Description
Piranhas are normally about 15 to 25 cm long (6 to 10 inches), although some specimens have been reported to be up to 43 cm (18.0 inches) in length.
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.
Myths
There are various myths about piranhas like they can dilacerate a human body or a cattle in seconds. Those myths refers specifically on Pygocentrus nattereri, the red piranha. A very recurrent myth is they can be attracted by blood and are exclusive carnivores. In Brazil was created a myth called "piranha cattle" saying that they sweep the rivers at high speed and attack the first cattle as he enters the water allowing a group of cattles trepassing the river. Those myths were dismissed on research by Helder Queiroz and Anne Magurran and published on Biology Letters.
Relationship with humans
Piranha teeth are often used to make tools and weapons by the indigeneous population. Piranha are also popular as food, although if an individual piranha is caught on a hook or line, it may be attacked by other (free) piranhas.
Piranha are commonly consumed by subsistence fishermen and often sold for food in local markets. In recent decades, dried specimens have been marketed as tourist souvenirs. Piranhas occasionally bite and sometimes injure bathers and swimmers. A piranha bite is sometimes considered more an act of carelessness than that of misfortune, but piranhas are a considerable nuisance to commercial and sport fishers because they steal bait, mutilate catch, damage nets and other gear and may bite when handled.
Several piranha species appear in the aquarium trade. Piranhas can be bought as pets in some areas, but they are illegal in many parts of the United States including Alabama, Alaska, Arizona, Arkansas, California, Colorado, Florida, Georgia, Hawaii, Kentucky, Louisiana, Maine, Massachusetts, Mississippi, Nevada, New Mexico, New York, North Carolina, Oklahoma, South Carolina, Texas, Utah, Virginia and Washington.
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