Arapaima gigas is a big fish in a bigger river full of piranhas, but that doesn't mean it's an easy meal. The freshwater giant has evolved armor-like scales that can deform, but do not tear or crack, when a piranha -- which has one of the animal kingdom's most powerful bites -- attacks. Researchers from UC San Diego and UC Berkeley describe the unique properties of the Amazonian Arapaima skin and its potential for human-made materials October 16 in the journal Matter.