Alternative Name
Scientific Name: Colossoma brachypomus (silver) or colossoma macropomum (red-bellied)
Basic Info
These are tall fish which give the appearance of a Red-bellied Piranha (Pygocentrus nattereri but they tend to be somewhat plumper despite the fact that the two are often confused. The most significant morphological difference between the two is the the level of protrusion of the jaw (much smaller in pacus than in piranhas). This helps to illustrate the largely vegetarian nature of the pacu and the largely carnivorous nature of the piranha. They are either grey or silvery fish with red bellies and the pacu has red lower body fins as well. The tambaqui also grows to a size which Pygo. nattereri can never hope to achieve. The genus to which the tambaqui formerly belonged, Colossoma was, at the time, the only genus of fish in which true molars are present. All genera which sprang from Colossoma are now among that still-somewhat-small assortment. Though they aren't to be feared as much as piranhas, tambaquis have formidable teeth which will be used on careless keepers that anger or scare them. The name Serrasalmidae means "Salmons with a Saw" (David Schleser, "Piranhas: A Complete Owners' Manual"), and this accurately describes the dentition of the Pacus.
