Found in rivers and lakes across South America, piranhas are fish known for their sharklike feeding frenzies. Red-bellied piranhas are the most ferocious and the species most responsible for giving the fish its fearsome reputation. When prey becomes scarce, these hungry piranhas turn on their brethren as a source of food. More recently, piranhas have been introduced to Hawaii and parts of Central and North America, according to Animal Corner.
According to Facts About, piranhas can grow up to 45 cm long, though some, such as the red piranha, usually grow no longer than 30 cm. Piranhas usually live for about 25 years and can weigh up to 3.49 kg. The fish may swim and feed in groups containing up to 1,000 individuals. Female piranhas lay 5,000 eggs, according to Wild Facts. Because male piranhas are so good at guarding the nest, about 90 percent of these survive.
Piranhas may be relatively small, but they have sharp teeth set in powerful jaws--so sharp that they can bite through a steel fishing hook. The ability of the top and bottom teeth to interlock allows the fish to rip and tear flesh. Despite their popular perception as ferocious man-eaters, there are no confirmed reports of piranha ever killing a human. However, says Animal Planet, they will scavenge on human carcases. Indigenous South Americans use piranha teeth for making weapons, according to Facts About.
According to Facts About, piranhas are the most ferocious freshwater fish in the world. Piranhas usually select victims smaller than themselves. These include insects, other fish and tiny crustaceans. Nevertheless, attacks on animals as large as a horse have been reported. Not all of the 30 to 40 species of piranha eat meat. Some, according to Animal Planet, eat large amounts of seeds. Despite its ferocity, some animals include piranha in their diet. These include dolphins, crocodiles and turtles.
Piranhas have a high-backed and stocky body typical of fish that live in slow-moving waters. Their heads are large and steeply profiled. Piranhas are able to detect blood in the water using the same sensory system as sharks. Piranhas have a dorsal fin, adipose fin, pectoral fin, anal fin and a tail fin. When moving at high speeds, all of these, apart from the tail fin, are folded close to the body to streamline them better.