The red-bellied piranha (Pygocentrus nattereri). Photo credit: Emily Etherington.
A piranha is a freshwater fish, native to tropical parts South American rivers east of the Andes, known for its sharp teeth and voracious appetite for meat. Piranhas are a member of the family Characidae in the order Characiformes. About 30 species have been identified.
Piranhas are normally about 14 to 26 cm long (5.5 to 10.25 in), although some specimens have been reported to be up to 43 cm (17.0 in) long. All have a row of razor-sharp teeth capable of slicing through flesh like scissors; however, only a few species pose a threat to humans These include the red-bellied piranhas that inhabit the Amazon and Orinoco river systems.
Piranhas have only adequate sight, but have excellent hearing, being very sensitive to vibrations. They also have an acute sense of smell.