Fish, fame is very early. Their unique predation has long been talked about - the modified dorsal fin resembles a fishing rod and can glow as bait.
The reason why these sea anglers can shine depends on symbiotic bacteria. There is enough evidence to suggest that these bacteria are gradually acquired from the marine environment by salmon during their growth, and it is a difficult process.
After gaining the ability to shine, the symbiotic story about the salmon is far from over.
Species of the deep-sea horned catfish family (Ceratiidae) have evolved extreme sexual dimorphism—males orders of magnitude smaller than females in symbiosis with females much larger.
They each achieve the same goal in several different ways: "soft rice and hard food".
Eat soft rice hard
When scientists first began catching horned salmon, they noticed that all the specimens were female. Moreover, almost every individual has something that appears to be a parasite attached to it, ranging from as few as one to as many as 7 or 8.
Eventually, biologists determined that the "parasites" were male horned catfish.
As an adaptive response to the vast depths, the horned catfish evolved a heterogeneous symbiosis. In the deep sea, encounters between two sexes are rare, and when they meet, they cannot be let go.
In order to catch the female, the male horned fish adopt the strategy of "soft rice and hard eating" - biting the first female they encounter.
After biting into the female's skin, the male releases an enzyme to digest its own and the "rich woman's" skin, fusing the two at the vascular level.
For the rest of his life, males receive nutrients through "marital property"—a shared circulatory system—rely on the female host to survive, and provide sperm to females in return. As long as females are alive, they stay alive and maintain reproductive function.
There are many tricks
The 2005 edition of "Deep-Sea Fish Research" described that different species of horned salmon evolved different means to quickly "catch" females.
Some species have small eyes and are not suitable for identifying females, but at birth, males are already equipped with very developed olfactory organs that can detect odors in water; While other species, whose nostrils are underdeveloped and less likely to efficiently find females by smell, they have huge and highly specialized eyes, which (probably) help identify mates in dark environments.
It should be emphasized that the symbiosis of soft rice and hard eating is not the only means of reproduction of horned salmon, and in many species, it is only an optional strategy.
If the male meets the female at the point when his gonads are not yet mature, then he will adopt the soft rice strategy of "hard eating" and biting the symbiosis of the alliance for a lifetime, similar to the mechanism of "a child boy looking for an adult woman".
When males and females meet when they are mature, it has been observed that most species mate normally to lay eggs and then separate.
The biologists' hypothesis is that all this is related to whether there is a scarcity of environmental food and the density of salmon populations. They themselves judge in a way that humans do not yet understand whether to use the traditional method of fish reproduction, or bite to death for a lifetime.
The science of immunity behind the symbiosis of the association
Symbiosis occurs in nature, and only known examples of horned catfish are known.
But in human labs, scientists began artificially creating symbiosis as early as the mid-18th century—surgically linking two living organisms, mostly lab mice, together to form a single, shared physiological system.
Ethically, these experiments are rather "evil". But for more than 200 years, such experiments have not stopped.
After all, the symbiosis experiment has provided humans with a large amount of research data on metabolism, radiation, aging, and blood exchange between young individuals, and has been translated into results that will actually help humans. (It has also become a source of evil inspiration for many film and television works, such as human centipedes)
The life span of the experimental subjects combined with surgery is extremely short-lived, and the mutual attack and phagocytosis of immune cells between individuals is a typical problem. Therefore, as the only symbiosis that exists in nature, scientists have obtained the treasure and invited the salmon into the laboratory.
In 2021, scientists studying epigenetics and immunoscience performed DNA analysis on 31 specimens from 10 species under the family Ceratoceratidae.
The results showed that all fused individuals were deficient in key immune system genes, specifically, the immune system key that allows antibodies to mature and produce T-cell receptors.
Multiple males can fuse with a single female—unable to produce functional antibodies and T cells that can often repel foreign invaders and distinguish an individual's own cells from unfamiliar ones.
Somehow, their immune systems seem to allow symbiosis in a compromised form and are not subjected to other ill effects.
Write at the end
A closer look at how salmon harness this technique can have important implications for the human world, such as breaking the restrictions of blood transfusion, rejection of organ transplants, etc., making human repair more convenient.
Author thanks for your attention (- _-)