The red-bellied piranha or red piranha (Pygocentrus nattereri) is a species of piranhanative to South America, found in the Amazon River Basin, coastal rivers of northeasternBrazil, and the basins of the Paraguay and Paraná. The red-bellied piranha has a popular reputation as a ferocious predator, despite being primarily scavengers. As their name suggests, red-bellied piranhas have a reddish tinge to the belly when fully grown, although juveniles are a silver colour with darker spots. They grow to a maximum length of 33 centimetres (13 in) and a weight of 3.5 kilograms (7.7 lb). The way to distinguish males from females is that the female has a slightly deeper color of red on her belly.

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Pygocentrus nattereri is found in South America. Pygocentrus nattereri can be found east of the Andes in the Parana-Paraguay and Amazon basin. They can also be found in rivers of northeast Brazil and the Guianas.

Biogeographic Regions: neotropical (Native )

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Exotic

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Reported but unconfirmed

Type of Residency: Year-round

Global Range: Native to South America. Reported from 10 states, including Florida, Hawaii, Massachusetts, Michigan, Minnesota, Ohio, Oklahoma, Pennsylvania, Texas, and Virginia (Fuller et al. 1999).

Pygocentrus nattereri physical characteristics vary with location, population, and age. In juvenile P. nattereri there are differences in physical characteristics depending on the size of the fish. A change in color pattern does seem to develop as size increases. The thickening body tissue tends to cause the black internal line of the anal fin to disappear and both the number of body spots and the density of melanophores increases with growth. Adult specimens also tend to vary in color pattern and body size with geographic location. Generally P. nattereri is reddish-orange ventrally and silver-gray dorsally. The fins vary in color as well, with a black dorsal fin, black anal fin, and reddish-orange pectoral fins. The lateral color of the fish is a gray to silver- gray.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry

Pygocentrus nattereri is typically found in whitewater streams in South America (Saint-Paul 2000). However, the species is not found typically in blackwater streams (Fink 1993)

Habitat Regions: tropical ; freshwater

Aquatic Biomes: rivers and streams

Habitat Type: Freshwater

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Foraging methods vary in different life stages of P. nattereri. During the day, smaller fish (80-110 mm) search for food. At dawn, late afternoon, and early evening the larger fish (150-240 mm) search for food. Pygocentrus nattereri groups gather in vegetation in order to wait for prey. The group typically includes around 20-30 fishes. In the daytime P. nattereri can be seen lurking or ambushing prey. Two other methods for obtaining food employed by P. nattereri are chasing and scavenging. The hunting mode of chasing was seen after the fish lie and wait in vegetation. The fish then proceed to swim after and eat the fish. P. nattereri has a wide variety of food in its diet, including fins, scales, fish (pieces and whole), insects, snails, and plants. The plant intake of the animal may be an active way of gaining food supplies while scanning for prey.

Animal Foods: fish; carrion ; insects; mollusks

Plant Foods: leaves; fruit

Primary Diet: omnivore

An interesting relationship between P. nattereri and Serrasalmus marginatus has developed. Serrasalmus marginatus has been seen taking crustacean parasites off the bodies of P. nattereri.

Mutualist Species:

• Serrasalmus marginatus

Pygocentrus nattereri seems to have a type of courtship display that involves swimming in circles. This results in ventral-to-ventral interactions among the male and female. Eggs are placed in the sediment, in bowl shaped nests. These nests are around 4-5 cm in depth and 15 cm in diameter. The eggs are in clusters and are attached to the bottom vegetation. There may also be a relationship between the times of the spawning and the time of the wet season.

Breeding season: Spawning seems to occur during the wet season.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous

Pygocentrus nattereri has been introduced to the freshwaters of the United States on numerous occasions. Introductions have been reported in Florida, Hawaii, Massachusetts, Michigan, Minnesota, Ohio, Oklahoma, Pennsylvania, Texas, and Virginia. The fishes were probably releases from aquariums. When a piranha is found in a lake, many state agencies use the chemical rotenone to kill the fishes.

US Federal List: no special status

CITES: no special status

United States

Rounded National Status Rank: NNA - Not Applicable

Rounded Global Status Rank: GNR - Not Yet Ranked

Pygocentrus nattereri is considered one of the more dangerous and aggressive species of piranha.

Negative Impacts: injures humans (bites or stings)

Pygocentrus nattereri is one of the most commonly used piranhas in the aquarium trade.

Positive Impacts: pet trade

Comments: Formerly known as Serrasalmus nattereri (red-bellied piranha); referred to as Pygocentrus nattereri (red piranha) in 1991 AFS list (Robins et al. 1991).