For about a hundred years, scientists have known about the unusual way of reproduction of fish of the anglerfish or sea devils order. A tiny and weak (1-2 cm in length) male, when meeting a female, firmly bites into her body, after which an amazing process starts, during which the male loses his organs and turns into an appendage with testes on the female's body. For a long time, scientists could not understand how this is generally possible from the point of view of biology - the complete fusion of two different organisms?
On the one hand, we are seeing an alternative form of sexual parasitism, which is not new to the wild. On the other hand, it is a miracle that science can hardly explain. In the course of fusion, the circulatory and nervous systems unite in the male and the female, their tissues become common, and the female's body actually receives a new organ. And at the same time, there is no immune response that doctors face when trying to transplant any parts of the bodies of living beings. How is this possible?
Long-term study of the DNA of monkfish has shown that it lacks a number of the most important genes. In the body of this fish, there are no marker antibodies that detect foreign cells, it does not have T cells to destroy infected cells, and there are no histocompatibility antigens. Taken together, it looks like the devils in the course of evolution deliberately "turned off" their immune system so that males can mate with females and become one with them.
But how can a living being do without immunity, how does it protect itself from diseases? Some scientists believe that anglers still have immunity, but it is more complex and therefore has not yet been discovered. Others say that this is a different kind of discovery - it is quite possible that evolution has learned to create whole species of living beings that can easily do without immunity at all. True, they can live in strictly defined biomes with fixed conditions.