PIRANHA

Piranhas are found in the Amazon basin, in the Orinoco, in rivers of the Guyanas, in theParaguay-Paraná, and the São Francisco River systems. Some species of piranha have broad geographic ranges, occurring in more than one of the major basins mentioned above, whereas others appear to have more limited distributions.^[4]

Aquarium piranhas have been introduced into parts of the United States with specimens occasionally found in the Potomac River and even as far north as Lake of the Ozarks in Missouri and Lake Winnebago in Wisconsin, although they typically do not survive cold winters.^[5] Piranhas have also been discovered in the Kaptai Lake in south-east Bangladesh. Research is being carried out to establish how piranha have moved to such distant corners of the world from their original habitat. It is anticipated that some rogue exotic fish traders have released them in the lake to avoid being caught by anti-poaching forces.

Piranhas are normally about 14 to 26 cm long (6 to 10 inches), although some specimens have been reported to be up to 43 cm (18.0 inches) in length.^[7]

Serrasalmus, Pristobrycon, Pygocentrus and Pygopristis are most easily recognized by their unique dentition. All piranhas have a single row of sharp teeth in both jaws; the teeth are tightly packed and interlocking (via small cusps) and used for rapid puncture and shearing. Individual teeth are typically broadly triangular, pointed and blade-like (flat in profile). There is minor variation in the number of cusps; in most species, the teeth are tricuspid with a larger middle cusp which makes the individual teeth appear markedly triangular. The exception is Pygopristis, which has pentacuspid teeth and a middle cusp usually only slightly larger than the other cusps. In the scale-eating Catoprion, the shape of their teeth is markedly different and the premaxillary teeth are in two rows, as in most other serrasalmines.