#characiformes

The largest characin is the Goliath Tigerfish (Hydrocynus goliath) (image 3), which has an average adult length of 1.5 m (4.9 ft) and a weight of 50 kg (110 lb), and a maximum recorded length of about 2 m (6.6 ft) and weight of 70 kg (154 lb). The Goliath Tigerfish is known for its large, interlocking, dagger-like teeth, used for biting into prey fish. On average each of its teeth can grow up to 2.5 cm (1 in) long, comparable to the tooth size of a Great White Shark!

The Bolivian Pygmy Blue Characin (Xenurobrycon polyancistrus) is the smallest characin, with adults growing up to 1.4 cm (0.55 in) long.

Many of the most popular freshwater aquarium fish belong to this order, namely the small, colorful, peaceful “tetras”, which are often kept in tropical community tanks.

Relative to body mass, the Black Piranha (Serrasalmus rhombeus) produces one of the most forceful bites measured in vertebrates. It is also the largest species of piranha, with a maximum length of 41.5–61 centimetres (1.4-2 feet). These fish are opportunistic and omnivorous feeders which will eat plants, fallen fruits, and animals smaller than themselves such as insects and small fishes. They are also scavengers, and will feed on carcasses within the river.

The Red-bellied Piranha (Pygocentrus nattereri) (image 1) makes sounds to communicate with other members of its school, usually when exhibiting aggressive behavior such as biting, chasing, confrontation, and fighting. When handled by humans, they emit a drumming-like sound, consisting of a low-frequency harmonic sound. The sounds created by piranhas are generated through rapid contractions of the sonic muscles and is associated with the swimbladder. The swimbladder may play an important role in sound production as a resonator.

Piranhas (subfamily Serrasalminae) are some of the most misunderstood fish. While the schooling omnivores do sometimes bite bathers and swimmers, and will feed on drowned corpses, serious attacks are rare, and the fish generally avoid humans. Only two fatal attacks are known. They are eaten by humans far more often than the other way around! Their reputation as voracious predators is due to a “prank” once played on former US president Theodore Roosevelt, when he visited Brazil in 1913. Local fishermen had blocked off part of the river for days, starving the piranha in anticipation of Roosevelt’s visit. While the president watched, the fishermen pushed a cow into the water, which was quickly torn apart by the starving fish. Roosevelt went on to describe piranhas as vicious creatures which could skeletonize a cow in seconds in his 1914 book Through the Brazilian Wilderness.