2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
Ichthyologists from the US National Oceanic and Atmospheric Administration (NOAA) have discovered the first fully warm-blooded fish. She turned out to be a representative of the genus of marine ray-finned fishes - Lampris guttatus, or ordinary fish. Unlike the already known warm-blooded fish such as striped tuna, some mackerel or mackerel or mako sharks, the fringes can maintain a constant temperature (on average 5 degrees Celsius above the environment) not only in skeletal muscles, but also in internal organs such as the heart. and the brain. The work was published in the journal Science. A press release is available on the NOAA website.
Previously, scientists from NOAA have already proven that the ovaries are able to maintain a constant temperature inside the skull. In a new study, they demonstrated that this effect extends to other internal organs, and also fully revealed the mechanism of thermoregulation.
It turned out that the main "heat generator" in the webs is the intensive movement of the large pectoral fins. They are associated with the largest muscles in the body of the fish. Their increased work causes a surge of metabolic heat and warming up of the venous blood.
It is known that all fish carry the main heat loss in the process of breathing, extracting oxygen from cold sea (or river) water through the gills. The heated venous blood is saturated with oxygen in the gills and, at the same time, quickly cools. However, in some fish, including the puff, this problem is cleverly solved. Their circulatory system is what as early as 1831 Georges Cuvier called rete mirabile - "a wonderful network" of closely intertwined veins and arteries.
The “Wonderful Network” works as a heat exchanger with oppositely directed flows of heat carriers (cold arterial and warm venous blood). The artery emerging from the gills branches into many thin vessels and is closely intertwined with the vessels of warm venous blood. Thin vessel walls allow heat to pass through easily. Therefore, the venous blood cools down inside the fish and there is almost no heat loss in the gills. And arterial blood, warmed up in the "wonderful network", enters the organs and tissues already warm.
Counterflow heat exchanger diagram
Common fish are rather large fish. They have a large oval and laterally flattened body. Because of this feature, in English they are often called "moon fish" or "sun fish", as well as "ocean pancake". Their weight reaches 270 kilograms, and their length is 2 meters. Improved thermoregulation allows them to hunt effectively in deep cold waters, where active pursuit of prey is not typical for other fish that prefer to wait and attack from an ambush. This is a significant competitive advantage that contributes to the survival and prosperity of the species.
Ichthyologist Nick Wegner with a common fry in his hands
The "champion" in thermoregulation among fish is striped tuna, capable of maintaining a body temperature of 27-28 degrees Celsius at a depth of 1 kilometer, where the water temperature is only 5 degrees Celsius. However, tuna maintain a high temperature mainly in striated muscle tissue, while their internal organs cool down rather quickly and slow down. In contrast to them, the puffs maintain, although not so high a temperature, but evenly throughout the body.