When it comes to the Amazon River, the first thing that comes to mind is the piranha, so in the Amazon River Basin, is there a piranha that does not dare to provoke? There really is, and that's Arapaima.
<h1 class="pgc-h-arrow-right" data-track="12" > natural enemy of piranhas: arapaima</h1>
Arapaima is an ancient fish known as a living fossil that now lives mainly in the Amazon basin of South America and has no close relatives in the world.
As its name suggests, Arapaima is a large freshwater fish. Mature arapaima can exceed 2.5 m in length, weigh up to 100 kg, and reach a maximum length of 4.5 to 6 m.
It feeds mainly on small fish, but occasionally preys on snakes, turtles, frogs and insects, and even on small crocodiles, and piranhas are also one of their prey.
Piranhas are a general term for a group of fish found in the Amazon River in South America. It does not refer to a particular species of fish, but to a taxon, including nearly 30 species, belonging to the sawfish subfamily of the family Licarpus.
Piranhas have a highly developed sense of hearing and have sharp teeth. After biting the prey, he clenched it and tore the flesh off with the twist of his body. One bite can bite down 16 cubic centimeters of meat. They often attack in the form of swarm fights, and once they smell blood, they become even more frantic, until they turn their prey into white bones.
In the seasonal lake caused by the dry season, piranhas are the main predators, while the Brazilian arapaima has to get close to more than 30 species of piranhas. Interestingly, piranhas eat other fish, mammals, and birds, but they can't do it.
This is because they have a god-level suit, the Golden Bell Hood Iron Cloth Shirt. To survive, Arapaima evolved scales with microscopic armor structures with toughness of up to 6.4 MPa/m1/2. Specially designed to defend against piranha attacks. Scientists have found that each of their scales contains stacked spiral-like layers of proteins that rotate inward and outward, revealing a very rare micro-nano-scale spiral plywood structure that is called a natural "reactive armor." It can absorb the energy from the external applied load and can effectively resist the expansion and extension of the crack, once an external force is applied, this layer of external "reactive armor" will naturally make an extension reaction to offset the applied force from the outside.
This also allows them to face piranha bites and can absorb or repel the power of piranha bites, because the scales are large and hard, and the Amazonians even grind their scales into claw knives.
Marc Meyers, a materials science researcher at the University of California, San Diego, and colleagues once used the teeth of a red-bellied piranha to bite the scales of the Brazilian arapaima, and the piranha's teeth were broken, which shows how strong the arapaima is, and almost no other aquatic creature can easily cause them damage.
The layered structure of the arapaima scales could provide inspiration for the development of new armor materials, which are expected to be more deformable and more impact resistant in the future. The U.S. Air Force hopes to provide better defensive armor protection for U.S. soldiers and weapon systems such as aircraft by studying these unique fish scales.
The bionic research team led by Professor Yu Shuhong of the University of Science and Technology of China, inspired by the natural arapaima scale armor, successfully prepared a three-dimensional artificial structure material with a bionic spiral plywood structure for the first time, providing a feasible manufacturing method for the design and preparation of super "artificial armor" with natural shield skin fish scale structure.
Arapaima , which is slightly large in size , is very good at jumping , jumping even out of the water when threatened , and swimming very fast underwater.
Arapaima also have a strong attack power, they use their tails as weapons, their huge size coupled with bolt-like underwater speed, rampage is no one can stop, even on the shore, they can easily knock down adult males, and break bones to cause a lot of internal injuries.
This is also why they can not be afraid of piranha bites, and can even use piranhas as prey.
<h1 class="pgc-h-arrow-right" data-track="12" > arapaima also has weaknesses</h1>
Arapaima live in the world's most pristine tropical jungle waters, where oxygen levels decrease in slow-moving rivers due to extremely hot weather. In particular, the Amazon and other tropical climates are similar, with two seasons, dry and rainy, and when the dry season comes, the space of the river water not only becomes smaller, but also full of rotten organic matter, and the oxygen content is very low. How to breathe has become a problem for arapaima to ponder.
So they evolved huge air sacs, which are made up of tissue from the lobes of the lungs and can act as additional respirators. So they need to float to the surface of the water to inhale oxygen, if the arapaima does not float to the surface for 15 minutes to breathe the "oxygen cylinder", it will make themselves suffocate. When the river level drops, they will drill a hole in the muddy riverbed and climb into it, surviving the long dry season, waiting for the river level to rise again, much like lungfish.
This otherwise invincible skill became a bug after the arrival of humans, and the local people would use the time window of the arapaima to hunt and kill. Arapaima has enormous economic value. A tonguefish has an average of 70 kg of fish meat, and the meat is very delicious, without fish spines.
About a century ago, this huge fish was the main fishing target in the Amazon basin, and when the larger fish were exhausted, local fishermen began to use gillnet gear to catch smaller fish, and in the process, some small arapaima that were not yet juvenile were killed, further harming their populations.
A century ago, arapaima catches exceeded 1200 tonnes a year in just one port in Brazil's Port of Belém. In 2006, the total declared volume of the entire Amazon basin reached only 380 tons. It is estimated that the number of individuals in the wild Arapaima population today is between 50,000 and 100,000.
With the killing of indigenous peoples, 3 of all 5 species of arapaima have not been seen for decades. So.
<h1 class="pgc-h-arrow-right" data-track="12" > where the future holds for arapaima</h1>
It can prevent piranhas, and in the dangerous Amazon River, it still exists for hundreds of millions of years, but the arapaima has not escaped the iron pot of humans.
With the extinction of arapaima, some local communities have stricter fishing practices, specifying the minimum size of fish that can be caught and limiting the use of gillnet fishing methods. As a result of proper management, many previously overfished arapaima populations are beginning to recover.
Hopefully, one day in the future, the Arapaima population will recover, or we'll only be able to see them in museums.