Why do fish sleep with their eyes open, and why do fish sleep with their eyes open

Sibler. Master] Note: Crocodiles are reptiles, not fish.

The answer to the question of why fish sleep with their eyes open is not absolute, because some cartilaginous fishes have an instantaneous fold equivalent to the eyelid that covers part or all of the eye, but most fish, such as carp, crucian carp, hairtail, and pomfret, do not have eyelids. Therefore, most fish do not close their eyes when they sleep, and a small number of fish sleep with their eyes closed.

Fish, like all vertebrates, sleep to relieve fatigue in the central nervous system and limbs, but how do fish sleep in a different position? This has to start with the structure of the fisheye.

There are about 20,000 species of fish in the world, and there are 2,500 species in China, whether it is a marine fish or not a freshwater fish, except for some cartilaginous fish such as true sharks that have instantaneous folds equivalent to eyelids, which can cover part or all of the eyes, other bony fish such as carp, crucian carp, hairtail and pomfret have no eyelids. Anchovies, breezy and mullets, such as anchovies, have fat-eyed faces, but transparent fish do not have eyelids, so it is difficult to tell if they are awake or asleep.

When fish sleep, they will stop swimming and stay in one place, but the length of time they stop swimming varies from fish to fish. However, as long as the fish is really asleep, reach out and grab the fish, just like a land vertebrate that is sleeping. There are also different layers of water in which fish sleep, some are on the bottom, some are in the middle layer, and some are sleeping on the bottom of the water, such as parrotfish.

Silver carp and silver carp like to take a nap under the aquatic plants in the summer afternoon.

Fish sleep is like a human nap, not for a long time, very alert, this is not only a fish but also other lower vertebrates sleep common characteristics.

How to distinguish fetal egg humidification in animals? It is mainly distinguished by the eyes (specifically the eyelids); Animals that move their upper eyelids down when their eyes are closed are viviparous; Animals that move their lower eyelids upwards when their eyes are closed are oviparous; The eyes that do not close their eyes and face are all wet, i.e., aquatic animals; If you don't close your eyes, your eyes are more prominent than your face, and they are all metaplasias, i.e., insects.

Fish are aquatic animals and do not have eyelids (some fish have transient membranes), so the eyelids are always open.

Fish sleep with their eyes open because they have no eyelids and cannot close their eyes when sleeping.

Fish live in the water for a long time, and due to the low light in the water, the fish's eyes become short-sighted, and they cannot judge the surrounding things through their eyes. Therefore, when the fish sleep, they stop the body organs to achieve the effect of sleeping and resting. When the fish swims sideways, floats up, or swings their tails, they are likely to be sleeping, and this is how the fish can rest themselves.

Sleeping properties of fish

1. Hide in the dark: Because fish may be attacked by predators when they sleep, they often choose some relatively safe places to hide, such as goldfish when sleeping, often near stones or aquatic plants. There are also some benthic fish that can hide themselves in the sand at the bottom of the water.

2. Secrete bubbles: In order to protect themselves while sleeping, some fish will secrete a gelatinous substance and wrap themselves in it. Don't worry about bubbles suffocating themselves because it will leave a hole in the mouth for water exchange and breathing.

3. Sleep while swimming: Some fish in the ocean have a relatively high metabolism and must always keep swimming, so they will not stop when they are sleeping. For example, sharks, tuna, etc., they also swim while sleeping, so it is difficult to tell whether they are awake or not.

Why do fish sleep with their eyes open

Fish are vertebrates and also need to sleep to eliminate fatigue of the nervous system and limbs, but fish do not have eyelids, so it cannot close its eyes when sleeping. Usually it sleeps in the dark, sometimes in the sand or in bubbles, and sometimes swims while sleeping, taking on a variety of different positions.

Fish float in the water to rest, appropriately stop the activity of various organs, or move slightly, which is called sleep swimming in fish physiology. The sleeping and swimming of fish varies, and some are in order to defend against the invasion of predators, and often gather into large groups; Others disperse in a certain range of activities, and then regroup at dawn the next day and continue to migrate forward.