A piranha (, or ; ) is any of a number of freshwater fish species in the subfamily Serrasalminae, of the family Serrasalmidae,[ leading to their classification as omnivorous.]
Etymology
The name originates from Tupi language ,
Taxonomy and evolution
Piranhas belong to the family Serrasalmidae, which includes closely related omnivorous[ Black-finned Pacu Fish, Colossoma macropomum Profile with care, maintenance requirements and breeding information for your tropical fish. Badmanstropicalfish.com. Retrieved on 13 May 2012.] fish such as .
Under more recent taxonomic treatments, essentially all members of the subfamily Serrasalmidae within the family Serrasalmidae have "piranha" in their name, excluding the most basal members of the subfamily, Metynnis, which are referred to as "silver dollars".
The total number of piranha species is unknown and contested, and new species continue to be described. Estimates range from fewer than 30 to more than 60.
Distribution
Piranhas are indigenous to the Amazon basin, in the Orinoco, in rivers of the Guianas, in the Paraguay River–Paraná, and the São Francisco River systems, but there are major differences in the species richness. In a review where 38–39 piranha species were recognized, 25 were from the Amazon and 16 from Orinoco, while only three were present in Paraguay–Paraná and two in São Francisco.
Aquarium piranhas have been unsuccessfully introduced into parts of the United States.[Fahrenthold, David A. (29 May 2005) "In River of Many Aliens, Snakehead Looms as Threat", The Washington Post.] In many cases, however, reported captures of piranhas are misidentifications of pacu (e.g., red-bellied pacu or Piaractus brachypomus is frequently misidentified as red-bellied piranha or Pygocentrus nattereri).[Nico, L., Fuller, P. and Neilson, M. Piaractus brachypomus. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. Revision Date: 23 August 2013.] Piranhas have also been discovered in the Kaptai Lake in southeast Bangladesh. Research is being carried out to establish how piranhas have moved to such distant corners of the world from their original habitat. Some rogue exotic fish traders are thought to have released them in the lake to avoid being caught by antipoaching forces. Piranhas were also spotted in the Lijiang River in China.
Description
Size
Depending on the exact species, most piranhas grow to between long. A few can grow larger, with the largest living species, the red-bellied, reaching up to .
Morphology
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 are used for rapid puncture and shearing. Individual teeth are typically broadly triangular, pointed, and blade-like (flat in profile). The variation in the number of cusps is minor. 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.
Biting abilities
Piranhas have one of the strongest bites found in bony fishes. Relative to body mass, the black piranha ( Redeye piranha) produces one of the most forceful bites measured in vertebrates. This extremely powerful and dangerous bite is generated by large jaw muscles (adductor mandibulae) that are attached closely to the tip of the jaw, conferring the piranha with a mechanical advantage that favors force production over bite speed. Strong jaws combined with finely serrated teeth make them adept at tearing flesh.
Ecology
Piranhas vary extensively in ecology and behavior depending on exact species.[ Piranhas, especially the red-bellied ( Pygocentrus nattereri), have a reputation as ferocious predators that hunt their prey in schools. Recent research, however, which "started off with the premise that they school as a means of cooperative hunting", discovered they are timid fish that schooled for protection from their own predators, such as , , and . Piranhas are "basically like regular fish with large teeth".][ Red-Bellied Piranha Is Really Yellow New York Times (24 May 2003).] A few other species may also occur in large groups, while the remaining are solitary or found in small groups.[
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Although popularly described as highly predatory and primarily Piscivore, piranha diets vary extensively,[ leading to their classification as omnivorous.][ In addition to fish (occasionally even their own species][ The diet often shifts with age and size.][ Research on the species Serrasalmus aff. brandtii and Pygocentrus nattereri in Viana Lake in Maranhão, which is formed during the wet season when the Pindaré River (a tributary of the Mearim River) floods, has shown that they primarily feed on fish, but also eat vegetable matter.][ Lay summary] In another study of more than 250 Serrasalmus rhombeus at Ji-Paraná (Machado) River, 75% to 81% (depending on season) of the stomach content was fish, but about 10% was fruits or seeds.[ In a few species such as Serrasalmus serrulatus, the dietary split may be more equal, but this is less certain as based on smaller samples: Among 24 S. serrulatus from flooded forests of Ji-Paraná (Machado) River, there were several with fish remains in their stomachs, but half contained Chewing seeds and in most of these this was the dominant item.][ Piranhas will often scavenge,][ Scale- and fin-eating is more widespread among juvenile and sub-adult piranhas.][
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Piranhas lay their eggs in pits dug during the breeding season and swim around to protect them. Newly hatched young feed on zooplankton, and eventually move on to small fish once large enough.
Relationship with humans
Piranha teeth are often used as tools themselves (such as for carving wood or cutting hair) or to modify other tools (such as sharpening of darts). This practice has been documented among several South American tribes including the Camayura and Shavante in Brazil and the Pacahuara in Bolivia.
Piranhas are also popular as food, being both eaten as a subsistence catch by fishers and sold at market. However, they are often considered a nuisance by fishers because they steal bait, eat catches, damage fishing gear, and may bite when accidentally caught.
Piranhas can be bought as pets in some areas, but they are illegal in many parts of the United States, and in the Philippines, where importers face six months to four years in jail, and the piranhas are destroyed to prevent proliferation.[Geiger, Diana Piranha as Pets – Exotic Pets. bellaonline.com][ 5 arrested for selling piranhas in Philippines . Agence France-Presse. 12 March 2011]
The most common aquarium piranha is Pygocentrus nattereri, the red-bellied piranha. Piranhas can be bought fully grown or as young, often no larger than a thumbnail. It is important to keep Pygocentrus piranhas alone or in groups of four or more, not in pairs, since aggression among them is common, not allowing the weaker fish to survive, and is distributed more widely when kept in larger groups. It is not uncommon to find individual piranhas with one eye missing due to a previous attack.
Attacks
Although often described as extremely dangerous in the media, piranhas typically do not represent a serious risk to humans.[ Splashing attracts piranhas and for this reason children are more often attacked than adults.][ Being in the water when already injured or otherwise incapacitated also increases the risk.][ There are sometimes at high-risk locations]
Most piranha attacks on humans only result in minor injuries, typically to the feet or hands, but they are occasionally more serious and very rarely can be fatal.[ Near the city of Palmas in Brazil, 190 piranha attacks, all involving single bites to the feet, were reported in the first half of 2007 in an artificial lake which appeared after the of the Tocantins River.][Mintz, Zoe (26 December 2013) Piranha Attack In Argentina Injures More Than 70, Fish Tore 'Bits Of Flesh' Off Swimmers On Christmas. ibtimes.com] In 2011, a drunk 18-year-old man was attacked and killed in Rosario del Yata, Bolivia.
Reputation
Various stories exist about piranhas, such as how they can skeletonize a human body or cattle in seconds. These legends refer specifically to the red-bellied piranha.
Piranha solution, a dangerous mixture of sulfuric acid and hydrogen peroxide known to aggressively dissolve organic material, draws its name from these legends surrounding the piranha fish.
A common falsehood is that they can be attracted by blood and are exclusively .
Accounts from Theodore Roosevelt
When former US president Theodore Roosevelt visited Brazil in 1913, he went on a hunting expedition through the Amazon Rainforest. While standing on the bank of the Amazon River, he witnessed a spectacle created by local fishermen. After blocking off part of the river and starving the piranhas for several days, they pushed a cow into the water, where it was quickly torn apart and skeletonized by a school of hungry piranhas.
See also
External links
