If a person has aquarium fish, he can constantly watch them awake. Waking up in the morning and falling asleep at night, people see how they slowly swim around the aquarium. But did anyone think about what they do at night? All the inhabitants of the planet need to rest and fish is no exception. But how do you know the fish are sleeping, because their eyes are constantly open?
What is a "fish" dream
Generally, speaking of sleep, one usually means the natural physiological state of the organism, when its response to the surrounding world is reduced, and the level of brain activity is minimal.
This happens in humans, mammals, birds, some insects and fish. On average, people spend a third of their lives in a dream (with a duration of sleep eight hours a day). In these time intervals, a decrease in heart rate and respiration occurs, the muscles relax. Such a state can be considered a period of inactivity.
But the fish are very different from the rest in biological functions of the body. Consequently, the dream they have is not quite familiar to us way.
- The environment in which they live, as well as the features of the external and internal structures do not allow them to completely disconnect from the surrounding reality.
- They do not have an absolute unconscious state, and they do not cease to fully understand the world around them.
- Their brain activity remains almost unchanged.
The sleep time of these underwater inhabitants depends on the type of fish. Those that are active during the day rest at night and vice versa. For example, a catfish hides all the bright time in a secluded place, practically does not move, and only at nightfall does it begin to swim and look for food.
What do the fish look like in a dream
Getting into the embrace of morpheus, the fish do not close their eyes. After all, they have no eyelids, and water constantly cleans their eye surface. However, the absence of eyelids does not interfere at all, since at night it is quite dark, and those fish that sleep during the day, specially swim to cover or shade the plants.
Fish that sleep can simply lie on the water, during which their gills will wash. Some can cling to the branches and leaves of plants. Other belly or side lay down on the bottom. Still others hang in the water column. In an aquarium, the sleeping fish most often drift at the bottom of the aquarium, making almost no movements, sometimes they can barely see the swaying tail. But with any, even the smallest effects of external factors (be it a danger or potential prey), they instantly revive and return to their normal state.
How to recognize a sleeping fish
Even if a representative of the water depths envelops sleep, she cannot close her eyes. Fish have no eyelids, so water always cleans the eyes. But such a feature of the eyes does not interfere with their normal rest. It is dark enough at night to quietly enjoy the rest. During the day, the fish chooses quiet places, which are penetrated by the minimum amount of light.
The sleeping representative of the marine fauna simply lies on the water, and the current at this time continues to wash the gills. Some fish try to cling to the leaves and branches of plants. Those who prefer to rest during the day choose a shade from large plants. Others like people lie sideways or belly down to the bottom. The rest prefer to stay in the water column. In the aquarium, its sleeping inhabitants drift and at the same time do not create any movement. The only thing that can be noticed at the same time is a barely visible swaying of the tail and fins. But as soon as the fish felt any influence from the environment, it returns to its normal state with lightning speed. Thus, the fish will be able to save their lives and get away from predators.
Sleepless Night Hunters
Professional fishermen are well aware that catfish or burbot do not sleep at night. They are predators and feed themselves when the sun is hiding. During the day, they gain strength, and at night they go hunting, while moving completely silently. But even such fish like to “arrange” their rest during the day.
An interesting fact is that dolphins never fall asleep. The current mammals were once attributed to fish. Dolphin hemispheres turn off for a while alternately. The first 6 hours and the second. also 6. The remaining time is both in waking state. This natural physiology allows them to always be in a state of activity, and in case of danger to escape from predators.
Favorite places for sleeping fish
During rest, most cold-blooded people remain motionless. They like to sleep in the bottom area. This behavior is characteristic of the majority of large species that live in rivers and lakes. Many argue that all aquatic residents sleep at the bottom, but this is not entirely correct. Ocean fish even during sleep continues to move. This applies to tuna and sharks. This phenomenon is due to the fact that the water all the time should wash their gills. This is a guarantee that they will not die from suffocation. That is why the tuna falls on the water against the stream and rests while continuing to swim.
Sharks do not have a bubble at all. This fact only confirms that these fish must always be in motion. Otherwise, the predator will sink to the bottom during sleep and, in the end, it will simply drown. It sounds funny, but it’s true. In addition, predators do not have special covers on the gills. Water can enter and wash the gills only while driving. The same applies to stingrays. Unlike bony fish, constant movement is, in some way, their salvation. To survive, you need to constantly go somewhere to swim.
Briefly hibernation in winter and summer
Some species of fish at the onset of the cold season fall into the so-called hibernation. These periods, of course, differ from what we are accustomed to understand under the dream. But, nevertheless, it is also a sleep cycle.
During it, the metabolic processes in the body also decrease, all physical functions slow down, and the fish is inactive. At this time, she either hides in the shelter, or remains at the bottom of the reservoir.
And there are those fish who prefer to sleep during periods of heat. So they are protected from dehydration. The phenomenon of summer hibernation plays a very important role, as it helps the fish to survive outside of the water during dry periods or when the temperature is too high.
For example, in Africa, there is fish that turns into mud, thus creating a cocoon, and in a state of complete rest is there up to several months, until habitat conditions become suitable again. It is worth noting that aquarium fish rarely resort to such methods.
Why is it so important to study the characteristics of sleep in fish?
For some, it’s just a desire to satisfy their own curiosity. How to sleep fish, you need to know first of all the owners of aquariums. This knowledge will be useful in providing suitable living conditions. As well as people, they do not like when their peace is disturbed. And some suffer from insomnia. Therefore, in order to ensure maximum comfort for the fish, it is important to observe several points:
- before buying an aquarium, think about the accessories that will be in it;
- there must be enough space in the aquarium to hide;
- fish should be selected so that everyone rested at the same time of day;
- At night, the light in the aquarium is better to extinguish.
Making sure that the fish are sleeping, and knowing how it looks like this, you can create a comfortable environment for your pets.
A couple of interesting facts about the dream of "wild" fish
In nature, these underwater inhabitants slumber differently:
- lying belly or sideways on the bottom, like cod;
- or up belly and upside down in the water, like a herring;
- or buried in the sand, like a flounder; or wrapped in mucus like a blanket, like a parrot fish.
The hardest thing to sleep is cartilaginous fish, especially sharks.
- They do not have a swim bladder, therefore, they cannot hang in the water, as they immediately sink to the bottom without movement.
- And they cannot lie on the bottom either, since they have not gills, but gill slits, in which water will not get into without movement, and the fish will simply suffocate.
What to do? Here’s what:
- some sharks adapted to sleep in places with a bottom current, constantly opening and closing their mouths for the movement of water around the gill slits;
- other species have sprinklers for this purpose (special gill openings located behind the eyes);
- and still others do sleep on the go. Their brain rests at this time, and the spinal cord regulates the swimming muscles.