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Most fish do not have eyelids, so they cannot close their eyes. But does this mean that they are not sleeping?
The question of whether the fish sleep, it is easy to confuse even an experienced aquarium owner, not like an ordinary person. Most often this moment interests children, curious why.
So how do fish sleep and do they sleep at all?
A person is accustomed to having to close his eyes for sleeping. So do animals. It is advisable to be in the dark in a lying, relaxed position, although overworked people simply “turn off” in any position.
But to sleep with your eyes open is extremely difficult to imagine. Therefore, the thinking stereotype works: if it is impossible to close the eyes, then such a creature cannot sleep.
However, the inhabitants of the underwater world is not so. Eyelids for people and animals are needed in order to protect the eyeball from drying out.
Fish are in the water, so this danger for them simply does not exist. Water moisturizes and cleans the eyes of these creatures.
One can understand that the fish has fallen asleep by the following signs: it froze in the thickets or other secluded place, hung in the water column. Some may even lie down, and some species prefer to relax on their side.
Most species of fish prefer to sleep in the dark, so if you come to the aquarium and turn on the light, you will be able to notice how its inhabitants return to their awake state, waking up. But there are those who rest during the day.
These are predator fish, for example, catfish.
However, fish dream is not the condition that is meant by this word in humans. How do fish sleep? For them, this is not a state of complete relaxation and unconsciousness, as we do with you, but rather a process of slowing down the functions of vital activity.
This allows the fish to quickly become active, if something dangerous or edible has arisen nearby.
The phase of deep sleep, in which there is almost complete loss of contact with reality, is absent in fish. However, during sleep, there is a recovery in the work of the nervous system and other body functions.
Hang in the water column and drift during sleep can only fish that are of the type of bone. They manage to do this due to the presence of a swim bladder filled with air. The volume of air in this particular organ determines at what height the fish will be in the tank.
The smaller it is, the deeper it will sink into the water column. Most residents of home aquariums refers to the bone.
Ramps and sharks are cartilaginous fish, they have no swim bladder. How do fish sleep if they can’t hang in the water?
They are laid on the bottom or rest while driving. Antsistrusy and fights are considered cartilage fish suitable for keeping in an aquarium.
There are some underwater inhabitants who need to hide in a cave for sleeping. Parrot-fishes are sleeping very unusually – practically under a blanket.
Only as it they use mucus, which is released by the fish through the mouth. The mucus envelops the carcass, creating a protective cocoon in which you can safely rest and not be afraid of anything.
In the morning, the fish leaves their “blanket”.
As the fish sleep, it is important to know not only to satisfy their own curiosity, but also in order to provide the fish with comfortable living conditions. Like people, they do not like, if they violate their regime, they may suffer from insomnia, therefore:
- be sure to turn off the light in the aquarium at night;
- pick up the fish so that they sleep at one time of day.
There are species of fish that sleep during the day and prefer thickets for this. If you put these in your tank, during the day it will look empty and uninteresting.
Fish sleep or not :: how aquarium fish sleep :: Natural sciences
All animals need rest, but in appearance of some of them it is impossible to say whether they are sleeping or not. Similar difficulties are observed, for example, with fish.
Even during sleep, their eyes remain open, which often confuses people and prevents them from correctly interpreting the condition.
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Fish, like other representatives of the fauna, sleep. Only they do not close their eyes. This is because the fish simply do not have a century.
This difference from humans and terrestrial fauna is due to the environment in which they live. People have to constantly moisten the outer shell of the eye, blinking.
In a dream, this is very difficult to do, so the eyelids tightly cover the cornea, saving it from drying out. Fish live in water, which already does not allow their eyes to dry up.
Additional protection is not required.
Only some sharks have eyelids. During the attack, the predator closes his eyes, thereby protecting the eye from damage.
Sharks that have no eyelids roll their eyes.
At times, aquarists can observe how their pets lie on the ground or algae, freeze belly up or perpendicular to the bottom. However, it is necessary to make a sharp movement or turn on the light, as the pets begin to swim again, as if nothing had happened.
The sleep of all fish is very sensitive. Most species choose a quiet, secluded place to sleep, but everyone has their own habits.
For example, cod can lie sideways on the bottom, herring – hang in the water column head down, flounder – bury in the sand. Bright tropical parrot fish – great original.
In preparation for sleep, she builds a cocoon of mucus around her, which, apparently, does not allow predators to detect it by smell.
All types of fish, depending on the time of their activity, can be divided into day and night.
The structure of bone and cartilaginous fish is different. Cartilaginous fish, which include sharks and rays, do not have lids on their gills, and water enters them only during movement.
Because of this, they could not sleep peacefully. However, in the course of evolution, they managed to adapt and snatch their leisure hours. Some species have acquired sprinklers – special organs behind the eyes, with the help of which fish draw water in and direct it to the gills.
Others prefer to choose places to sleep with a strong bottom flow or they sleep, constantly opening and closing their mouths, thereby allowing water to saturate the blood with oxygen.
The katran shark that lives in the Black Sea sleeps on the move. The spinal cord is responsible for its movement, but the head can rest at this time.
Also, scientists believe that some representatives of cartilage fish can sleep in the manner of dolphins, alternately “turning off” the right and left hemisphere.
Can you sleep with your eyes open? No, you definitely need to close your eyelids to fall asleep.
Therefore, fish do not sleep like we do. They have no eyelids that they could omit. But with the onset of darkness, the fish also rest.
Some of them even lie on the side. Most fish rest calmly, which is similar to human sleep.
It’s like when people sleep, but they don’t cover their ears. Some fish rest during the night and feed during the day; others rest during the day and hunt at night.
Of course, aquarium fish and all other fish sleep. Somehow pay attention to the aquarium fish at night, they hang in a dark place and fall asleep, do not try to wake them abruptly, they can be stressful !! ! Here SOMIKI, for example, they sleep during the day, and at night swim out of a dark place (snag, stone house).
They do not sleep like we are not moving, but they hang in the same place and move their fins so as not to roll over to the top with a belly and not die! ! And they sleep with their eyes open, since they have no eyelids that would close their eyes! !