The name piranha may come from a hybrid language composed of
Tupi-Guarani languages; it may be a compound word made of the
components 'pirá', meaning 'fish', and 'sanha' or 'ranha',
meaning 'tooth'. In Tupi, inalienably possessed nouns take the
prefix 't-', 's-', or 'r-' depending on the possessor, or zero
in combination; thus 'pirá'+'anha'. Alternatively, it may come
from Tupi 'pirá' ('fish') and 'ánha' (devil).
Piranhas belong to the subfamily of Serrasalminae (which also includes closely related herbivorous fish including pacus and silver dollars). Traditionally, only the four genera Pristobrycon, Pygocentrus, Pygopristis, and Serrasalmus are considered to be true piranhas, due to their specialized teeth. However, a recent analysis showed that, if the piranha group is to be monophyletic, it should be restricted to Serrasalmus, Pygocentrus, and part of Pristobrycon, or expanded to include these taxa plus Pygopristis, Catoprion, and Pristobrycon striolatus. Pygopristis was found to be more closely related to Catoprion than the other three piranha genera.
The number of piranha species is not known, and new species continue to be described. In 1988, it was stated that fewer than half of the approximately 60 nominal species of piranhas at the time were valid. More recently in 2003, one author recognized a total of 38 or 39 species, although the validity of some taxa remains questionable.
Piranhas are found only in the Amazon basin, in the Orinoco, in
rivers of the Guyanas, in the Paraguay-Paraná, and in the São
Francisco River systems; some species of piranha have extremely
broad geographic ranges, occurring in more than one of the major
basins mentioned above, whereas others appear to have much more
limited distributions. However, piranha (inevitably former
aquarium-dwellers) have been introduced into parts of the United
States, even being occasionally found in the Potomac River, but
they typically do not survive the cold winters of that region.
Recently a piranha was caught by a fisherman in the Catawba
River in North Carolina. This is the first known case in North
Carolina and possibly in the region.
They are normally about 15 to 25 cm long (6 to 10 inches), although reportedly individuals have been found up to 41 cm (24 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 that makes the individual teeth appear markedly triangular. The exception is Pygopristis, which has pentacuspid teeth and a middle cusp that is 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.
Ecologically, piranhas are important components of their native environments. Although largely restricted to lowland drainages, these fishes are widespread and inhabit diverse habitats within both lotic and lentic environments. Some piranha species are abundant locally and multiple species often occur together. As both predators and scavengers, piranhas influence the local distribution and composition of fish assemblages. Certain piranha species consume large quantities of seeds, but unlike the related Colossoma and Piaractus, herbivorous piranhas thoroughly masticate and destroy all seeds eaten and consequently do not function as dispersers.
The piranha is portrayed and known as a vicious species of fish hunting in large schools. This conception was created from the past belief that piranhas created schools for hunting purposes. Recent research, however, suggests that this is actually used as a defense mechanism against the piranha's natural predators, such as river dolphins, caimans and giant pirarucu.
Recent on Serrasalmus aff. brandtii and Pygocentrus nattereri in Viana Lake, which is formed during the wet season when the Rio Pindare (a tributary of the Rio Mearim) floods, has shown that these species eat vegetable matter at some stages in their life; they are not strictly carnivorous fish.
This Piranha Page is Copyright The Animal Web Guide © 2004 - 2009 Chuck Ayoub