Characins: Order Characiformes

The order Characiformes is a relatively large group with about 2236 species. Fish in this order are often refered to commonly as characins or leoporins. They have a huge diversity of forms from predators to planktivores. In part because of this diversity they are one of the most popular orders in the aquarium fish trade. Taxonomically they are closely related to the Cypriniformes (carps, minnows, loaches, barbs, goldfish), the Gymnotiformes (South American Knife-fishes) and the Siluriformes (catfish) - together these fish make up a series called the Otophysi.

Unique Descriptive Features

There are a few distinquishing characteristics of characins that make them easy to recognize. First, while fish in the order Characiformes are closely related to catfish and knifefish, they almost always have scales (the South American tetra - Gymnocharacinus bergi of Argentina is one exception). In particular they have ctenoid scales as opposed to the cylcloid scales found in lower groups. Second, these is a fleshy second fin behind the dorsal fin (called an adipose fin) - a characteristic that helps distinguish them from cyprinformes (carps, minnows and loaches). Finally, the barbels that are so typical of catfish and loaches, are mostly absent.

Classification

There are approximately 2236 species (according to Fishbase) of fish named in the order Cypriniformes (1674 according to the 2006 printing of Nelson's Fishes of the World). The following families make up the order:

Acestrorhynchidae (Freshwater barracuda) - 15 species
Alestidae (African tetras such as the Congo tetra and the African tigerfish) - 110 species
Anostomidae (Anostomids such as the headstander and boga) - 140 species
Characidae (Characids like Piranha, blind cave tetra, red phantom tetra, and costello tetra) - 776
Chilodontidae (headstanders) - 8 species
Citharinidae (African moonfish, etc) - 8 species
Crenuchidae (South American darters) - 74 species
Ctenoluciidae (Pike-characin) - 7 species
Curimatidae (Toothless characins) - 95 species
Cynodontidae (dogteeth tetras) - 14 species
Distichodontidae (African Characins) - 90 species
Erythrinidae
Gasteropelecidae
Hemiodontidae
Hepsetidae
Lebiasinidae
Parodontidae
Prochilodontidae (Flannel-mouthed characins)

Common Characins in the Aquarium Fish Trade

Why are Characins and Tetras in the Aquarium Trade?

Characins, tetras and the other members that make up the order Characiformes contribute to an extremely popular group of fishes for hobbyists. In fact, they are the second most popular fish order in the aquarium hobby, just behind the closely related Cypriniformes (goldfish, loaches, carps etc). The popularity of these fish can be attributed to their general docile behavior, schooling tendencies, striking marking, and ease of care. The above thumbnail list of popular characins is but a few of the total number of species found in aquariums. While only a small selection of the 2236 known species end up in large pet stores, many more can be purchased from specialty hobbyists.

The Pirhana

In addition to the various popular aquarium species, the most notorious characid is the piranha. The subfamily Serrasalminae (which includes the piranha) contains about 60 species, some of which are predatory, others that are scale-eating opportunists and specialists, and some that are largely herbivorous, such as the pacus and silver dollars. Despite their reputation and potential for doing damage, many purported attacks on humans by piranhas actually result from postmortem scavenging on drowning victims. The large herbivorous species are important food fishes in the Amazon basin. They are also important dispersers of seeds during the wet season, particularly because they use their massive dentition to husk seeds , which may aid germination.