Fish can not be separated from the water, leaving the water will undoubtedly die, this is both a natural phenomenon, but also a natural law. However, the world is so big that there is nothing strange about it. There is such a fish on the African continent, which not only does not die immediately after leaving the water, but can survive for up to five years without eating or drinking, this fish is the African lungfish.
In the African savannah, whenever the dry season comes, the grasslands have little precipitation, coupled with the hot weather, the evaporation is extremely large, and all the rivers, lakes and even swamps become dry. At this point, the African lungfish burrows into the deep mud and curls up until its tail is almost bent to its head.
After that, the African lungfish stop eating and reduce the consumption of various organs of the body to a minimum, entering a dormant state. It can last for six months without eating or drinking until the rainy season comes. In extreme cases, African lungfish can survive up to five years out of water.
It is said that an African brother dug up dirt from the ground in front of his house to build a house, and accidentally put an African lungfish into the wall. Five years later, the mud wall collapsed and dried African lungfish fell to the ground and were found by the African brothers. He put the dried fish into the water, and unexpectedly, a few seconds later, the dried fish magically came back to life and swam away alive in the water. This shows how amazing the African lungfish is!
As we all know, fish die after leaving the water not because of thirst, but due to lack of oxygen. Fish breathe on gills, which contain a large number of capillaries. Water flows from the mouth of the fish into the gills and then flows out from the trailing edge of the gill cap, completing the gas exchange. Once the fish leave the water, the gills will bond to each other, reducing the area in contact with the air, which will lead to hypoxia and suffocation. So, don't African lungfish worry about lack of oxygen after they leave the water?
There are actually several species of lungfish, including Australian lungfish, American lungfish, African lungfish and so on. In the nineteenth century, Aboriginal Australians often ate lungfish as salmon. Once, Creft, the curator of the Australian Museum, noticed a "salmon" on a plate during a meal and found that it had a lung on its abdomen.
Kreft immediately dissected the fish and found that the lung length was almost as long as the body cavity of the entire fish. A fish has lungs inside its body, which means it can breathe with its lungs. Later studies found that the fish could breathe with both gills and lungs, as well as lungs and gills at the same time.
In fact, the lungfish has two sets of respiratory systems, it breathes with its gills when it is in the water, and when the river dries up in the dry season, it will hide in the mud and breathe with its lungs. After drilling into the mud, a layer of mucus oozed from the epidermis of the lungfish's body, coating its body with a lining between the mud hole. The four corners of the lungfish's mouth are also formed like a round funnel by this mucus, leaving a small hole to go straight to the outside, allowing air to enter inside, and using the lungs to breathe weakly.
Because of its ability to breathe with its lungs, this fish got its name "lungfish". However, the name "lungfish" is actually not worthy of the name, because the lungs of the lungfish are not really "lungs", but should be called swim bladders. For the vast majority of fish, the role of the swim bladder is mainly to help the fish float or sink, enhance the balance of the body, and breathing is done through the gills. The special thing about the lungfish is that it can breathe not only through the gills, but also through the swim bladder. The structure of the swim bladder is very similar to the lungs and can exchange gases, so some people call the lungfish's swim bladder "primitive lung".
The maw of the lungfish is very developed, and the anterior part of the entire swim bladder is merged into a single chamber, which is very short in length, and then splits into pairs, reaching the posterior end of the body cavity. The lateral wall of the central cavity in the bladder forms many small air chambers (alveoli) of varying sizes, and each small air chamber is re-divided into many small air sacs (alveoli), which are very similar in structure to the lungs of terrestrial animals. Because its swim bladder has the function of a lung in terms of physiological structure, it is full of branched vascular networks and spiral lobes, with short swim bladder tubes that communicate with the esophagus, and can absorb oxygen and excrete carbon dioxide with the swim bladder when there is a lack of oxygen.
In addition to breathing with their lungs, African lungfish can also rely on the fat stored in their bodies to maintain their lives during the dry season, and if necessary, turn their muscles into nutrients to maintain life. In addition, the dormancy of the lungfish is the sleep of the whole cell, and even its heartbeat will almost stop, and it can reduce its metabolism to 1/60 of its normal state.
African lungfish are also one of the oldest surviving "living fossils" on Earth, first born 300 million years ago. In ancient times it was a resident of the ocean, and in the middle and late Devonian period, it began to march to land, into the freshwater environment, and eventually became a freshwater fish.
The breeding method of African lungfish is also very special. The average fish spawn in the water, while the African lungfish lay their eggs in a mud nest. After the female lungfish releases the eggs, the male lungfish are cared for. In order to enable the offspring to have a good growth environment, the abdominal fin of the male lungfish grows many microvascular-rich filamentous protrusions as soon as the reproductive period is reached, and the oxygen in the blood is released into the water through these filamentous protrusions to facilitate the normal development of the eggs.
Since the hibernation of The African lungfish is a kind of cellular level sleep, scientists use this as a breakthrough to hope that humans can also sleep in the future, so as to win time for ultra-long-distance space travel or medical rescue.
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