Can warm-changing animals have a fever?
No one likes fever. Fever often makes people feel weak and dizzy. Although fever is painful, it is a large-scale elimination of harmful bacteria and viruses in the body. From this perspective, fever is a good thing. Some scientists even say that a normal frequency of fever can regularly eliminate pathogens including bacteria and viruses, reducing the risk of cancer.
Fever is usually caused by bacterial or viral infection. When there are too many bacteria or viruses infecting the body, the body’s thermoregulatory system will raise the body temperature, increase the activity of the enzymes related to the autoimmune system, enhance your own immunity, and defeat these “invaders”!
However, fever is only the “welfare” of warm-blooded animals. Thermostatic animals have evolved a thermoregulation system that can maintain a constant body temperature, and the thermoregulation system can increase the body temperature as needed to cause “fever.” Since the temperature-changing animal does not have a regulating system to maintain a stable body temperature, its body temperature generally changes with changes in the environment. Of course, temperature-changing animals also have heat-generating structures, but the heat generated by their bodies is not enough to maintain a constant body temperature, let alone a fever. So how do warm-temperature animals fight the virus? This answer may make you laugh out loud—basking in the sun or bathing in hot springs! When invaded by pathogens, cold-blooded animals often choose to bask in the sun or bathe in hot springs to raise their body temperature and stimulate the body’s immune system to resist pathogens. This behavior is called behavioral fever.
The phenomenon that temperature-changing animals use behavioral fever to eliminate pathogens is widespread, and scientists can observe it in the laboratory. A few years ago, a scientist did such an experiment: a water tank was divided into three parts: the left, middle, and right parts, and the temperature of these three parts was divided into 24°C, 28°C, and 32°C through instrument adjustment. This part has an interface connection, and the fish can walk through to each part in turn. 24°C is the ideal temperature for carp, 28°C is relatively hot, and 32°C is the temperature that can make carp “fever”. Scientists placed a bunch of healthy carps on the left part of the tank. After a while, they found that almost all carps still stayed on the left part. Even if some carps swam to the middle and right part, they finally swam back again—perhaps staying there. I feel uncomfortable in the middle and right parts. After that, the scientists took out the healthy carp and placed a bunch of carp infected with herpes virus in the left part of the fish tank. After a while, most of the carp actually swam to the right of the fish tank this time. What’s surprising is that none of these carps that should have died have used high temperature to improve immunity, thereby controlling and eliminating the herpes virus.
Why is there a warm-blooded animal?
People have always thought that the emergence of warm-blooded animals is because they have the biggest advantage that thermo-changing animals can’t match-temperature adaptability. It can adapt to large temperature changes, has a wider range of activities, and is more conducive to survival. This statement seems credible, but unfortunately, there is no evidence that the evolution of temperature-changing animals is due to this. In addition, warm-blooded animals often need to consume at least several times the energy of warm-temperature animals of the same quality in the same time. This is also a major drawback of evolution. Some people think that temperature-changing animals only need to stay in a suitable temperature environment, and there is no need for such complicated and energy-intensive evolution.
The latest speculation of scientists believes that the purpose of the first step in the evolution of a temperature-variable animal into a warm-blooded animal is actually just to resist infection by pathogens.
Temperature-changing animals use behavioral fever to eliminate pathogens, but this requires an external heat source, such as the sun or hotter water. But the heat source is not easy to find at all times-hot springs are hidden in corners you don’t know. Even things that are easily accessible like sunlight may be covered by thick dark clouds, causing them to appear for several days or even dozens of days. In cloudy weather, the pathogen infection for such a long time may kill the animal.
Therefore, scientists speculate that in order to resist pathogens in a more timely and convenient manner, certain temperature-changing animals have evolved themselves into warm-blooded animals so that they can stimulate immunity through their own fever. It can be said jokingly that perhaps the warm-blooded animals are created to have a fever.
Perhaps, although the thermoregulation system of warm-blooded animals has brought them many survival advantages, these advantages are probably not the original purpose of thermo-temperature animals, because evolution is always going on and layered. The environment in each period will be different, and the course of evolution will always be adjusted. Evolution only addresses a specific problem at the time and cannot be changed.
Of course, this statement is a fairly new hypothesis, which needs further research.