The mystery of the "connected couple" for a hundred years has been solved

you may have seen the catfish in the animated film "Under the Sea Mobilization", a face-catching, glowing deep-sea monster fish. The female has a glowing area on her forehead that looks like a pole with a light bulb hanging from it. These glowing experiences draw prey and potential mates to them.
fact, these are nothing, it is incredible that the breeding strategy of the herring: female and male fish "blood fusion", co-prosperity and symbone. This unusual phenomenon is known as "gender parasitic".
since Icelandic biologists discovered the first "consort couple" fish in 1920, the phenomenon of "gender parasiticism" has been a mystery for 100 years. Now, German and American scientists have solved this 100-year-old problem, according to a paper published in Science.
part of the reason is that it is difficult to collect well-preserved organizations to do the necessary research. Thomas Boehm, the study's co-author and director of the Institute of Immunobiology and Paleogenetics at the Mapu Society, told the China Science Journal.
researchers sequenced dna from frozen tissue specimens that covered a wide range of non-adhesive, temporary and permanently attached species of catfish. The researchers found that fusion species had significant changes in the composition and structure of key immune system genes compared to species that did not have attachment fusion. This gives researchers a deeper understanding of the immune system and helps develop treatments for immunodeficiency patients., also known as , are known to have 168 species that inhabit the depths of the ocean below 300 meters and have evolved some notable adaptability, the most impressive of which is how their husbands and wife get along. When people first discovered the creature, they were surprised that almost all of the fish were female. And almost all of the female fish have strange "lumps". Later, it was discovered that the "lumps" were male fish.
in order to survive, male mackerel bites the female when it encounters it and binds it together. These males are usually less than 10 mm long, attached to larger females, and mate through this sex parasitic.
For some species of herring, this attachment is temporary, while others are permanent: the skin tissue of the two fish merges, eventually connecting their circulatory systems and truly becoming "one" couples.
researchers say the permanent union of female and male fish represents an anatomical union that is virtually unknown in nature, except in the rare occurrence of genetically identical twins. The immune system is a common barrier that attacks foreign tissues like destroying cells infected by pathogens.
, why does the female's immune system turn a blind eye to "foreign invaders"?in other vertebrates, tissue fusion triggers a significant immune response, which is why people must take immunosuppressive drugs after receiving an organ transplant. Boehm always wanted to know how the catfish did it.
, Boehm and the herring expert Theodore W. Pietsch of the University of Washington in Seattle set out to study the genomes of different herring species.
they studied the structure of major tissue compatible (MHC) antigens. These molecules are present on the surface of human cells, which send warning signals to the immune system when they are infected by viruses or bacteria. To ensure that all pathogens are effectively identified, the diversity of MHC molecules is so high that it is difficult to find the same or almost identical form in any two individuals of the same species. This characteristic is also the root cause of tissue matching problems for human organs and bone marrow transplants.
researchers analyzed dna from 31 mackerel specimens from 10 species and found that the fused herring species lacked key immune system genes. The researchers say the genes that permanently attach to these MHC molecules have largely lost their independence, as if they had given up immune identification in order to fuse tissues.
addition to this unusual combination of MHC genes, we found that the function of killer T-cells, which are usually active in removing infected cells or attacking foreign tissues, is severely impaired during organ rejection. These findings suggest that the herring's immune system is unusual among thousands of vertebrates. "The study's lead author, Jeremy Swann of the Institute of Immunobiology and Paleogenetics of the Map Society, said.
these unexpected findings, scientists suspect that the recombination of the herring's immune system may be broader than expected. In fact, further studies have shown that antibodies, the second most powerful weapon in the immune defense arsenal, have also disappeared in some herring species.
, the researchers concluded that the animals used improved innity to protect themselves from infection, an unexpected approach. In fact, until now, it has been thought that once a partnership between innational and innational immunity has evolved, it has not been possible to get rid of this relationship, otherwise there will be serious consequences. As a result, the study showed that vertebrates could survive without adaptive immune function, which had previously been thought to be irreplaceable, despite the co-evolution of innitent immune function and adaptive function over hundreds of millions of years. addition to "husbands", catfish and glowing bacteria are also symbical relationships. Another group of researchers has previously found that the bacteria have lost some of the genes needed to survive freely in water. The paper was published in mBio.
, a microbiologist at Cornell University and lead author of the paper, said: "What is particularly interesting is the evidence that this evolution is still ongoing and that bacteria are still losing genes for reasons that are not clear.
Most known symbic relationships between organisms and bacteria are either hosts and free-living bacteria that cannot evolve to maintain symbic relationships, or host and in-cell bacteria, which live within host cells and significantly reduce the genome during evolution.
and bacteria represent a third symbic relationship, and preliminary data suggest that these bacteria may have been transferred from the herring to the water. "This is a new example of symbic relationships where bacteria are not actually trapped by the host, but they are evolving." Hendry told reporters.
genetic sequencing showed that the genomes of these glowing bacteria were 50 percent smaller than those of their free-flowing relatives, and that most of the genes associated with making amino acids and breaking down nutrients other than glucose had been lost. At the same time, they have a complete path to form whiplash - a spiral tail that moves through the water.
on the other hand, Boehm and others believe they have even caught a fish that is developing into a gender parasitic species. "It is noteworthy that we have found that unusual breeding methods in this species have been independently 'invented' several times," Pietsch said. "
, but how they evolved these breeding methods is not yet known." Very complex and requires more research. Boehm said.
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