To avoid dissolution of nitrogen in the blood, sea lions when immersed driven supply air from the alveoli into the trachea, where gas exchange with the blood impossible. When it comes time to emerge, animals persecute the air back from the box into the alveoli, and thereby provide themselves with oxygen during ascent.

Zoologists have long puzzled over how aquatic mammals withstand sudden changes in pressure, and thus do not suffer from decompression sickness. It is known that at great depths under increasing pressure nitrogen dissolved in the blood, and when the pressure drops, that is, when a person or animal rise from a great depth, nitrogen again passes into the vapor state. If this process goes too quickly, the blood literally "boils" from coming out of gas, which is fraught with serious internal injuries that often lead to death.

Researchers from the Institute of Oceanology SCRIPPS (USA) managed to solve the riddle - at least for sea lions. The female California sea lion entered the special sensor, which tracked the oxygen content in the blood and simultaneously recorded the time and the depth of the animal. Then the animal was released.

According to researchers in a paper published in Biology Letters, at a depth of 225 meters from the sea lion was a sharp decrease in oxygen content in the blood: light of the animal collapsed and stopped the supply of gas. Compression of the lungs, reducing their size is a common phenomenon in aquatic mammals. After this sea lion for some time continued to swim under water and sank up to 300 meters. Then he started to emerge: at a depth of about 247 metres light again suppressed, and the concentration of oxygen in the blood rose. The total time of one such pochard averaged six minutes.

When pulmonary alveoli are compressed, they stop gas - and consequently, the nitrogen in the blood also misses. But how animals enough oxygen on the rise? It turned out that after compression of the lungs sea lions retain supply of air in the upper divisions of the respiratory tract - large bronchioles and trachea. The fabric of the trachea and large bronchioles cannot carry out gas exchange, and the air in them remains intact: no valuable oxygen, nor dangerous nitrogen in the blood flow can't get. Then when it comes time to surface, the air here is transferred back into the alveoli.

Most likely, similar mechanism of protection from decompression sickness use and other pinnipeds, but it will still have to check. Some of them (for example, sea elephants) to depths of up to one and a half thousand meters, and perhaps they have even more sophisticated techniques that let them not to choke and avoiding decompression sickness when lifting.

Prepared according to France Press.