Swim bladder

The swim bladder is an organ of teleost fish. It serves the specific weight of the fish to match that of the surrounding water, so the fish can float in water. It is made from an evagination of the foregut of the fish and constitutes a development of the lung fish with a change in function of a respiratory organ to a hydrostatic organ.

The air-bladder is also capable of stabilization, as is in the upright position because of the posterior (ie, in the body located above ) position of the air-bladder of the center of mass below the center of volume.

Most bony fish have a swim bladder. An exception is, for example, bullhead, so she moves mostly on the ground. Fish that do not have a swim bladder and still not among the ground-dwelling fish, such as sharks, have to generate lift by constantly swimming, or they reduce their bone skeleton and store fat, such as the ocean sunfish ( Mola ).

Filling of the swim bladder

There are two mechanisms for filling the swim bladder:

• Via swallowing of air in the air-bladder passes via the intestine ( in the Physostomen ).
• Through the blood vessels, which transport the gas dissolved by or to the gills. Fish that use this mechanism, called Physoklisten; they usually take place in deeper waters. However, many Physoklisten live as juveniles initially as Physostomen, ie for the initial filling of the swim bladder, it also comes with them first by air swallowing.

The miracle power of the swim bladder it comes to the following processes: by passive diffusion of oxygen from arterial (O2 - rich ) capillaries to the venous (O2 - poor ) capillaries prevents O2 from the swim bladder is excreted into the blood or will be recycled. The principle behind this is the counter-current principle, caused, compared with a bent tube, can diffuse through the O2 by an apex which is located on the floating bubble ( in the so-called red body ). The high O2 content of the swim bladder is produced by the obligate anaerobic ( glycolytic ) metabolism in the epithelial cells of the gas gland in the swim-bladder. The glycolytic lactate formed here has two effects: the salting-out effect and the Bohr effect. Lactate lowers the solubility of O2 in the blood, the pH is lowered by lactate. The two effects results in a O2 gradient, which fills the air-bladder.

Draining of the swim bladder

To empty the swim bladder, there are two different ways:

• The Physostomen use the so-called ductus pneumaticus, a combination of swim bladder and gills and intestine (and thus a connection to the outside world) to deliver the oxygen. The Physostomen sturgeon have neither the Oval still the red body and can still without air swallowing or leave the swim bladder volume ( slow) regulate.
• The Physoklisten use the so-called oval, a highly perfused area of the swim bladder to absorb gas back into the bloodstream. The surface of the oval and the Sauerstoffresorption associated is controlled by muscles.

Operation

The locomotion in water is due to the approximately 800-fold higher density and higher viscosity of about 55fach much more energy consuming and laborious than in the air. The density of animal tissues is greater than that of water, so water- living animals almost constantly need to perform swimming movements in order not to sink to the bottom. An organism with the density of water, however, could motionless floating in the water, thus saving energy of motion. It is therefore not surprising that one in aquatic animals different tissues or organs will, which are characterized by a particularly low density and thus bring the total organism of gravity closer. In order to keep the volume and the density of the bubble constant, a fish abtauchender gas must " secrete " in the swim-bladder. An ascent of fish gas from the bladder, however, must give, not because of the increasing bladder volume to lose density and shoot to the surface.

Physically similar acts of diving a free man, the more likely entrains much air only to plunge deep into the lungs and a scuba diver who readjusts its buoyancy compensator buoyancy at depth change with intake or exhaust of air and exhaling a precaution when emerging.

The swim bladder as a loud -forming organs

The swim bladder can be used on interior or exterior muscles also for phonation.

• Internal ( intrinsic) drum muscles ( muscle tone or sonic muscle) are in the swim bladder wall in toadfish and gurnard
• External ( extrinsic ) muscles drum (at least an approach to structures outside of the swim bladder ) Direct Type: The muscles are attached to the swim bladder, such as the transverse process of the spine, such as catfish
• Indirect type: The muscles do not put on to the swim bladder, such as piranhas. Some catfish families have a box spring apparatus.

The swim bladder as a respiratory organ

The swim bladder can also ( primary or secondary) serve as a respiratory organ, which enables them to fish to survive in periods of drought or low oxygen content of the water. This is the case eg when Arapaima or garfish ( Lepisosteus ).