Lungfish: Water and Special Mucus Form

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Southern Africa is home to a very primitive fish with extraordinary abilities. It’s the lungfish. And while it not only has gills like any other fish, it can also breathe air directly using a modified swim bladder that acts as a lung. When water levels are high, this isn’t so important. But the rains will eventually fail. The constant burning sun will dry up all the water. Fish are left flapping on the surface as the water disappears. Only the air-adopting lungfish is able to cope with these extreme conditions, but it’s still exposed to the heat and it’s still at risk from predators. So it relies on another even more extraordinary ability. It finds a new safer home- bury underground. Digging down by eating mud and pushing it out through its gills, to stop it drying out, the lungfish issues a special mucus form its skin covering itself in a thick layer that hardens to form a waterproof cocoon. Only a single hole is left for breathing. Bided into this mud sarcophagus, the lungfish slows its metabolism to one sixtieth of its original rate relying on its muscles and body fat as a source of food and water. It becomes just another piece of harden mud. And lungfish have even been known to end up as an accidental brick in a mud hut wall. But this isn’t the end for the lungfish. It can survive like this for an incredible four years. Eventually, it could end up poisoned by its own waste products. But in this case, the onset of the rain is the salvation. As the mud walls are washed away, the lungfish’s hard mucus lining is softened. It’s been four years since it last used its muscles and they’re very weak. But, as it breaks free of this mud cocoon, it still manages to drag itself toward the nearest source of water. It’s the ultimate survivor. Although it is under water now, it’ll soon be back in the mud repeating the whole process again and again as the annual rains come and go.
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