In nature, there are many classes of different animals. One of them is fish. Many people do not even suspect that these representatives of the animal world have a brain. Read about its structure and features in the article.
Historical reference
Long ago, almost 70 million years ago, the oceans were inhabited by invertebrates. But fish, the first to acquire a brain, exterminated a significant number of them. Since then, they have dominated the body of water. The modern fish brain is very complex. Indeed, to follow some kind of behavior without a program is difficult. The brain solves this problem using different options. Pisces preferred imprinting when the brain is ready for the behavior that it sets at a certain point in its development.
For example, salmon have an interesting feature: they swim for spawning into a river in which they themselves were born. At the same time, they overcome great distances, and they have no map. This is possible due to this variant of behavior, when certain parts of the brain are similar to a camera with a timer. The principle of operation of the device is this: there comes a time when the diaphragm is triggered. The images in front of the camera remain on the film. So do the fish. They are guided in their behavior by images. Imprinting determines the personality of the fish. If you provide the same conditions, their different breeds will behave differently. In mammals, the mechanism of this mode of behavior, that is, imprinting, has been preserved, but the scope of application of its important forms has narrowed. In humans, for example, sexual skills have been preserved.
Brain sections of fish
This organ in this class has small dimensions. Does the fish have a brain? Yes, in a shark, for example, its volume is equal to thousandths of a percent of the total body weight, in sturgeon and bony fish, it is one hundredth, in small fish it is about one percent. The brain of fish has a feature: the larger the individual, the smaller it is.
The family of stickleback fishes that live in Mivan - the lake of Iceland has a brain, the size of which depends on the gender of individuals: it is smaller for the female, and larger for the male.
The fish brain has five sections. These include:
- The forebrain , consisting of two hemispheres. Each of them manages the sense of smell and schooling behavior of fish.
- The midbrain, from which the nerves that respond to stimuli depart, so that the eyes move. This is the center of view of fish. He adjusts the balance of the body and muscle tone.
- The cerebellum is the organ responsible for movement.
- The medulla oblongata is the most important department. It performs many functions and is responsible for various reflexes.
Parts of the brain of fish do not develop equally. This is influenced by the lifestyle of aquatic inhabitants and the state of the environment. So, for example, pelagic species, possessing excellent mobility skills in water, have a well-developed cerebellum, as well as vision. The structure of the fish’s brain is such that the representatives of this class with developed sense of smell are distinguished by the increased size of the forebrain, predators with good eyesight are medium-sized, sedentary representatives of the class are elongated.
Intermediate brain
He owes his education to visual mounds, which are also called thalamuses. Their location is the central part of the brain. The thalamus have many formations in the form of nuclei, which transmit the received information to the brain of the fish. In it there are various sensations associated with smell, vision, hearing.
The main function of the thalamus is the integration and regulation of the sensitivity of the body. He also participates in the reaction, thanks to which the fish have the ability to move. If the thalamus is damaged, the level of sensitivity decreases, coordination is impaired, and vision and hearing are also reduced.
Front brain
It contains a mantle, as well as striped bodies. The mantle is sometimes called a cloak. The location is the upper and lateral parts of the brain. The cloak has the appearance of thin epithelial plates. Striped bodies are located under it. The forebrain of fish is designed to perform functions such as:
- Olfactory . If this organ is removed from fish, they lose conditioned reflexes developed by stimuli. Movement activity decreases, attraction to the opposite sex disappears.
- Protective and defensive. It manifests itself in the fact that representatives of the Pisces class support a flocking lifestyle, take care of their offspring.
Medium Brain
It consists of two departments. One of them is the visual roof, which is called tectum. It is located horizontally. It has the appearance of swollen visual lobes arranged in pairs. In fish with a high organization, they are better developed than in cave and deep-sea representatives with low vision. Another department is located vertically, it is called tegmentum. It houses the highest visual center. What functions does the midbrain perform?
- If you remove the visual roof from one eye, the other goes blind. The fish loses sight when the roof is completely removed, in which the visual grasping reflex is located. Its essence lies in the fact that the head, body, eyes of the fish move in the direction of the food objects, which are imprinted on the retina.
- The middle brain of the fish captures the color. When the upper roof is removed, the body of the fish brightens, and if you remove your eyes, it darkens.
- Has a connection with the forebrain and cerebellum. Coordinates the work of a number of systems: somatosensory, visual and olfactory.
- The middle part of the organ includes centers that regulate movement and maintain muscle tone.
- The brain of the fish makes the reflex activity diverse. First of all, this affects the reflexes associated with visual and sound stimuli.
Oblong brain
He takes part in the formation of the trunk of the organ. The medulla oblongata is arranged so that the substances, gray and white, are distributed without a clear boundary.
It performs the following functions:
- Reflex . The centers of all reflexes are located in the brain, the activity of which provides the regulation of respiration, the work of the heart and blood vessels, digestion, and fins movements. Thanks to this function, the activity of the organs of taste is carried out.
- Conductor . It lies in the fact that the spinal cord and other parts of the brain conduct nerve impulses. The medulla oblongata is the site of passage of the ascending paths from the dorsal to the head, which go to the descending paths connecting them.
Cerebellum
This formation, which has an unpaired structure, is located in the back of the brain. The cerebellum partially covers the medulla oblongata. It consists of the middle part (body) and two ears (side sections).
It performs a number of functions:
- Coordinates movements and maintains normal muscle tone. If the cerebellum is removed, these functions are violated, the fish begin to swim in a circle.
- Provides the implementation of motor activity. When the body is removed, the cerebellum of the fish begins to swing in different directions. If you remove the shutter, the movement is completely disrupted.
- With the help of the cerebellum, metabolism is regulated. This organ affects other parts of the brain through the nucleoli located in the spinal cord and medulla oblongata.
Spinal cord
Its location is the nerve arches (more precisely, their channels) of the spine of fish, consisting of segments. The spinal cord in fish is a continuation of the medulla oblongata. From him to the right and left side between the pairs of vertebrae nerves depart. Through them, annoying signals enter the spinal cord. They innervate the body surface, trunk muscles and internal organs. What is the brain of fish? Head and dorsal. The gray matter of the latter is inside it, white is outside.