Why are fish not afraid of cold?

Fish are not afraid of cold, because the cold air outside is blocked by ice, and the temperature will not be too low. In addition, they all make antifreeze proteins to help them survive in ice water.

Enzymes are protein that catalyze metabolic reactions, but their efficiency depends on temperature. Enzymes perform best at the best temperature, so as to maximize efficiency at different temperatures.

Some fish have evolved so-called isoenzymes, which perform the same function at different optimum temperatures. Other fish use alleles-different forms of the same enzyme controlled by different alleles, which makes the reaction proceed at different temperatures.

Extended data:

Fish is a kind of aquatic vertebrate with variable temperature. It breathes through gills, swims through the swinging of tail and trunk, and feeds on the upper and lower jaws. It belongs to the vertebrate subfamily of Chordata. Vertebrates are generally divided into fish (53%), birds (18%), reptiles (12%), mammals (9%) and amphibians.

According to the statistics of the late Canadian scholar Nelson in 1994, there are 246 18 species of fish in the world, accounting for more than half of the named vertebrates, and new fish species are constantly being discovered, with an average of about 150 species per year, which should increase by more than 1500 species in more than ten years;

There are about 32 100 named fishes in the world.