Apiranha orpiraña (/pɪˈrɑːnjəˌ-ræn/, or/pɪˈrɑːnə/;Portuguese:[piˈɾɐ̃ɲɐ],Spanish:[piˈɾaɲa]) is any of a number of freshwaterfish species in thefamilySerrasalmidae,[1] or the subfamily Serrasalminae within the tetra family,Characidae[2] inorderCharaciformes. These fish inhabit 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,[3] leading to their classification asomnivorous.[4]
Piranha inVenezuela with its jaws held open to show its distinctive sharp teeth
Piranhas belong to thefamilySerrasalmidae, which includes closely related omnivorous[8] fish such aspacus.[9] Traditionally, only the fourgeneraPristobrycon,Pygocentrus,Pygopristis, andSerrasalmus are considered to be true piranhas, due to their specialized teeth. However, a recent analysis showed, if the piranha group is to bemonophyletic, it should be restricted toSerrasalmus,Pygocentrus, and part ofPristobrycon, or expanded to include these taxa plusPygopristis,Catoprion, andPristobrycon striolatus.Pygopristis was found to be more closely related toCatoprion than the other three piranha genera.[9]
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.[9]
Distribution
Piranhas are indigenous to theAmazon basin, in theOrinoco, in rivers of theGuianas, in theParaguay–Paraná, and theSão Francisco River systems, but there are major differences in thespecies 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.[9] 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.[9]
Aquarium piranhas have been unsuccessfullyintroduced into parts of theUnited States.[10] In many cases, however, reported captures of piranhas are misidentifications of pacu (e.g., red-bellied pacu orPiaractus brachypomus is frequently misidentified as red-bellied piranha orPygocentrus nattereri).[11] Piranhas have also been discovered in theKaptai Lake in southeastBangladesh. 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 theLijiang River inChina.[12]
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, thered-bellied, reaching up to 50 cm (20 in).[13][14] There are claims ofSão Francisco piranhas at up to 60 cm (24 in), but the largest confirmed specimens are considerably smaller.[15] The extinctMegapiranha which lived 8–10 million years ago reached about 71 cm (28 in) long,[16] and possibly even 128 cm (50 in).[17]
Morphology
Serrasalmus,Pristobrycon,Pygocentrus, andPygopristis are most easily recognized by their uniquedentition. All piranhas have a single row of sharp teeth in both jaws. The teeth are tightly packed and interlocking (via smallcusps) 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 isPygopristis, 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 (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.[18]
Ecology
Close-up of a piranha at Georgia Aquarium
Piranhas vary extensively in ecology and behavior depending on exact species.[3] 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 ascormorants,caimans, anddolphins. Piranhas are "basically like regular fish with large teeth".[19] A few other species may also occur in large groups, while the remaining are solitary or found in small groups.[3]
Although popularly described as highly predatory and primarilyfeeding on fish, piranha diets vary extensively,[3] leading to their classification asomnivorous.[4] In addition to fish (occasionally eventheir own species[20]), documented food items for piranhas include other vertebrates (mammals, birds, reptiles), invertebrates (insects, crustaceans), fruits, seeds, leaves anddetritus.[3] The diet often shifts with age and size.[20] Research on the speciesSerrasalmus aff.brandtii andPygocentrus nattereri in Viana Lake inMaranhão, which is formed during the wet season when thePindaré River (a tributary of theMearim River) floods, has shown that they primarily feed on fish, but also eat vegetable matter.[21] In another study of more than 250Serrasalmus rhombeus atJi-Paraná (Machado) River, 75% to 81% (depending on season) of the stomach content was fish, but about 10% was fruits or seeds.[3] In a few species such asSerrasalmus serrulatus, the dietary split may be more equal, but this is less certain as based on smaller samples: Among 24S. serrulatus from flooded forests of Ji-Paraná (Machado) River, there were several with fish remains in their stomachs, but half containedmasticated seeds and in most of these this was the dominant item.[3] Piranhas will oftenscavenge,[9] and some species such asSerrasalmus elongatus are specializedscale-eaters, feeding primarily on scales and fins of other fish.[3] Scale- and fin-eating is more widespread among juvenile and sub-adult piranhas.[20]
Piranhas lay their eggs in pits dug during the breeding season and swim around to protect them. Newly hatched young feed onzooplankton, and eventually move on to small fish once large enough.[22]
Relationship with humans
Fishing piranha on theUcayali RiverA piranha, lightly grilled, served as food in the Peruvian AmazonA souvenir piranha
Piranha teeth are often used as tools themselves (such as for carving wood or cutting hair) or to modify other tools (such as sharpening ofdarts). This practice has been documented among several South American tribes including theCamayura andShavante in Brazil and thePacahuara in Bolivia.[23][24][25]
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.[9]
Piranhas can be bought as pets in some areas, but they are illegal in many parts of the United States, and in thePhilippines, where importers face six months to four years in jail, and the piranhas are destroyed to prevent proliferation.[26][27]
The most common aquarium piranha isPygocentrus nattereri, thered-bellied piranha. Piranhas can be bought fully grown or as young, often no larger than a thumbnail. It is important to keepPygocentrus 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.[citation needed] 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.[3][28] 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.[3][29] Swimming near fishermen may increase the risk of attacks due to the commotion caused by struggling fish and the presence ofbait in the water.[30][31] Splashing attracts piranhas and for this reason children are more often attacked than adults.[29] Being in the water when already injured or otherwise incapacitated also increases the risk.[3] There are sometimeswarning signs at high-risk locations[32] and beaches in such areas are sometimes protected by a barrier.[33]
Most piranha attacks on humans only result in minor injuries, typically to thefeet or hands, but they are occasionally more serious and very rarely can be fatal.[29] Near the city ofPalmas 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 thedamming of theTocantins River.[33][34] In the state ofSão Paulo, a series of attacks in 2009 in theTietê River resulted in minor injuries to 15 people.[31] In 2011, another series of attacks atJosé de Freitas in the Brazilian state ofPiauí resulted in 100 people being treated for bites to their toes or heels.[35] On 25 December 2013, more than 70 bathers were attacked atRosario in Argentina, causing injuries to their hands or feet.[30] In 2011, a drunk 18-year-old man was attacked and killed in Rosario del Yata,Bolivia.[36] In 2012, a five-year-old Brazilian girl was attacked and killed by a shoal ofP. nattereri.[37] In January 2015, a six-year-old girl was found dead with signs of piranha bites on part of her body after her family canoe capsized during a vacation in Monte Alegre, Brazil.[38] Whereas fatal attacks on humans are rare, piranhas will readily feed on bodies of people that already have died, such as drowning victims.[39]
Reputation
Various stories exist about piranhas, such as how they can skeletonize ahuman body orcattle in seconds. These legends refer specifically to thered-bellied piranha.[40]
Piranha solution, a dangerous mixture ofsulfuric acid andhydrogen 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 byblood and are exclusivelycarnivores.[41] 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.[42] These legends were dismissed through research byHélder Queiroz and Anne Magurran and published inBiology Letters.[43]
Accounts from Theodore Roosevelt
When former US presidentTheodore Roosevelt visitedBrazil in 1913, he went on a hunting expedition through theAmazon 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.[44][45] Roosevelt later described piranhas as vicious creatures in his 1914 bookThrough the Brazilian Wilderness.[46]
^Nico, L., Fuller, P. and Neilson, M.Piaractus brachypomus. USGS Nonindigenous Aquatic Species Database, Gainesville, FL. Revision Date: 23 August 2013.
^Cione, Alberto Luis; Dahdul, Wasila M.; Lundberg, John G.; Machado-Allison, Antonio (12 June 2009). "Megapiranha paranensis, a new genus and species of Serrasalmidae (Characiformes, Teleostei) from the upper Miocene of Argentina".Journal of Vertebrate Paleontology.29 (2):350–358.Bibcode:2009JVPal..29..350C.doi:10.1671/039.029.0221.ISSN0272-4634.S2CID86046546.
^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.ISBN978-0-517-67903-6.
