The floating bubble is a gas-filled protuberance of the front of the intestine, the main function of which is to ensure the buoyancy of fish. The swimbladder can perform hydrostatic, respiratory, and sound-forming functions.
It is absent in sailing vessels , as well as in bottom-living and deep-sea fish. In the latter, buoyancy is mainly due to fat due to its incompressibility or due to the lower density of the fish body, such as, for example, in antsistrusov , golomyanka and drop fish . In the process of evolution, one of the structures similar to the swim bladder was transformed into lungs of terrestrial vertebrates . The closest variant to four-legged lungs, however, is shown not by bony, but by bony ones ( multiheter having unpaired cellular lungs — lower pharyngeal outgrowth) and lactating fish (in three modern representatives there is a variation in the structure of lungs). After all, the lungs of land vertebrates originated from the lower outgrowth of the pharynx, and the bladder swim bladder — from the upper outgrowth of the esophagus.
Content
Swimming bladder in different groups of fish
The swimming bladder is not all groups of fish, and in those groups for which it is characteristic, there are species that have lost it in the course of evolution. The main modern large fish taxa with regard to the presence or absence of the swim bladder and its functions are characterized as follows:
Cyclotrate and cartilaginous - swim bladder is absent. Integral ( latimeria ) - swim bladder reduced. Lacrimonious , mnogoperovye - there is a respiratory organ. Cartilaginous ganoids ( sturgeon-shaped ) is a hydrostatic organ. Bone ganoids - there is a respiratory organ. Bony fish - there is, in some reduced, a hydrostatic organ, in a small number of species it is a respiratory organ.
Description
In the process of fish embryonic development, the swim bladder arises as the dorsal process of the intestinal tube and is located under the spine . In the process of further development, the canal connecting the swim bladder to the esophagus may disappear. Depending on the presence or absence of such a channel, the fish are divided into open and closed bladder. In open-bubble fish ( physostome ), the swim bladder is connected throughout the whole life with the intestine by the air duct, through which the gases come in and out. Such fish can swallow air and thus control the volume of the swim bladder. Carpies, herring , sturgeon, and others belong to the open-gum carp . In adults of closed-bladder fishes ( physo-sheets ), the air duct becomes overgrown, and gases are released and absorbed through the red body - the dense interlacing of blood capillaries on the inner wall of the swim bladder.
Hydrostatic function
The main function of the swim bladder in fish is hydrostatic. It helps the fish to remain at a certain depth, where the weight of the water displaced by the fish is equal to the weight of the fish itself. When a fish actively falls below this level, its body, experiencing greater external pressure from the water, compresses, squeezing the swim bladder. In this case, the weight of the displaced volume of water decreases and becomes less than the weight of the fish, and the fish falls down. The lower it falls, the stronger the water pressure becomes, the more the body of the fish is compressed and the faster it continues to fall. On the contrary, when ascending closer to the surface, the gas in the swim bladder expands and reduces the specific gravity of the fish, which further pushes the fish to the surface.
Thus, the main purpose of the swim bladder is to ensure zero buoyancy in the habitat zone of the fish, where it does not need to waste energy on maintaining the body at this depth. For example, sharks whose swim bladder is absent are forced to maintain the depth of their dive with constant active movement.
See also
- Submarine dive and ascent system
Links
- Swimming Bubble - an article from the Great Soviet Encyclopedia .
- Swimming bubble