Temporal range: Miocene–Recent
|A red-bellied piranha at the Newport Aquarium|
A piranha or piraña (//, //, or //; Portuguese: [piˈɾɐ̃ɲɐ], Spanish: [piˈɾaɲa]), a member of family Serrasalmidae, or a member of the subfamily Serrasalminae within the tetra family, Characidae in order Characiformes, is a freshwater fish that inhabits South American rivers, floodplains, lakes and reservoirs. Although often described as extremely predatory and mainly feeding on fish, their dietary habits vary extensively, and they will also take plant material, leading to their classification as omnivorous.
Taxonomy and evolution
Piranhas belong to the subfamily Serrasalminae, which includes closely related omnivorous fish such as pacus. 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, 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 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.
Piranhas are indigenous to the Amazon basin, in the Orinoco, in rivers of the Guianas, in the Paraguay–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 3 were present in Paraguay–Paraná and 2 in São Francisco. Most species are restricted to a single river system, but some (such as the red-bellied piranha) occur in several. Many species can occur together; for example, seven are found in Caño Maporal, a stream in Venezuela.
Aquarium piranhas have been unsuccessfully introduced into parts of the United States. In many cases, however, reported captures of piranhas are misidentifications of pacu (e.g., red-bellied pacu Piaractus brachypomus is frequently misidentified as red-bellied piranha Pygocentrus nattereri). 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.
Depending on the exact species, most piranhas grow to between 12 and 35 cm (5–14 in) long. A few can grow larger, with the largest living species, the red-bellied, reaching up to 50 cm (20 in). There are claims of São Francisco piranhas at up to 60 cm (24 in), but the largest confirmed specimens are considerably smaller. The extinct Megapiranha which lived 8–10 million years ago reached about 71 cm (28 in) long, and possibly even 100 cm (40 in).
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.
Piranhas have one of the strongest bites found in bony fishes. Relative to body mass, the black piranha (Serrasalmus rhombeus) 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.
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 cormorants, caimans, and dolphins. Piranhas are "basically like regular fish with large teeth". A few other species may also occur in large groups, while the remaining are solitary or found in small groups.
Although generally described as highly predatory and primarily feeding on fish, piranha diets vary extensively, leading to their classification as omnivorous. In addition to fish (occasionally even their own species), documented food items for piranhas include other vertebrates (mammals, birds, reptiles), invertebrates (insects, crustaceans), fruits, seeds, leaves and detritus. 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. 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 masticated seeds and in most of these this was the dominant item. Piranhas will often scavenge, and some species such as Serrasalmus elongatus are specialized scale-eaters, feeding primarily on scales and fins of other fish. Scale- and fin-eating is more widespread among juvenile and sub-adult piranhas.
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 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. They are often considered a nuisance by fishers since 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 destroyed to prevent proliferation in the latter.
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.
Although often described as extremely dangerous in the media, piranhas typically do not represent a serious risk to humans. However, attacks have occurred, especially when the piranhas are in a stressed situation, such as the dense groups that may occur when the water is lower during the dry season and food is relatively scarce. Swimming near fishermen may increase the risk of attacks due to the commotion caused by struggling fish and the presence of bait in the water. 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 warning signs at high-risk locations, and beaches in such areas are sometimes protected by a barrier.
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 damming of the Tocantins River. In the state of São Paulo, a series of attacks in 2009 in the Tietê River resulted in 15 people with minor injuries. In 2011, another series of attacks at José de Freitas in the Brazilian state of Piauí resulted in 100 people being treated for bites to their toes or heels. On 25 December 2013, more than 70 bathers were attacked at Rosario in Argentina, causing injuries to their hands or feet. In 2011, a drunk 18-year-old man was attacked and killed in Rosario del Yata, Bolivia. In 2012, a five-year-old Brazilian girl was attacked and killed by a shoal of P. nattereri. In February 2015, a six-year-old girl died after being attacked by piranhas when her grandmother's boat capsized during a vacation in Brazil.
A common falsehood is that they can be attracted by blood and are exclusively carnivores. A Brazilian legend called "piranha cattle" states that they sweep the rivers at high speed and attack the first of the cattle entering the water allowing the rest of the group to traverse the river. These legends were dismissed through research by Hélder Queiroz and Anne Magurran and published in Biology Letters.
When former American 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.
- Freeman, Barbie; Nico, Leo G.; Osentoski, Matthew; Jelks, Howard L.; Collins, Timothy M. (2007). "Molecular systematics of Serrasalmidae: Deciphering the identities of piranha species and unraveling their evolutionary histories" (PDF). Zootaxa. 1484: 2. doi:10.11646/zootaxa.1484.1.1. Retrieved 25 June 2009.
- Froese, Rainer, and Daniel Pauly, eds. (2006). "Characidae" in FishBase. April 2006 version.
- Goulding, M (1980). The Fishes and the Forest: Explorations in Amazonian Natural History. University of California Press. pp. 153–170. ISBN 978-0-520-04131-8.
- BBC News Online (2 July 2007). "Piranha 'less deadly than feared'". Retrieved 2 July 2007.
- 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.
- Freeman, Barbie; Nico, Leo G.; Osentoski, Matthew; Jelks, Howard L.; Collins, Timothy M. (2007). "Molecular systematics of Serrasalmidae: Deciphering the identities of piranha species and unraveling their evolutionary histories" (PDF). Zootaxa. 1484 (4): 1–38. doi:10.1046/j.1439-0469.2000.384132.x. Retrieved 22 June 2009.
- Fahrenthold, David A. (29 May 2005) In River of Many Aliens, Snakehead Looms as Threat, The Washington Post.
- Nico, L., Fuller, P. and Neilson, M. Piaractus brachypomus. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. Revision Date: 23 August 2013
- "City cancels piranha bounty as other fish slaughtered". CNN.com Blogs. 13 July 2012.
- Froese, Rainer and Pauly, Daniel, eds. (2018). Species of Pygocentrus in FishBase. March 2018 version.
- Froese, Rainer and Pauly, Daniel, eds. (2018). Species of Serrasalmus in FishBase. March 2018 version.
- "Pygocentrus piraya". piranha-info.com. Retrieved 25 March 2018.
- Grubich, J.R.; Huskey, S.; Crofts, S.; Orti, G.; Porto, J. (2012). "Mega-Bites: Extreme jaw forces of living and extinct piranhas (Serrasalmidae)". Scientific Reports. 2: 1009. Bibcode:2012NatSR...2E1009G. doi:10.1038/srep01009. PMC 3526859. PMID 23259047.
- "Megapiranha". Prehistoric Wildlife. Retrieved 25 March 2018.
- Grubich, Justin R.; Huskey, Steve; Crofts, Stephanie; Orti, Guillermo; Porto, Jorge (20 December 2012). "Mega-Bites: Extreme jaw forces of living and extinct piranhas (Serrasalmidae)". Scientific Reports. 2: 1009. Bibcode:2012NatSR...2E1009G. doi:10.1038/srep01009. PMC 3526859. PMID 23259047.
- Red-Bellied Piranha Is Really Yellow New York Times (24 May 2003).
- Nico, L.G.; and D.C. Taphorn (1988). "Food Habits of Piranhas in the Low Llanos of Venezuela". Biotropica. 20 (4): 311–321. doi:10.2307/2388321. JSTOR 2388321.CS1 maint: uses authors parameter (link)
- Piorski, Nivaldo Magalhães; Alves, José de Ribamar Lima; Machado, Monica Rejany Barros; Correia, Maria Marlucia Ferreira (2005). "Alimentação e ecomorfologia de duas espécies de piranhas (Characiformes: Characidae) do lago de Viana, estado do Maranhão, Brasil". Acta Amazonica (in Portuguese). 35: 63. doi:10.1590/S0044-59672005000100010. Lay summary
- Petrovický, Ivan (1989). Aquarium Fish of the World A Comprehensive Illustrative Guide to Over 500 Aquarium Fish. New York City: Arch Cape Press. p. 92. ISBN 9780517679036.
- Onofrio-Grimm, O. (1993). Dictionary of Indian Tribes of the Americas. 1 (2 ed.). pp. 209–210. ISBN 978-0-937862-28-5.
- Weatherford, J.M. (1985). Tribes on the Hill. p. 28. ISBN 978-0-89789-071-7.
- Méthraux, A. (1948). "Tribes of Eastern Bolivia and the Madeira Headwaters". In Steward, J.H. (ed.). Handbook of South American Indians. 3. pp. 389, 402, 452.
- Geiger, Diana Pirahna as Pets – Exotic Pets. bellaonline.com
- 5 arrested for selling piranhas in Philippines. Agence France-Presse. 12 March 2011
- van der Sleen, P.; and J.S. Albert, eds. (2017). Field Guide to the Fishes of the Amazon, Orinoco, and Guianas. Princeton University Press. pp. 172–193. ISBN 978-0691170749.CS1 maint: uses editors parameter (link)
- Mol, Jan H. (2006). "Attacks on humans by the piranha Serrasalmus rhombeus in Suriname". Studies on Neotropical Fauna and Environment. 41 (3): 189–195. doi:10.1080/01650520600630683.
- Mintz, Zoe (26 December 2013) Piranha Attack In Argentina Injures More Than 70, Fish Tore 'Bits Of Flesh' Off Swimmers On Christmas. ibtimes.com
- "Ataque de piranhas deixa 15 feridos em 'prainha' no Rio Tietê". globo.com. 5 October 2009.
- Martins, Kelly (16 November 2011). "Praia no Rio Paraguai tem quase um ataque de piranhas por dia em MT". globo.com.
- "Net to take bite out of Brazilian piranhas". heraldsun.com.au. 10 July 2007.
- "Palmas registra 190 ataques de piranhas desde janeiro". globo.com. 16 July 2007.
- "Balneário no Piauí recebe 100 mil peixes para conter ataque de piranhas". br.noticias.yahoo.com. 12 September 2011.
- "Homem bêbado morre após ser atacado por piranhas na Bolívia". terra.com.br. 7 December 2011.
- "Menina é atacada por piranhas e morre no Amazonas". tvuol.uol.com.br. 25 October 2012.
- "Six-year-old girl dies after being eaten by PIRANHAS". Mail Online. 3 February 2015.
- "Piranhas vermelhas são medrosas e comem vegetais". EcoTerra Brasil. 2004. Archived from the original on 16 January 2011.
- "Experimentos provam que peixes se agrupam para defesa, não para ataque". Ciência Hoje. 9 May 2005. Archived from the original on 6 September 2008.
- Gonçalves, Alfredo J. (10 July 2007). "Boi de Piranha". Archived from the original on 8 January 2014.
- Queiroz, Helder; Magurran, Anne E (2005). "Safety in numbers? Shoaling behaviour of the Amazonian red-bellied piranha". Biology Letters. 1 (2): 155–7. doi:10.1098/rsbl.2004.0267. PMC 1626212. PMID 17148153.
- Layton, Julia (30 June 2008). "Can piranhas really strip a cow to the bone in under a minute?". HowStuffWorks. Retrieved 22 May 2009.
- Howard, Brian Clark, Brian Clark Howard (31 October 2011). "13 Scariest Freshwater Fish: Piranha". National Geographic. Retrieved 4 October 2012.
- Robinson, Joe (22 November 2005). "Rumble in the jungle with Amazon's killer piranha". Los Angeles Times. Retrieved 1 August 2009.
|Wikimedia Commons has media related to Serrasalminae.|
- Piranha at Curlie
- Eric J. Lyman: "Piranha meat could take a bite out of what ails you", Houston Chronicle, 17 July 1998
- How to maintain healthy piranha in the home aquarium
- "Piranha Feeding Frenzy", National Geographic.com (2015-03-19)