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(piranhas, or caribes), a family of predacious fishes of the order Cypriniformes. The jaws are powerful, and the teeth are sharp. There are three genera, distributed in the freshwaters of South America. They prey in huge schools, tearing pieces of flesh from their victim’s body. They can completely clean a skeleton of a large animal, such as a capybara, in a moment. The fish are attracted by the smell of blood and by splashes in the water. Of the four large species especially dangerous to humans, the best known are Rooseveltiella nattereri, which reaches 30 cm in length, and Pygocentrus piraya, which reaches 60 cm. Piranhas lose their aggressiveness when kept in an aquarium.