and Monster Fish of the Congo
From Wikipedia, the free encyclopedia
A piranha or piraña (pronounced /pɨˈrɑːnə/, /-njə/ or /pɨˈrænə/, /-njə/; Portuguese: [piˈɾaɲɐ]) is a member of a family of omnivorous freshwater fish which live in South American rivers. InVenezuelan rivers, they are called caribes. They are known for their sharp teeth and a voracious appetite for meat.
Piranhas belong to the subfamily Serrasalminae, which also includes closely related herbivorous fish such as pacus. Traditionally, only the four genera Pristobrycon, Pygocentrus, Pygopristisand 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 Catopricornis than the other three piranha genera.
The total number of piranha species is unknown and new species continue to be described. In 1988, it was stated that fewer than a 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 in the Amazon basin, in the Orinoco, in rivers of the Guyanas, in the Paraguay-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.
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 Winnebago in Wisconsin, although they typically do not survive cold winters. Piranhas have also been discovered in the Kaptai Lake in south-east Bangladesh. More recently a dead Piranha was discovered in a river in Devon, England. 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 rogue exotic fish traders have released them in the lake to avoid being caught by anti-poaching forces.
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 thepremaxillary teeth are in two rows, as in most other serrasalmines.
Piranhas are important ecological components of their native environments. Although largely restricted to lowland drainages, these fish 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 entirely devour all seeds eaten and consequently do not function as dispersers.
Piranha have a reputation as a fearless fish who hunt their prey in ferocious packs. However, recent research, which “started off with the premise that they school as a means of cooperative hunting”, discovered that they were in fact rather fearful fish, like other fish, who schooled for protection from their predators, such as cormorants, caimans and dolphins. Piranhas are “basically like regular fish with large teeth”.
Research on the species Serrasalmus aff. brandtii and Pygocentrus nattereri in Viana Lake, which is formed during the wet season when theRio 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.
There are various myths about piranhas like they can dilacerate a human body or a cattle in seconds. Those myths refers specifically onPygocentrus 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.
The most common aquarium piranha is Pygocentrus nattereri, the red-bellied piranha. Piranhas can be bought fully grown or as babies, often no larger than a thumbnail. It is important to keep Pygocentruspiranhas alone or in groups of four or more, not in pairs, since aggression among them is common and is distributed more widely when kept in larger groups, not allowing the weaker fish to survive. It is not rare to find individuals with one eye missing due to a previous attack. If underfed, piranhas are likely to become cannibalistic on others in their group.