Astyanax is a genus of freshwater fish in the family Characidae of the order Characiformes. Some of these fish, like many of their relatives, are kept as aquarium pets and known collectively as tetras. With around 150 described species and new ones being described yearly, this genus is among the largest of the entire order; Hyphessobrycon also has more than 145 species and which one is larger at any one time depends on whether more species have been recently described in one or the other. The blind and colorless cave tetra of Mexico is a famous member of the genus, but its taxonomic position is disputed: Some recognize it as part of the Mexican tetra and this is supported by phylogenetic evidence, but others recognize the cave form as a separate species, A. jordani.
Charax is a genus containing several species of South American tetras, including the glass headstander, C. gibbosus. These fish, among other characteristics, are small and have a rhomboid shape. Some species are semi-translucent.
Rineloricaria is a genus of freshwater tropical catfish belonging to the Loricariidae family. They are commonly called whiptail catfish because of the long filament that grows out of the tip of the caudal fin that is characteristic of the genus. With the exception of R. altipinnis from Panama, they are native to the rivers of northern and central South America. Some species are regularly seen in the aquarium trade.
Gymnogeophagus is a genus of cichlid fishes from South America, where they are known from various river basins in southern Brazil, Paraguay, Uruguay and northern Argentina. They are part of a group popularly known as eartheaters.
Laetacara is a small genus of cichlids native to soft, acidic freshwater habitats in South America. The genus is also collectively known as the smiling acaras. The range of the genus extends from the upper Orinoco River in Venezuela to the Paraná River in Paraguay. Like all cichlids, Laetacara species have well-developed brood care.
Mesonauta, the flag cichlids, is a small genus of cichlids native to the Amazon, Orinoco, Essequibo, Paraná and Paraguay basins in South America. Mesonauta is included in the subfamily Cichlasomatinae. They occur in various freshwater habitats such as streams and lakes, especially in areas with little water movement and aquatic vegetation. They are generally found in small groups that stay near the water surface. To avoid predators, adults may jump out of the water and juveniles mimic leaves.
Pimelodus is a genus of fish in the family Pimelodidae native to Central and South America.
Hisonotus is a genus of armored catfishes native to South America. Species of Hisonotus and Curculionichthys are the only representatives of the subfamily Otothyrinae having serrae on the posterior edge of the pectoral fin spine. These species are small fishes, generally found in small fast flowing streams, where they grasp to the branches and leaves of aquatic or subaquatic plants. The species of this genus mostly occur in Atlantic coastal streams of southern Brazil and the Paraguay-Paraná system of southern South America. They are also distributed in the Río de La Plata basin and coastal rivers of southeastern Brazil.
Bryconops is a genus of fish in the family Characidae from South America.
Moenkhausia is a genus of freshwater fish in the family Characidae native to tropical and subtropical South America. These are medium-sized tetras where the largest species only reach around 12 cm (4.7 in).
Odontesthes is a genus of Neotropical silversides. They are found in fresh, brackish and salt water habitats in the southern half of South America, as well as the offshore Juan Fernández and Falkland Islands. Additionally, O. bonariensis has been introduced to other continents.
Bryconamericus is a genus of characins found in Central and South America.
Deuterodon is a genus of characins from river basins in southern and southeastern Brazil, with a single species of uncertain taxonomic status, D. potaroensis, from Guyana. These are small fish that reach up to 12.6 cm (5.0 in) in total length. They are omnivores with a specialized mouth structure that allows them to scrape algae and debris off bedrock.
Hemibrycon is a genus of characins. They are mainly found in South America, with the single exception being H. dariensis of east Panama.
Odontostilbe is a genus of characins from tropical Central and South America, with 17 currently recognized species:
Phenacogaster is a genus of characins from South America, with 20 currently described species:
Serrapinnus is a genus of characins from tropical South America.
Spintherobolus is a genus of characins that are endemic to river basins in southern and southeastern Brazil from Santa Catarina to Rio de Janeiro. All four species in the genus are considered threatened by Brazil's Ministry of the Environment. They are small fish, up to 6.1 cm (2.4 in) in standard length.
Loricariichthys edentatus is a species of catfishes found in Entre Rios Province, Argentina. It has no teeth on the premaxilla, a unique feature in the Loricariichthys genus.
Mesonauta acora is a species of cichlid fish native to blackwater in the Xingu and Tocantins River basins in South America. The species was named by François Louis de la Porte, comte de Castelnau in 1855.
