As the saying goes, "melons are inseparable from seedlings, fish are inseparable from water", under normal circumstances, fish need to live in water, whether it is freshwater fish or marine fish, after a long time away from the water, they will pay their lives as a price.
In the long process of environmental changes on the earth, in order to better adapt to the new environment, some fish have gradually evolved their own unique survival skills, such as blackfish, catfish, mudskippers, climbing perch and other fish, they have mastered the secret of temporary non-death from the water.
In addition, there is a fish that lives in Africa, whenever Africa ushers in the dry season, they will burrow into the soil and lie down, and they can survive for 4 years in the case of extreme water shortage.
1. Understand the African continent
Africa is the abbreviation of "Afrika", as one of the seven continents of the world, but also one of the birthplaces of ancient humans and ancient civilizations in the world, there are the earliest written records in 4000 BC, Egypt in northern Africa is one of the birthplaces of world civilization.
At the same time, there are relevant archaeological materials to prove that the people of all ethnic groups in Africa have created and developed brilliant ancient civilizations very early, and in ancient times, when the homeland of Western colonialists was still in the stage of glacier consolidation, there was already a boiling life on the African continent.
From the geographical point of view, the African continent is located near the equator, its climate characteristics are characterized by high temperature, little rain, dry, known as the "tropical continent", Africa's annual average temperature of more than 20 °C in the area accounts for about 95% of the continent's area, more than half of which is hot all year round, and nearly half of the area has a hot warm season and a warm cool season.
Most parts of the continent have four distinct seasons, but the climate of the African continent is only rainy and dry, and each season lasts about half a year, the dry season is generally from April to October, and the rainy season is from October to April.
At the time of the dry season, the animals and plants on the African continent will attract a huge test, heat, lack of water, food shortage and other problems have led to the loss of life of a large number of animals and plants, in the smooth passage of the dry season to lead to the rainy season, the animals and plants on the African continent are like ushering in a new life, full of vitality and peace.
In order to adapt to the unique environment and climate of the African continent, many animals, plants, fish, etc. have evolved their own unique skills, among many fish, African lungfish can be regarded as very successful, because they will burrow into the soil before the arrival of the dry season, when other fish are suffering, they are very relaxed and comfortable, just wait until the rainy season comes, when there is water flowing in the riverbed again, they will drill out of the soil to continue to live and reproduce, so how do African lungfish do all this?
Lungfish hiding in the dirt
2, African lungfish: a fish that will drown, how to achieve "not to die from the water"
The reason why fish can not leave the water, the first reason is that the fish can not get oxygen directly from the air, and their skin can not help them effectively lock the water, when the fish body after a large amount of water volatilization, they will also lose their lives due to dehydration, the last point is also the most critical point, there is no fish can leave the water to eat, if you want to live on land for a long time, the above 3 key points are fish need to overcome.
Natural selection, survival of the fittest, lungfish in up to 400 million years of continuous evolution and evolution, which also makes them master the secret of "not dying from the water", in addition to being able to easily cope with the African dry season for up to half a year, in the case of conditions permitting, African lungfish can even survive in the soil for 3 to 5 years, but it is such a fish, but it is a fish that will be drowned.
lungfish
The vast majority of fish rely on the gills to "breathe", when they breathe in the water, they will open the mouth of the fish, so that the water flow into the oropharyngeal cavity, at this time the gill cover is closed, the water flows through the gills, and then complete the gas exchange, in addition, some fish have evolved many ways to assist breathing, the gill organs and skin are two of the more common, such as fighting fish, bearded catfish, snakeheads and climbing perch and other fish have such organs, which is also the mystery of their short-term survival from the water.
In addition, scientists have also found that the oropharyngeal mucosa of yellow eels and electric eels can help them obtain oxygen directly from the air, and the surface of their oropharyngeal mucosa is full of capillaries, even many papillae, and dense capillaries also make their effective breathing area very large.
In contrast, the respiratory system of African lungfish is more intelligent, because African lungfish not only has normal gills, but also has the same "lungs" as us humans, which also makes African lungfish can obtain oxygen directly from the water body, and also can directly obtain oxygen from the air, laying a solid foundation for it to "not die from the water".
Schematic diagram of lungfish deplaning
The fish maw of the lungfish has a special opening in the pharynx to communicate with the esophagus, and there are many small air sacs distributed inside the fish maw, which are densely packed with thin-walled blood vessels for blood gas exchange, and the working mode of this organ and the lungs of mammals belong to the homologous relationship, hence the name lungfish.
Floating lungfish
At present, the only three remaining lungfish in the world are: Australian lungfish, American lungfish and African lungfish, of which African lungfish and American lungfish due to the specialization of lung function, the original fish gills have been more seriously degraded, even if they live in the water normally, they still need to float to the surface of the water to obtain oxygen directly from the air, which also makes them a fish that will be drowned in the name.
According to relevant media reports, a family on the African continent took advantage of the dry season to dig up a piece of dirt near the river for the construction of a house, which is very common in the local area, but it has lived like this for more than 4 years, probably because of the waterproofing of the roof, when the rainy season came, the rainwater soaked into the mud block of the house, and the lungfish that originally hid in the mud took the opportunity to get a new life and fled back to the river, while the traces of the cave where it lived remained on the wall of the house.
Lungfish hiding in the dirt
3, lungfish defeated nature, but lost to a hoe
Through the observation of scientists, it has been found that African lungfish will rely on "memory" and according to the surrounding environment to judge the time of the dry season, and prepare for the drought season in advance.
African lungfish will use the body to dig a bottle-shaped cave on the riverbed, the entire cave depth is about 20 centimeters, showing a wide bottom and slender state, at this time the African lungfish is tightly coiled together in a U-shape, and the body secretes a large amount of mucus to keep itself moist, because there is a vent above the cave, even in the underground cave, the African lungfish can get enough oxygen to maintain life.
At the same time, the dormant African lungfish, their metabolic rate will be reduced to one-sixtyth of the normal period, and the original fat will survive, such an environment is enough to support them to survive for 3 to 5 years. African lungfish, which hide in their burrows during the dry season, are normally able to survive this difficult period until the rainy season brings them back to life.
The African lungfish, which have overcome nature, should have had a smooth human life from then on, but they have tragically lost to a hoe.
Schematic diagram of the dormant African lungfish
Africa, the first thing that comes to mind is poverty, backwardness, and material scarcity, but when we know enough about Africa, we will find that all this is just our misunderstanding, Africa was once the birthplace of human civilization, if there is no rich material foundation, how can we achieve all this?
Herodotus once described agriculture in Egypt:
They were more likely than any other people in the world, including other Egyptians, to obtain the fruits of the earth without much labor, because they did not have to do the work that others had to do to reap the harvest. The farmers there simply waited for the river to flood out on its own, flowed to the fields for irrigation, irrigated them and then returned to the riverbed, and then each one sprinkled the seeds on his own land, told the pigs to go up and step into the seeds, and then just waited for the harvest. They used pigs to thresh and then put the grain into the barn. — Herodotus, History of the Persian War
Ptolemy's map of the world (colored version): There are rivers in North Africa
It can be seen that the African continent is not as barren and backward as we think, in some areas suitable for human habitation, its material base is extremely rich, and it is this superior condition that makes the local residents do not need too fine farming, and even in some parts of the African continent, the local people still live a relatively primitive hunting life, the animals in the rainforest, the fish in the river, and the fruits and vegetables on the land are their food sources.
Even at the onset of the dry season, local residents still have a way to get enough food, and the only headache for them may be getting fresh water.
The African lungfish, which are hidden in the mud during the dry season, are one of the important food sources for the locals, and it is extremely easy to catch these African lungfish.
Locals will look for small holes in the dry dirt, followed by a poke with branches or straw poles, if they feel that there is a hollow mucus protection layer, then they will not hesitate to excavate, some people will use hoes, some people will even dig with their bare hands, it will not take too much time, a live African lungfish appeared in front of us.
Perhaps many friends living in the countryside, after the rice fields and ditches release water, will go to find the cave of the yellow eel, followed by bare hands or using tools such as hoes to dig them out and catch them, compared to catching African lungfish is simpler.
In order to adapt to the changing environment, African lungfish evolved the ability to "not die from the water", and they still have a long life, in 2017, in the Chicago Aquarium in the United States, a lungfish that survived for more than 90 years died of illness, which is also the longest known lungfish.
However, the African lungfish through the dormancy to fight against nature, but let humans pick up a big leak, after a long time of local residents in Africa to catch, the current African lungfish population has been a large degree of decline, even to the point of precariousness, if you continue to catch indiscriminately, perhaps one day, did not lose to nature of the African lungfish, will eventually lose to a hoe.
References: Into Africa, Wikipedia