this is piranha

• Body Shape
  All piranha-species have a powerful, high, thick but laterally compressed body shape, with keel-like edges running over the upper part of the body from head to dorsal fin, and on the lower body running over the belly. Together with a powerful large tail and a body covered with very small scales, their streamlined bodies make them very fast and agile swimmers.
  The oddball in the group, body shape wise is Serrasalmus elongatus, the Elongated or Pike Piranha. This species has a salmon-like, elongated and slender body, but with the same powerful, well developed tail. It is said to be the fastest swimmer of all piranha species.
  Unlike many fish-species, piranhas have a small adipose fin between tail and dorsal fin. This feature is characteristic for the Characin-family, although members from some other families, like catfish, have an adipose fin as well.


• Eyes and Nose
  The large eyes and a large nose with big nostrils to maximize the water inflow reflect the predatory lifestyle of piranhas. They have a very acute sense of smell. In their natural habitat, the murky rivers in South-America even more darkened by overhanging vegetation; scent is their main way of tracking down their prey.


• Teeth
  The piranha's unmistakable trademark features are the triangular, razor sharp teeth; large ones in the lower jaw and smaller ones in the upper jaw. When the mouth is closed, the teeth from both jaws fit exactly, comparable to a bear-trap. This enables them to slice off pieces of meat or fins or scales, literally taking apart their prey piece by piece. Their teeth are replaceable, when a tooth is broken off a new one grows to replace it.

• Visual Traits by Genus
  Beyond the basic characteristics of all Piranha fish species, there are different visual traits depending on the genera. Traits of Pygocentrus and Serrasalmus genera are:
  • Pygocentrus
    Members from the genus Pygocentrus are all recognizable by the convex shape of their head and massive bulldog-like lower jaw. It is more powerful and muscular than most Serrasalmus species.
    Besides being scavengers, if necessary all Pygocentrus species are full blown predators as well, that actively give chase to their prey.
  • Serrasalmus
    Serrasalmus piranha's have a more concave head shape, and a less powerful lower jaw than the Pygocentrusspecies.
    A number of species feed themselves mainly on fins and scales of other fish, and even nuts and fruits, and therefore they do not need the same muscle packed lower jaw to rip through skin, muscle and bone. This does not apply every species of this group, however. A few, are true predators when adults, and do have very massive and powerful jaws as well.