Serrasalmidae is a family of fishes of the suborder Characoidei. The body is compressed from the sides, covered with scales. The jaws have teeth. Includes 3 genera, about 15 species. Body length 25-60 cm. Inhabit fresh waters of South America. Gregarious, predatory fish. Fisheries are not important. Few serrasalmidae - objects of aquarium fish breeding.
Serrasalmidae reach a total length of up to 108 cm and a mass of up to 40 kg.
The structure of the lower jaw and teeth allows it to tear large pieces of meat from its prey. The teeth have the form of a triangle 4-5 mm high and are arranged in such a way that the teeth of the upper jaw evenly enter the grooves between the teeth of the lower jaw. Jaws act in two ways: when closing the jaws meat is cut off as a razor sharp teeth, when shifting closed jaws in a horizontal direction fish can bite off more dense tissues - veins and even bones. High bite force is determined by the special structure of the jaws. Serrasalmidae has a powerful complex of muscles that lead the lower jaw to the upper jaw. The thick tendon formed by the driving muscles connects to the dental bone of the relatively short lower jaw close to its anterior edge.
The food preferences of piranhas are evident in the structure of their teeth. Computer modeling of the bite using the finite element method showed a specific stress distribution within the tooth. In carnivorous species, such as Serrasalmus rhombeus or Pygocentrus nattereri, stress is concentrated in a wide ring in the middle and at the tip of the sawtooth, which is associated with high pressure on the cutting edge, whereas in the predominantly herbivorous species Piaractus brachypomus or Colossoma macropomum, stress is distributed relatively evenly in the blunt-tipped teeth. In the first case, it is possible to bite soft tissues easily, but strength to bite hard objects suffers, whereas in the second case individuals easily crush hard food.
Serrasalmidae are capable of producing various sounds. For example, when removed from the water, they begin to "bark", during fights for food they make low, drum-like sounds. In other cases, such as when one fish swims too close to another, they may carp.