hardy, which is why many of

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Speaker 1: us received one as an early pet, perhaps with less

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Speaker 1: preparation and equipment than is actually required, which is why

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Speaker 1: blacking an appropriate tank with a filter and water pump.

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Speaker 1: Many of us checked in on our fish a few

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Speaker 1: days later to find it floating upside down, motionless. In

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Speaker 1: our youthful innocence and curiosity, we might have wondered, is

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Speaker 1: that how fish sleep? It's hard to tell when a

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Speaker 1: fish is sleeping because they don't have eyelids, at least

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Speaker 1: not ones that close completely over their eyes, obscuring their

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Speaker 1: vision like ours do. But scientists know that fish do rest,

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Speaker 1: and some have very interesting ways of doing it. A

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Speaker 1: fish don't sleep the same way that you, or your dog,

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Speaker 1: or any other mammal does. Most don't seem to experience

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Speaker 1: cycles of rapid eye movement or r e M, though,

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Speaker 1: to be fair, we might just not know how to

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Speaker 1: recognize dream stayed activity in these animals. For example, research

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Speaker 1: on zebra fish suggests that they experienced similar brain activity

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Speaker 1: to R. E. M sleep, and other researchers have observed

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Speaker 1: an octopus changing colors while sleeping, which may suggest that

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Speaker 1: it was dreaming. Still, scientists have observed that many species

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Speaker 1: of fish rest. This is a period of restoration when

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Speaker 1: their metabolic functions slow and they're less active. A sufish,

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Speaker 1: like reef sharks, lay still at the bottom of the

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Speaker 1: ocean or inside caves when they sleep. These sharks have

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Speaker 1: a unique anatomical feature called a spiricle that forces water

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Speaker 1: out of the sharks skills so that they can continue

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Speaker 1: to breathe while they're resting, they're not as responsive to

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Speaker 1: their surroundings, but some species of sharks and tuna must

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Speaker 1: keep swimming to breathe because they don't have spircles to

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Speaker 1: keep water flowing over their gills. In their cases, scientists

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Speaker 1: hypothesized that they shut off half of their brains, which

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Speaker 1: is what dolphins do. They slow their breathing and move

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Speaker 1: more slowly, but are still somewhat responsive to their environment.

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Speaker 1: But some fish species, like the Spanish hog fish, are

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Speaker 1: known to sleep very soundly, so soundly in fact, that

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Speaker 1: divers can touch them and even move them to the

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Speaker 1: surface without disturbing their slumber. Some relatively deep sleepers create

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Speaker 1: their own protection. A parent fish, for instance, create enough

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Speaker 1: mucus to form a cocoon around themselves at night when

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Speaker 1: they stop moving. This mucus blanket is likely used to

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Speaker 1: keep blood sucking parasites from clinging to them while they sleep,

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Speaker 1: and clownfish bury themselves in sea enemies to protect themselves

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Speaker 1: from predators while they sleep. Like humans, fish have biological

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Speaker 1: clocks that tell them when to be alert and awake

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Speaker 1: and when to rest, and some sleep during the day

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Speaker 1: and some sleep at night. These tendencies primarily evolved based

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Speaker 1: on when they're more or less likely to be attacked

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Speaker 1: by predators or what the best times are to find

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Speaker 1: a meal. One of the more bizarre sleeping habits of

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Speaker 1: the ocean is experienced by loaches, which float to the

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Speaker 1: top of the water and remain completely still when they

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Speaker 1: sleep for short periods. So if your pet fish is

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Speaker 1: a loach and it's motionless at the top of the tank,

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Speaker 1: it could very well be sleeping. Unfortunately, the same cannot

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Speaker 1: be said about that pet goldfish, which tend to rest

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Speaker 1: towards the bottom of their habitat, not upside down near

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Speaker 1: the surface. Today's episode is based on the article do

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Speaker 1: fish Sleep on how stuff works dot Com, written appropriately

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Speaker 1: by Allison Troutner. Brain Stuff is production of I Heart

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Speaker 1: Radio in partnership with how stuff works dot com, and

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Speaker 1: it's produced by Tyler Klang. For more podcasts my heart Radio,

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Speaker 1: listen to your favorite shows. M