Amazonian Fish Has Body Armor That Can Defeat Piranha Bites

Arapaima gigas has two layers of scales that are hardened and flexible, according to UC San Diego study.

The Amazon River region is home to a variety of creatures that have to deal with a range of predators, from jaguars and giant horned frogs, to the anaconda. One of the most storied predators on the Amazon is the piranha, a fish known worldwide for its razor sharp teeth and seemingly voracious appetite. There are stories of these little fish feasting on animals big and small in the river that it causes one to wonder if there is anything in the Amazon that is impervious to its bite. It appears that evolution has helped to armor one such species with scales so thick that even the piranha cannot penetrate its skin. That fish is called the arapaima (Arapaima gigas), a large freshwater species that grows to up to eight feet in length and has skin covered with two layers of scales designed to stop the bite of the piranha from doing any damage.

Marc Meyers, a University of California, San Diego materials science professor has been studying the arapaima’s scales and the effects a piranha tooth has on its strength. What his research staff found was the piranha tooth failed to puncture the scales of the fish, and often broke as it was pulled out. Meyers describes the scales as thick triangular ridges that are unique to the fish and are also flexible in that they can bend. The outer scales are comprised of mineralized bio-material while the inner scales are constructed of collagen fibers that form the flexibility of this suit of piranha proof armor. Materials created to mimic the scale’s strength could conceivably be used for military body armor, fuel cells, and other applications, according to a video released by the university.


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