All animals in the world are classified as warm-blooded and cold-blooded. The former include birds and mammals, and the latter include reptiles, amphibians and fish. But not the red-finned opa. This is the only representative of the fish group capable of thermoregulation.
The red-finned fish is a rather large fish, it grows up to two meters in length, and can weigh up to 100 kilograms. The fish itself is practically round and lives in warm seas at a depth of 100-400 meters. Its behavior is strikingly different from other predatory fish: the fish does not wait for its prey, but itself chases after it. By this he intrigued scientists, in particular Nicholas Wegner of the National Oceanic and Atmospheric Administration. He carefully studied the structure of the opal gills and found something strange in it.
Fish gills have two types of vessels: some drain blood from the body to saturate it with oxygen, while others transport oxygenated blood back to the body. But the veins have warm blood entering the gills. This fish is able to generate heat by energetically working with its fins while swimming, which speeds up its metabolism. Redfins are capable of maintaining their body temperature 5 ° C higher than the temperature of their surrounding water.
Also, Nicholas Wegner discovered that the vessels carrying warm blood are “wrapped” around the vessels that carry cold, oxygenated blood to the organs. Thus, the unique structure of blood vessels increases the temperature of the incoming blood before it enters the internal organs of the fish. This process is called countercurrent heat exchange and is similar to how car radiators regulate engine temperature, only there the process occurs in the opposite order. Thanks to the "built-in heating system", red-finned feathers can hunt in cold water, unlike many other predatory fish that have to look for warm water to keep warm.