Fish can live in very cold water. Of course, tropical fish from always warm rivers or warmed seas can never encounter lower temperatures in their lives, which will be disastrous for them.
However, oceanic fish, especially those species that live in the circumpolar waters, as well as the inhabitants of Russian rivers, lakes are very resistant to temperature extremes and their significant decrease. In the McMurdo Strait near Antarctica, the temperature indicator can drop below -2 degrees, but the fish is found there, and apparently, it does not suffer at all from the cold. Why do fish not freeze, and what allows them to show such resistance to temperatures?
Fish and their physiology
In order to understand the details, it is necessary to consider the physiology of fish. First of all, it is necessary to pay attention to the fact that almost all fish are cold-blooded creatures. Their organisms do not produce heat, and therefore the temperature indicator always corresponds to the temperature of the environment. That is, in warm bodies of water the fish will be warm, and in cold ones they will cool down to the rate possessed by the water around. It would seem that if this is the case, the fish should suffer from hypothermia and even freeze. Why do they not turn into a piece of ice at low temperatures, but continue to live, sometimes they behave quite naturally and actively?
It turns out that glycoproteins are present in the blood of fish that prevent freezing. Scientists found and studied these proteins in the middle of the 20th century. As it turned out, glycoproteins provide more than significant protection against freezing than any antifreeze that has been used by humans to this day.
Interesting fact: If you dissolve salt in water, it will freeze worse. However, glycoproteins are 200-300 times more effective than salts.
The effect of glycoproteins was controversial until recently, until this substance and its behavior in the body of fish were studied in more detail. Initially, it was believed that glycoproteins inhibit the development of ice crystals from intracellular and other body fluids, binding to the faces of barely appearing ice crystals.
However, recent studies have disproved these findings. It turned out that glycoproteins have a remote effect on water, or rather, on the dynamics of its molecules. If this substance is present in water, then the molecules order their movement, and the possibility of their bonding to the crystal lattice, which is necessary for the formation of ice, is minimized.
The action of these substances is so effective that they could make a breakthrough in modern science. It is not surprising that one of the German automobile corporations sponsored modern research - the automotive industry is in great need of such materials.
How do fish respond to lower temperatures?
Warm-blooded creatures run the risk of dying at lower temperatures.At least, prolonged excessive coolness is not too comfortable - both for humans and other warm-blooded ones. Under these conditions, warm-blooded people develop malaise, immunity falls, colds and other diseases can develop. However, cold-blooded fish do not face similar problems. Although lowering the temperature also affects their general condition.
So, if you watch the fish in the lakes and rivers of our country, you will notice that with cooling and lowering water temperatures they become less mobile, much more lethargic. They no longer need a lot of food and oxygen, which allows them to winter with minimal risks for the body.
As soon as the water bodies start to warm up again, the fish come out of suspended animation and begin to show more activity - many of them start their mating season, and then summer comes when you need to eat actively in order to create a certain supply of nutrients in the body for the winter.
Thus, the fish do not freeze, as they are cold-blooded creatures. Natural antifreezes are present in their blood, which exclude the formation of ice crystals inside the cells.
