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Some people say that the ocean is another space. The ocean covers more than 70% of the earth's surface, with an average depth of about 3800 meters, while the deep sea deeper than 200 meters accounts for 93% of the total volume, and exploring the ecological geology of the ocean abyss plays an important role in the earth's ecology, earthquake prediction, and the origin of life.
In the Museum of Aquatic Biology of the Chinese Academy of Sciences, there is such a "star specimen" from the 7415 meters deep of the Mariana Trench - Pseudoliparis swirei (also known as mariana lionfish), collected by he Shunping, a teacher of the Abyss Expedition Team of the Chinese Academy of Sciences, which is not only the deepest fish found at present, but also because of its elegant appearance, it has changed people's impression of deep-sea fish "anyway, no one can see anyone, just grow up", attracting the interest of many visitors.
Specimens of the Svery lionfish on display at the Museum of Aquatic Biology
Belonging to pseudoliparis
The deepest part of the ocean, the mysterious Mariana Trench
Mariana Trench is located on the seabed of the northwest Pacific Ocean, located in Guam and the eastern part of the Northern Mariana Islands, is a narrow crack in the earth's surface, most of which is more than 8,000 meters deep and 11,034 meters at its deepest point, which is equivalent to filling in the entire Mount Everest and still more than 2,000 meters to reach the sea surface, known as the "fourth pole" of the earth in addition to the north and south poles and Mount Everest, and is a sacred place in the hearts of all deep-sea explorers.
Compared with space exploration, deep-sea exploration also has many problems that need to be overcome, such as pressure (every 10 meters of deep sea drop, the pressure increases by one atmosphere), signal transmission and seabed energy supply problems.
Schematic diagram of the Mariana Trench (Image: Wikimedia Commons)
Once thought that deep-sea conditions were not suitable for life, the development of scientific submarines was only realized after the First World War, and the exploration of the Mariana Trench did not really begin until 1960.
During explorations of the Mariana Trench in 2014 and 2017, researchers discovered and confirmed a new species of lionfish at a depth of more than 8,000 meters, the deepest known diving depth. In recognition of the results of extensive scientific collaboration, the scientists named the newly discovered fish after Herbert Swire, a sailor on the expedition that first discovered the Mariana Trench, and the Svery lionfish has officially entered the public eye.
The lionfish shot at a depth of 8,718 meters shows fish bones as bait that is eaten clean by deep-sea creatures
A veritable "face value"
Of course, "grow as long as you can't see it" is just the most common joke for deep-sea fish today, in the extreme environment of high pressure, lack of oxygen, lack of light, lack of food, they have specialized unique traits to adapt to difficult life, such as fangs and large mouths can greatly improve the efficiency of predation.
Chauliodus sloani is vertically distributed about 500-2500 meters
There is a continuous light emitter on the body, and its mouth can be opened to 120 degrees
Argyropelecus gigas
Habitat depth of 300-1000 meters, can control their own biofluorescence to match the light in the seawater to achieve "stealth"
The anterior dorsal fin of Caulophryne pelaglca (Caulophryne pelaglca) evolved into glowing fishing rods to attract small mobs as their food
Females are tens to hundreds of times larger than males, and after the male matures, the body organs will gradually disappear except for the sperm nest and become a fleshy protrusion on the female (Image source: Wikimedia Commons)
In contrast, the lionfish has more "eyebrow clear eye show". Their bodies are white and translucent, without scales, sharp teeth and large bodies, and their eel-like tails and wings are as wide and extended as the fins of a girl when they swim like a girl's skirt. In the waters where lionfish live, below 6,000 meters is called the ultra-abyssal zone, where there are almost no natural enemies, figuratively speaking, the pressure on each fingernail-sized place here is equivalent to the weight of an elephant, in addition to having to fight against complete darkness, temperatures close to freezing points and huge water pressure.
(Image from the Internet)
The "fluttering skirt" lionfish is attracted by the bait (image from the Internet)
"To soften the rigidity" - the great wisdom in the small body
Faced with the enormous pressure of the deep sea below 8,000 meters, how does the Mariana lionfish fight?
The enormous pressure of the deep sea is a challenge for most animals, and the coping strategy of the lionfish, like many deep-sea fish, is not to "carry hard", but to achieve survival by adjusting its own structure, so that the internal and external pressures of the body can be balanced to achieve survival.
Albatrossia pectoralis captured from the deep sea with expanded internal organs protruding into the mouth due to a sudden drop in extracorporeal pressure (Credit: Wikimedia Commons)
First, deep-sea fish can't use swim bladders to regulate buoyancy like shallow fish, they rely on certain lipids to provide buoyancy, and in order to reduce body density, they usually have small bones, less muscle tissue, and the body has a high water content, and the flesh is much like jelly.
Lionfish caught from 7,700 meters in the Japanese trench
In addition, the researchers found that deep-sea fish cell membranes are rich in unsaturated fatty acids, which are softer and more fluid. In addition, deep-sea organisms contain a lot of trimethylamine oxide (TMAO), which can help stop protein distortion, but when the depth exceeds 8200 meters, TMAO is also powerless, and this depth should be the survival limit of fish.
Of course, these are not enough, in the study of the Mariana lionfish genome, China's abyss expedition team found that the calcification process of its bones was terminated prematurely due to mutations in related genes, resulting in a very thin body bone and no closed cavity including the skull, at the same time, some cells and protein stability related genes also undergone specific mutations, which further enhanced the resistance of lionfish to pressure at the molecular level [11].
The incompleteness of the skull of the Mariana lionfish is associated with premature termination of the associated genes
"The Wisdom of Nature" and "The Wisdom of Science and Technology" - the birth of the bionic robot fish
Inspired by the Mariana lionfish, Professor Li Tiefeng's team of Zhejiang University applied the wisdom of nature to the exploration of science and technology, and the bionic soft robotic fish was successfully launched. The robot fish has a wing-like flexible pectoral fin and is driven by soft artificial muscles, while some hard devices such as control circuits, batteries, etc. are integrated into the gelatinous soft body, which can withstand the deep-sea still water pressure of 10,000 meters.
A large number of experiments have confirmed that the robot fish has a good application prospect in the deep sea, polar and other harsh and special environments, perhaps, when the technology of the bionic robot fish is fully mature and can be independently applied to the complex scene of deep-sea operations, the Mariana lionfish, the fish spirit in the abyss of the seabed, will no longer be alone.
Bionic lionfish soft-bodied robotic fish
Resources:
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12. Li, G., Chen, X., Zhou, F. et al. Self-powered soft robot in the Mariana Trench. Nature 591, 66–71 (2021).
Author: Xing Siqi, Wang Huanshan, Wang Xi
Source: Institute of Hydrobiology, Chinese Academy of Sciences, Museum of Aquatic Biology