In the rivers of Africa, the Americas and Australia, there is a rare animal between fish and amphibians, the lungfish. It appeared 40,000 years ago in the Devonian period, covered with tile-like scales, the dorsal fin, fin and tail fin are all connected together, and its swim bladder is structured much like a lung, which can exchange gases, so it is called lungfish.
Because its prostitute has the function of a lung in terms of physiological structure, it is full of branched vascular networks and spiral lobes, with short tubes that communicate with the esophagus, and can absorb oxygen and excrete carbon dioxide in the absence of oxygen. Interestingly, the African lungfish also has the ability to hide itself deep in the mud during the dry season, and uses the surrounding mud to build a very strong "small mud hole", opening a small breathing hole in the front of the mouth, and it lies quietly in it and sleeps for up to 6 months of dry season. When the rainy season comes, it breaks out.
If there are camels in the desert, then the lungfish in the African desert are comparable to camels, which can not drink water for 3-5 years, and there are rumors that an African resident dug up the African lungfish that is still tenacious and alive in the house he built for 4 years, which makes the inspirational story of the lungfish widely circulated in the folk.
Lungfish that turn on sleep mode also excrete waste in their bodies, so how do they excrete? In general, fish living in water excrete metabolite ammonia through the osmotic pressure difference with the water body, and the ammonia concentration in the fish body is higher than the ammonia concentration in the water body, which is conducive to ammonia discharge. Lungfish living on land, because there is no water around, can only find another way, like most organisms on land, convert metabolites into urea and excrete them.
But sometimes, even if the lungfish have the ability to resist drought, they still can't escape the fate of being killed. In the eyes of local residents in Africa, the lungfish sleep season is their feeding season, and many residents will dig them out of the soil. Even if the lungfish leaves the water, it is still using its weak body to fight against nature, but it is no match for human hands.
Lungfish have been a variety of species, there have been more than 40 species, and there are only 6 species in existence, of the three species we are familiar with, the Australian lungfish is the rarest and most special, it is a genus of its own, the latest research confirms that it is the originator of all land vertebrates (formerly known as coelacanth). Others, such as the South American lungfish, are also a genus of their own, while the Victorian lungfish is the most beautiful. They have also been shown to have cartilage in their bones. Nature is really magical.
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