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Fishes Found in the Mariana Trench Show Similar Genetic Mutations. Scientists Believe This Indicates Specific Adaptation to the Extreme Conditions of the Location
Deep-sea fishes have developed the same genetic mutation, even though they evolved independently and at different times. The discovery surprised scientists and revisits not only the power of natural selection but also the impacts of human activity in areas previously considered isolated.
Repeated Genetic Pattern in Different Species of Deep-Sea Fish
A new study published on March 6 in the journal Cell analyzed the DNA of 11 species of deep-sea fish. Among them were snailfish, barreleye fish, and dragonfish that inhabit the so-called hadal zone — ocean regions located more than 6,000 meters deep.
The researchers investigated how these species survived such adverse conditions: extremely high pressure, extremely low temperatures, and complete darkness.
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The fishes adapted with different skeletal structures, changes in circadian rhythms, and enhanced senses to live with little light — or even in complete darkness.
With the help of manned submarines and remotely operated vehicles, scientists collected samples from depths between 1,200 and 7,700 meters. The expeditions took place in the Mariana Trench in the Pacific Ocean and also in trenches in the Indian Ocean.
The Same Genetic Mutation Occurred Nine Times in Different Lineages
The genetic analysis showed that the eight lineages studied reached the depths of the sea at different times. Some date back to the Cretaceous period, about 145 million years ago.
Others evolved during the Paleogene, between 66 and 23 million years ago. And there were species that only reached these regions in the Neogene period, about 2.6 million years ago.
Despite this time difference, all species living below 3,000 meters showed a mutation in the Rtf1 gene. This gene controls how DNA is encoded and expressed. The mutation appeared at least nine times, separately, in different lineages.
According to Kun Wang, an ecologist at Northwestern Polytechnical University, this genetic similarity does not come from a common ancestor. It is a direct result of the extreme environment, indicating that similar conditions can lead to the same evolutionary response in distinct organisms.
Convergent Evolution: An Answer to Extreme Challenges
For Ricardo Betancur, an ichthyologist at the University of California in San Diego, who did not participate in the study, the finding is a clear example of convergent evolution. This occurs when different species develop similar characteristics as a way to adapt to similar environments.
“It is a powerful reminder that evolution often reuses the same limited set of solutions when confronted with similar challenges — in this case, adaptation to the extreme conditions of the deep sea,” stated Betancur.
This discovery reinforces the idea that the deep ocean exerts intense selective pressure on the species that inhabit it, shaping their biology in a surprisingly similar manner, even in distantly related lineages.
Industrial Pollutants Reach Even the Greatest Depths
In addition to genetic discoveries, scientists found worrying evidence of human pollution in deep ocean regions. In the Mariana Trench and the Philippine Trench, harmful chemicals were detected in samples of fish and seabed.
Among the pollutants were polychlorinated biphenyls (PCBs), used until the 1970s in electrical equipment, and polybrominated diphenyl ethers (PBDEs), which acted as flame retardants in consumer products.
PCBs were found in the liver tissues of hadal snailfish. PBDEs and PCBs themselves were present in sediments taken from over 10,000 meters deep in the Mariana Trench.
Contamination in Isolated Areas Catches the Attention of Scientists
Although previous research has already pointed to the presence of microplastics and chemical pollutants in the Mariana Trench, the new data shows that pollution has reached even deeper levels and with higher concentrations.
The study reinforces that not even the most remote places on the planet are free from the impact of human activity. Even in areas where life is nearly impossible, there are clear signs of human presence and interference.
With information from Live Science.
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