The strange strategy of the hookfish for reproduction may have played a role in its evolution

Hookfish live in the deep sea, and finding a mate in that dark area is not an easy task at all; But once they find their mate, they never let go. After finding a suitable mate, the male fish will usually bite her belly and stay attached until his body is completely fused with his mate’s body. The unique sexual strategy of deep-sea anchovies may have helped their ancestors move into entirely new habitats, allowing for today’s astonishing diversity of species.

to report New Scientist, Chase Brownstein From Yale University and his colleagues, the evolutionary process of more than 160 species of deep-sea hookfishes or ceratids (Ceratiidae) were reconstructed. Known for their large jaws and their ability to lure prey with luminescence, ceratids are a subgroup of the larger order of anemones. Rock anchovies and exotic fish such as puffer fish, sea toads and batfish are also members of the order of anchovies.

Parasitic lifestyle Hooked fish It helped them to enter the deep sea habitat

Using genetic sequencing, Braunstein’s team found that the ancestors of hookfish walked on the sea floor on their pectoral fins. But 55 million years ago, some of these fish began swimming in the vast deep-sea region of the ocean, or the “midnight zone.” Thus, over a five-million-year time period, swimming crayfish enjoyed greater genetic diversity than their cousins ​​on the sea floor.

Elizabeth Miller “It’s strange, because the seafloor and reefs are usually home to more diverse species,” says UC Irvine. Environments with more topographic complications make living organisms in the environment more complex. “But the deep sea region, with its constant temperature and vast expanses of empty water, is actually the most homogeneous habitat on Earth.”

Miller and colleagues late last year A genealogy of different species of hook fishes they built. Although Miller’s team and Brownstein’s team used different methods, the studies of both groups are largely based on the time course and the scale of the diversity of hookfishes in the deep sea.

Braunstein’s team found that this surprising diversity may be due to the ciratids’ parasite-like reproductive strategy; Thus, a small male using its jaws It connects to a much larger substance And it remains in this state until the female is ready for mating. In some species, male and female mate permanently and even share a circulatory system. This unique mating method is theoretically useful for deep-sea hookfish; Because it is unlikely that they will encounter another member of their own species in their lifetime.

Braunstein’s analysis showed that the presence of some traits to create this parasitic trait and evolutionary mutation Hooked fish At Deep sea region of the ocean its necessary; Such as the difference in body size between males and females and the weakness of the immune system in the female which does not harm the male.

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“Major parts of this complex trait, before displacement,” says Brownstein Hooked fish It also existed in the deep sea. Sexually parasitic method rather than essentially as gas in the engine [تنوع] Acting slowly is like preparing the gas pedal.

Miller says it’s “probable” that a parasitic lifestyle helped hookfish enter the deep-sea habitat, but how they achieved such wide diversity after the habitat change is still unclear.

This question will be difficult to answer, especially when recovering flawless samples fish hook It is difficult from the depths of the sea. But researchers say having two comprehensive genealogies will help other researchers do more research.

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