occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: Native to South America; part of a species complex that is widely distributed in lowland areas east of the Andes (Fuller et al. 1999). S. HUMERALIS was reported to be formerly established in Florida but now extirpated (Robins et al. 1991). However, the species actually was S. RHOMBEUS, not S. HUMERALIS (see Fuller et al. 1999). That locally established population was exterminated in 1977 (Fuller et al. 1999).
Habitat Type: Freshwater
Comments: Has been found in Florida in an isolated sinkhole pool, an abandoned swimming pool, and in a pond (Fuller et al. 1999). Apparently also riverine in native range.
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.
Life History and Behavior
Researchers measured the bite force of 15 wild black piranhas in the Amazon basin. They found that the force exerted was 320 Newtons, the strongest recorded for any living bony or cartilaginous fish. After adjusting for size, that is about three times the force of an American alligator (Alligator mississippiensis) and more than is estimated for Tyrannosaurus rex.
These findings allowed a conservative estimate of the bite force of an extinct Miocense relative, the giant Megapiranha paranensis: an astounding 1240-4749 Newtons.
The combination of massive muscles and specially-shaped jaws explains this bone-crushing force which allows these piranhas to be apex predators in the Amazon basin.
Molecular Biology and Genetics
Statistics of barcoding coverage: Serrasalmus aff. rhombeus
Public Records: 0
Specimens with Barcodes: 1
Species With Barcodes: 1
Statistics of barcoding coverage: Serrasalmus rhombeus
Public Records: 0
Specimens with Barcodes: 21
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNA - Not Applicable
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Relevance to Humans and Ecosystems
Comments: One of the more aggressive pianha species, but danger to human has been greatly exaggerated (Fuller et al. 1999).
Serrasalmus rhombeus (Redeye Piranha, and see below), is a fish of the piranha family Serrasalmidae found in South America in the Amazon and Orinoco river basins, the north and eastern Guiana Shield rivers, and northeastern Brazilian coastal rivers. Its length is up to 41.5 cm.
These piranhas live in very diverse habitats ranging from soft blackwater, to hard whitewater areas in the Amazon, and as such, are very tolerant of differing water chemistry.
This fish was long known and traded as Serrasalmus niger. It varies widely across its range and whether it really is a single species is still unknown, though in some cases, the fish in question are certainly mere morphs. Peruvian S. rhombeus are called jet black highbacks or Peruvian Black Piranhas. Brazilian Black Piranhas are actually greyish in color and some have diamond-shaped scales. Venezuelan S. rhombeus have the brightest red eyes and grey coloration.
Other names include Rhombeus Piranha, for its striking shape. Particularly light-colored populations are the White Piranhas of the aquarium trade, formerly believed to be the "true" S. rhombeus. A common local name is caribe ojo rojo; the species is also known as caribe amarillo, not to be confused with the other "yellow" piranhas S. gibbus and S. spilople.
In the aquarium
It is generally recommended to keep no more than one in captivity, as redeye piranhas generally do not tolerate tankmates, particularly when they are adults. In the wild, it is believed that they generally form loose shoals (or schools, but seem to join and leave different shoals at will). Their primary source of food at a juvenile size is the fins and scales of other fish. In captivity it is possible for them to reach a size of up to 35 cm (14 in). It is rare to see them at this size, however, as their growth rate is generally very slow. Specimens that are in the upper size ranges can command very steep prices (such as $500 for a 30 cm (12 in) fish). In the aquarium they should be fed a varied diet. Many people feed beefheart, and recipes for mixtures abound on the internet. Feeding live food is controversial.
Like all piranha, they have razor sharp teeth and powerful jaws and caution should be used when performing tank maintenance, particularly when they are of a mature age. They are much bolder and extremely aggressive at an older age. Juveniles are, on average, fairly timid. Individual animal temperament does, of course, vary.
As with any aggressive species, a close attention to water parameters (i.e. ammonia, nitrates) is important, as they are very messy eaters.
While these fish school in nature, all Serrasalmus species are best kept as solitary piranhas in the aquarium, and S. rhombeus is no exception. They should be kept alone. In the confines of an aquarium, aggression between individuals will result in injured or killed fish, until a solitary, dominant fish emerges.
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