A killifish is any of various oviparous (egg-laying) cyprinodontiform fish, including families Aplocheilidae, Cyprinodontidae, Fundulidae, Profundulidae and Valenciidae. All together, there are 1,270 species of killifish, the biggest family being Rivulidae, containing more than 320 species. As an adaptation to living in ephemeral waters, the eggs of most killifish can survive periods of partial dehydration. Many of the species rely on such a diapause, since the eggs would not survive more than a few weeks if entirely submerged in water. The adults of some species, such as Kryptolebias marmoratus, can additionally survive out of the water for several weeks. Most killies are small fish, from 2.5 to 5 centimetres, with the largest species growing to just under 15 centimetres (6 in).
The Rivulidae are a family of killifishes in the order Cyprinodontiformes. They are commonly known as rivulids, South American killifish or New World killifish. The latter names are slightly misleading, however, as they are neither restricted to South America, though most are in fact found there, nor are they the only killifishes from the Americas. Occasionally, they are still referred to as rivulines, a term dating back to when they were considered a subfamily of the Aplocheilidae.
Rivulus is a genus of small freshwater fish in the Cyprinodontiformes family Rivulidae. It was traditionally considered to be the largest genus in its family; however, the genus's size is currently in dispute. Wilson J. E. Costa split this genus into several new genera in 2004 and 2011, leaving only a few Greater Antillean species in Rivulus itself. Despite being moved to other genera, some of the species retain the common name "rivulus", like the well-known mangrove rivulus. Shortly after the review by Costa, another review authored by J.H. Huber refuted the split, moving the proposed genera back in Rivulus and again making the genus the largest in the family Aplocheilidae.
Austrolebias is a genus of killifish in the family Rivulidae. These annual killifish live in temporary pools, swamps and streams in the Río de la Plata, Patos–Mirim and Mamoré basins in South America.
Pterolebias zonatus is a species of fish in the family Aplocheilidae endemic to the Orinoco River basin in Venezuela where it is found in open waters exposed to sunlight. This species grows to a length of 10 cm (3.9 in). It is found in the aquarium trade. This species is often included in the genus Gnatholebias, of which it has been designated the type species. This species, and Pterlolebias hoignei, are rather distantly related to the other species in Pterolebias and some workers argue that their inclusion in that genus makes it paraphyletic.
Hypsolebias is a genus of small fish in the family Rivulidae that are endemic the Caatinga, Cerrado and nearby regions in Brazil. The greatest richness is in the São Francisco River basin, but there are also species in the Tocantins, Jequitinhonha and Jaguaribe systems, as well as smaller river basins in northeastern Brazil. Like their relatives, Hypsolebias are annual killifish. The short-lived adults inhabit temporary waters like rain pools, laying their eggs in the bottom. As their habitat dries up the adults die, but the eggs survive and hatch when the water returns in the next season.
Maratecoara is a genus of killifish in the family Rivulidae. These annual killifish are endemic to seasonal pools, swamps and lagoons in the upper Araguaia–Tocantins and middle Xingu river basins in Brazil. Most are from savanna regions, but M. gesmonei is from the Amazon rainforest.
Melanorivulus is a genus of South American freshwater fish in the family Rivulidae. Most species are endemic to the Río de la Plata, eastern Amazon, Tocantins–Araguaia and São Francisco basins in Brazil, but a few members of this genus range west into Bolivia, south into Paraguay and Argentina, and east to Parnaíba and Sergipe in northeastern Brazil. Only M. schuncki occurs north of the Amazon River. They inhabit shallow waters, generally 5–30 cm (2–12 in) deep, at the margins of streams in open or fairly open habitats like the Cerrado or Cerrado–Amazon transition. Many have tiny ranges and are seriously threatened.
Anablepsoides is a genus of killifish in the family Rivulidae native to tropical South America and the Lesser Antilles. The majority are from the Amazon and Orinoco basins, as well as freshwater systems in the Guiana Shield, but a few species are from northern Venezuela, northeastern Brazil and the Lesser Antilles. Although largely restricted to lowlands, a few species occur in the lower East Andean foothills. They are mostly found in shallow fresh water swamps, streams, edges of rivers, ponds and pools, but a few may occur in brackish estuaries. They are able to jump over land and breathe air for short periods, allowing them to access isolated waters inhabited by few or no other fish. Several Anablepsoides species have small distributions and some are seriously threatened by habitat loss; the entire known range of A. xinguensis is in the area flooded by the Belo Monte Dam.
Cynodonichthys is a genus of freshwater killifish in the family Rivulidae. They are found in Middle America, ranging from southern Mexico, through Central America, to Colombia. They are non-annual killifish and inhabit small forest streams from the lowlands to an altitude of 1,500 m (4,900 ft).
Laimosemion is a genus of fish in the family Rivulidae from the Amazon basin and basins in the Guiana Shield in tropical South America. They mostly inhabit small streams, creeks, swamps and pools in lowlands, but locally occur to an altitude of 1,300 m (4,300 ft).
Moema is a genus of fish in the family Rivulidae. These annual killifish are mostly restricted to the Amazon basin in Bolivia, Brazil and Peru, but a few inhabit the upper Essequibo basin in Guyana, upper Orinoco basin in Venezuela and upper Paraguay basin in Brazil. They inhabit temporary waters, such as swamps or ponds, in primary forests. Once the water disappears, the adults die, but the eggs that have been laid in the bottom remain, only hatching after 3–10 months when the water returns. They rapidly reach adult size, but generally only live a few months after hatching, although captives can live longer.
Neofundulus is a genus of fish in the family Rivulidae. These annual killifish are endemic to the Paraguay, Guaporé, Mamoré and São Francisco basins in Argentina, Bolivia, Brazil and Paraguay. They inhabit temporary waters, such as swamps or ponds, that typically are located in open habitats like grassland. Once the water disappears, the adults die, but the eggs that have been laid in the bottom remain, only hatching after several months when the water returns.
Papiliolebias is a genus of fish in the family Rivulidae. These annual killifish are endemic to seasonal pools in the Paraguay and upper Madeira river basins in northwestern Argentina, central and southeastern Bolivia, and western Paraguay.
Pituna is a genus of fish in the family Rivulidae. These annual killifish are endemic to seasonal pools, swamps and lagoons in the Araguaia–Tocantins, Xingu, uppermost Paraná and Paranaíba river basins in Brazil. Most are from savanna regions, but P. xinguensis is from the Amazon rainforest.
Plesiolebias is a genus of fish in the family Rivulidae. These annual killifish are endemic to seasonal pools, swamps and lagoons in the Araguaia–Tocantins, Xingu, and uppermost Paraguay (Pantanal) river basins in Brazil.
Rachovia is a genus of killifish from the family Rivulidae the species of which are endemic to the Orinoco, Maracaibo and Magdalena basins in Colombia and Venezuela, where they live in small temporary waters like ponds. They are small annual killifish that reach up to 6 cm (2.4 in) in total length. The name of this genus honours the German aquarist Arthur Rachow (1884–1960) who sent fish specimens to George S. Myers.
Simpsonichthys is a genus of killifish from the family Rivulidae the species of which are endemic to temporary freshwater habitats like ponds in the upper Paraná, upper Araguaia, upper Jequitinhonha and São Francisco basins on the central Brazilian Plateau. They are small annual killifish that reach up to 5.5 cm (2.2 in) in standard length.
Stenolebias is a genus of fish in the family Rivulidae. These relatively rare annual killifish are endemic to seasonal waters in the Pantanal in Brazil.
Simpsonichthys nielseni is a species of killifish from the family Rivulidae. It is found in the São Francisco River basin in Brazil in South America.
