In 1836, European scientists discovered an unusual animal in the Amazon River, which they hardly managed to identify. The body of the unknown species was depressed and reached a length of about 60 centimeters, and the lungs filled with air convinced the scientists that it must be a reptile, writes Science Focus.
A year later, another copy was found in Africa. Scientists studied the structure of his heart and declared it amphibians. Only after 30 years of disputes, scientific consensus was still achieved: the main hypothesis is that these are fish, but they differ from others. Instead of breathing water through the gills, they have light.
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The researchers found if the fish do not have access to the surface of the water to inhale the air, the West African Double -Propagent Fish (Protopterus Annectens) will drown. The fact is that the withered gills of this species are too small to provide a sufficient amount of oxygen, but bicnom -sucking fish have another unusual ability that helps them survive in a natural habitat - seasonally drying swamps and rivers.
Double -grooming fish gnaw off the holes in silt and build a kind of chamber filled with mucus, in which they turn off at rest, without eating and not moving - it continues until the rains return. It is known that in the wild this can last 7 or 8 months, at the same time, double -legged fish sleep for four years.
Scientists have already found out that double -sucking fish first appeared more than 400 million years ago. However, despite the age of the species, this species is still fraught with an incredible number of puzzles. For example, scientists have not yet been sufficiently investigated the connection between light and a feature of fish: the swimming bladder, which most fish use to swim underwater, and also hear and make sounds.
Note that this is not the only type of fish who have light ones - they were also found in multi -frying and smooth fish, but not one of them had light and swimming bladder. One organ may be the version of the other, but which one appeared the first? This question is still difficult to answer.
It is known that in fish embryos, a swimming bubble and lungs develop from a pocket in the intestines. Scientists have scanning both organs and found that both of them are associated with the circulatory system, but they are easy organ. The results also hint that swimming bubbles appeared later and, in fact, are modified light.
Another question that has long puzzled scientists is whether the bicom -moistened fish are the closest living relatives of all terrestrial four -legged animals, that is, all mammals, birds, reptiles and amphibians.
Recent studies suggest that this.
Scientists believe that double -legged fish are more distantly connected with bone fish, such as tuna and herring than with terrestrial vertebrates, including people. Six species of double -legged fish are currently known, including four from Africa. The female of the Australian double -legged fish, known as Mafusail, wears the title of the oldest fish living in captivity.
Previously, Focus wrote that the popular aquarium fish turned out to be a completely new look.