TRUE PIRANHA

Valid as; Pygocentrus piraya

(Cuvier, 1819)

INTRODUCTION

Pygocentrus piraya is the largest of the 3 species of true piranha often reaching the impressive size of 20 U.S. inches, though smaller one’s are imported for aquarium use. Having kept my first P. piraya in 1976, few were imported during that time. Most were not distinguished from P. nattereri by dealers, though the body color flames were a clear indication of the species true identity. The hobby of piranha keeping itself for the home aquarist did not really begin until the early 1960's. Prior to that, few people even knew what a piranha was, much less the number of species available. Today, it is not uncommon to find them in pet stores that specialize in oddball fishes. The other two species of true piranha (P. cariba and P. nattereri) are much smaller in size. P. piraya has the least dark body pigment in the genus, because spotting is reduced and then lost relatively early in ontogeny. The small sample available for color pattern descriptions indicates that the bright yellow-orange pigment of living specimens covers more of the body than similar pigmentation in other species. However, as in the other species in the genus, one might expect ontogenetic stage and environmental variables such as water color to effect pigmentation.

The classification of this species has been covered under genus Pygocentrus (here). The species closely resembles Pygocentrus nattereri. The only external differences between the two species is piraya size, flank flames and the growth of a rayed adipose fin that seem to develop after the species attains approximately 9 inches total length or larger (*sub-adult). Few people are able to keep this species in captivity because of the large size it attains. Some hobbyists, who are keeping piraya as a pet, remark how much more the head of piraya differs from other piranhas in genus Pygocentrus. However, only slight differences actually exist between the 3 species of Pygocentrus. (Click here) for a web page that discusses piranha head shapes. * Sub-adult -- A developmental life stage when fish exhibit most but not all traits of an adult fish.

IN THE AQUARIUM

Potentially Dangerous To Humans - Cautionary statement for hobbyists: Some aquarists report keeping this fish as a group, however long term results are sketchy (infighting) often resulting in death. Recommend keeping as a solitary species when juvenile to sub-adult or when they are very large adults. Less infighting is reported as adults, but I wouldn't trust that opinion too far!  Large water changes are recommended for any species of piranha kept as a group. Water changes keep the aggression levels low. OPEFE has several articles regarding this and the fright response (here). Mixing this species with other members of Pygocentrus (cariba and nattereri) is also reported. While this type of aquarium is somewhat successful and probably esthetically pleasing to the eye, it is also unnatural. Unnatural because these 3 species are not found together in the wild. Again, I prefer to err in caution and suggest hobbyists not mix the 3 species, you still run the risk of something going wrong, thereby losing your fish or fishes through  predation. While some may argue their experience has shown them these fish can be kept together, it does not over rule the naturalness of these beasts....Cannibalism!

In keeping unpredictable species like Pygocentrus its better to err for life than death! Some hobbyists also place non-piranha fish with their P. piraya. While this practice is not recommended for the average aquarists, advanced aquarists have had minor success in keeping bottom dwellers and small characins that are below this piranha’s notice. But don’t trust that logic too far. The suggested aquarium size for a single P. piraya (12 inches total length or smaller) is 125 gallons minimum. Anything smaller for this species is not recommended. For multiple P. piraya larger aquariums are strongly suggested.

BREEDING P. piraya in the home aquarium

Hobbyists as of this writing have not accomplished breeding P. piraya. However, there are some hobbyists trying and the purpose of my writing information here is to help provide data that may be of some help. P. piraya as described above, is the largest species in genus Pygocentrus. While their breeding habits are similar to P. nattereri, there are some things that need to be done in order to have the best suitable breeding environment. Sexually mature fishes are those that are (female) approximately 28 cm SL (= 11.02 inches SL) and male, 18.0 cm SL (=7.087 inches SL). Be sure to add 1.5 inches to achieve TL (= Total Length) to those previous numbers. Breeding sizes in aquariums may be smaller. P-FURY members have an active program to breed this species, with one member reporting eggs being released, but unfertilized. Because they are a large species and prone to excessive aggressive behavior, it is my recommendation that an aquarium of at least 500 U.S. gallons be used to facilitate breeding. While it may be possible to accomplish this in much smaller aquariums, I believe the greater accomplishment would be with the larger tank as this would give P. piraya a much better chance to feel at home. Smaller aquariums could cause aggressive behavior problems and territorial disputes. Though this could also play out in larger aquariums, but less likely. Cannibalism is a norm for Pygocentrus species and this species is no different. So be watchful for any problems that might occur. Body damage from bites could lead the group to attack and eat the injured fish. Like other species of piranha and pirambeba, the fish darken during breeding condition. Tail slapping and also nest building has been observed (see Hartt, 1870 notes below). This behavior is also common amongst all the species. In the wild, the water fluctuates (covered below) and this causes the fat storage in the dorsum area to be used as needed depending on the season. This then triggers egg production. As I stated with P. cariba, the spawning will occur if the fish is ready and the conditions are right. Water changes alone will not accomplish this nor will re-creating a wet season or dry season. The main thing with water fluctuation is the abundance or lack of food. Knowing how much is a problem as each fish is different as are the needs.

Water chemistry (here) for the rio Sao Francisco (and depending where you are) is: Temp; 21 - 24 C, pH; 6 - 7.8, Hardness up to 25 dGH. What I would also suggest is lowering the pH from the higher figure to about 6.0 and doing 30% water changes  every three days, using pre-conditioned water that had been treated by adding a phosphoric acid at the rate of 5 milliliters per gallon. The reasoning behind this is because it is known that some hard to breed catfishes from this region were able to be achieve breeding behavior and clutches of eggs using this method after the 5th water change. While there is no guarantee this might help P. piraya spawn, one never knows until all venues are examined. Peat filtration should be used in all cases. What might be of interest to readers is the natural pH value of Rio Sao Francisco can range anywhere from 4.8 to 7.8 and the areas where some P. piraya are caught (rio das Velhas, a tributary of the rio Sao Francisco) pH can average 6.5 to 8.7! Many organisms cannot tolerate high levels of acidity, and even those who can, face the problems that their food sources (such as insects) cannot survive in highly acidic environments. As acidity in a water system increases, the number and diversity of organisms decreases. Also, at levels of pH 5, most fish eggs cannot hatch (see: Project Amazonas, Threats - Pollution). Getting back to breeding this species and its requirements, a biological filtration box (wet/dry system) should be used as majority of successful breeding of P. nattereri has been accomplished using this method. Add a couple air stones in each end of the tank. Lastly, go back and read information on S. maculatus and P. nattereri as the general rules for breeding would nearly apply here too. However, water quality and chemistry are two very important items to consider. According to Myers, 1972 in his account of Hartt (1870, p. 401) this scientist  gave some circumstantial information on the breeding of P. piraya. This information was given to him by Fishermen of the Rio Sao Francisco. "The fish clean out a shallow nest on the sandy bottom and spawn in it. The female guards the nest and viciously attacks any animal or human who comes near. This is said to take place principally in October soon after the rains raise the water level."

No record of P. piraya spawning in public aquariums has ever been reported. It has also been discovered that the following statement (italicized) below are inaccurate regarding spawning at a public aquarium. The species being discussed was P. nattereri not P. piraya. The inaccurate remarks will be left on line so that current readers may update themselves:

Schulte (1988) reported spawning have occurred at Aquarium Zoological Gardens in Frankfurt, Germany and Zoological Gardens, Hellabrunn, Munich, Germany, however, it was not determined that P. piraya was the species bred in captivity.

COLOR OF LIFE

Fink, W. L.  1993 (18 Aug.)  Revision of the piranha genus Pygocentrus (Teleostei, Characiformes). Copeia 1993

Sub-adults and Adults (color in preservative)

Based on specimens 130.9 mm SL and 143mm SL, ground color is pale goldish-brown, darker above, becoming  silvery-gold below the lateral midline. No spotting, and virtually no dark pigmentation, are present. The dorsal fin has some duskiness at fin base in some specimens; adipose fin with narrow dark border; anal fin with some dusky pigment, primarily in a narrow line along the distal border of the posterior two-thirds of the fin; fins otherwise hyaline. Dark vertical band passes through the eye, which is otherwise gold color.

Juveniles (color in preservative)

Juvenile color pattern, based on eight specimens 20-69 mm SL Bahia, Brazil (fig. 6 above), as in adults but more brownish background color. Posterior borders of the vertical fins are faintly dusky, with but a small amount of pigment. There are numerous round dark spots on the lateral body, including the belly region, but less numerous in the latter region.

This species has the least dark body pigment in the genus, because spotting is reduced and then lost relatively early in development. The small samples available for color pattern descriptions indicates that the bright yellow-orange pigment of living specimens covers more of the body than similar pigmentation in the other species. However, as in the other species in the genus, one might expect developmental stage and environmental variables such as water color to effect pigmentation. The eye color is yellowish-orange, with a dark black vertical stripe. Most of the lateral body is is bright yellow-orange, the color extends from the border of the head, up to the dorsal to the lateral line, extending to the rear of the caudal peduncle to the base of the ventral caudal-fin lobe. Pectoral, pelvic, and anal fins are bright yellow-orange. The anal fin has a narrow posterior black border. The dorsal, adipose, and caudal fins are dark as in the dorsal part of the body; there is a pale or hyaline area on the caudal fin between the proximal and distal black bands. 3 belly colors (red, orange, or yellow) are presumed to occur in P. piraya depending on locality and age.

Teeth

The teeth of Pygocentrus piraya are broad, serrated, tricuspid and razor sharp. These teeth are used for slicing chunks of fish. These teeth are backup by strong musculature that have enough force with combination of the teeth to clip off a finger or toe! A medium sized P. piraya (12 inch specimen) can have teeth as long as 10 mm TL or larger depending on the overall size of the animal.

Science

William L Fink - 1993

• Pygocentrus piranha, from the Rio São Francisco of Brazil, described by Aggassiz (in Spix and Agassiz, 1829); see Kottelat, 1988, regarding authorship of taxa described in this work) as a Serrasalmus. Long considered a synonym of piraya (Eigenmann, 1915; Norman, 1929). Type no longer extant.

• Pygocentrus piraya, described by Cuvier (1819) as a Serrasalmus. Type no longer extant. Considered Valid herein.

• Pygocentrus piraya (Cuvier, 1819)

• Pygocentrus dorsalis (Kner (ex Heckel), 1860)

• Pygocentrus piranha (Agassiz, 1829)

SEXUAL DIMORPHISM

(CROSS, A.M.G.; SATO, Y.; RIZZO, E.; SAINTS, G.B.; BAZZOLI, N. sexual Maturação of piranha Pygocentrus piraya (Cuvier, 1820) (Pisces, Characidae) in the dam of Three Marias, Minas Gerais. Bios , 4 (4): 17-22, 1996).

Sexual dimorphism has been reported for the species via microscopic examination of the gonads. These fish were later raised and sexuality determined by age, sexual maturity and size.

DISTRIBUTION

The species is restricted to the Rio Sáo Francisco drainage of Brazil where the populations are being diminished because of human intervention and expansion. This species and S. brandtii are the only piranhas known to inhabit this river and its tributaries.

REFERENCES  

• Spix, J. B. von and L. Agassiz   1829-31 Selecta genera et species piscium quos in itinere per Brasiliam annos MDCCCXVII-MDCCCXX jussu et auspiciis Maximiliani Josephi I.... colleget et pingendso curavit Dr J. B. de Spix.... Monachii. Selecta Piscium Brasiliam: Part 1: i-xvi + i-ii + 1-82, Pls. 1-48;, Part 2: 83-138, Pls. 49-101. [Part 1 published June 1829, part 2 Jan. 1831; see Kottelat 1988, Whitehead & Myers 1971, Pethiygoda & Kottelat 1998.]

• Fink, W. L.   1993 (18 Aug.)  Revision of the piranha genus Pygocentrus (Teleostei, Characiformes). Copeia 1993 (no. 3): 665-687.

• Kner, R.   1860  Zur Familie der Characinen. III. Folge. Der Ichthyologischen Beiträge. Denkschr. Akad. Wiss. Wien v. 18: 9-62, Pls. 1-8. [Also as a separate, pp. 1-54, with dual pagination. Some taxa appeared first in Kner 1858. Pygocentrus bidorsalis Kner (ex Heckel) 1860: 36 [28] [Denkschr. Akad. Wiss. Wien v. 18; . On p. 28 of separate. Not available, name mentioned in text under Pygocentrus piraya Müller and Troschel. Characidae: Serrasalminae. Habitat: freshwater.

• Cuvier, G.   1819  Sur les poissons du sous-genre Hydrocyon, sur deux nouvelles espèces de Chalceus, sur trois nouvelles espèces du Serrasalmes, et sur l'Argentina glossodonta de Forskahl, qui est l'Albula gonorhynchus de Bloch. Mem. Mus. Natl. Hist. Nat. v. 5: 351-379, Pls. 26-28.

• Bertin, L.   1948 Catalogue des types de poissons du Muséum national d'Histoire Naturelle. 3e partie. Ostariophysaires (Characiniformes, Gymnotiformes). Cat. Fish Types, Paris 3e partie: 1-49.

• Britski, H. A.   2001 Sobre a obra Velhas-Flodens Fiske [Peixes do Rio das Velhas]. In: Alves and Pompeu (organizers) Peixes do Rio das Vehlas: Passado e presente. Belo Horizonte, SEGRAC. cap. 1. Peixes do Rio das Velhas: 15-22.

• BLACKSMITH, R.M.A.; BAZZOLI, N.; RIZZO, E.; SATO, Y. - reproductive Aspects of piranha, Pygocentrus piraya (Teleostei, Characiformes), native species of the basin of the River Sâo Francisco. Arq. Bras. Med. Vet. Zootec. 48 (supl. 1): 71-76, 1996.

• CROSS, A.M.G.; SATO, Y.; RIZZO, E.; SAINTS, G.B.; BAZZOLI, N. sexual Maturação of piranha Pygocentrus piraya (Cuvier, 1820) (Pisces, Characidae) in the dam of Three Marias, Minas Gerais. Bios , 4 (4): 17-22, 1996.

• BAZZOLI, N.; RIZZO, E.; SAINTS, J. E.; SATO, Y. - Dynamic of ovogênese in forrageiros fish of the dam of Three Marias, Minas Gerais: histológico and histoquímico study. Bios, 4 (4): 5-10, 1996.

• Schute, Wolfgang - Piranhas in the Aquarium TFH Publications, Inc. NJ pg. 87-88, 1988.

• Hartt, Charles Frederick. 1870. "Geology and Physical Geography of Brazil." In: Thayer Expedition: Scientific Results of a Journey in Brazil, by Louis Agassiz and his travelling companions, Boston.

• Myers, G. S. 1972, The Piranha Book, M-539 TFH Publications, Inc. Neptune NJ.

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Created: April 10, 1994

UPDATED: 07/10/2009