''Heterandria'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of livebearing fishes within the family

Poeciliidae The Poeciliidae are a family of freshwater fishes of the order Cyprinodontiformes, the tooth-carps, and include well-known live-bearing aquarium fish, such as the guppy, molly, platy, and swordtail. The original distribution of the family was t ...

. Most

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

occur in

Guatemala Guatemala ( ; ), officially the Republic of Guatemala ( es, República de Guatemala, links=no), is a country in Central America. It is bordered to the north and west by Mexico; to the northeast by Belize and the Caribbean; to the east by H ...

and its surroundings, particularly

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, but the midget livebearer ('' H. formosa'') comes from the southeastern

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

. Though many Poecilidae are familiar

aquarium An aquarium (plural: ''aquariums'' or ''aquaria'') is a vivarium of any size having at least one transparent side in which aquatic plants or animals are kept and displayed. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...

fishes, e.g.

guppies The guppy (), also known as millionfish and rainbow fish, is one of the world's most widely distributed tropical fish and one of the most popular List of freshwater aquarium fish species, freshwater aquarium fish species. It is a member of the ...

, mollies, platys and

swordtail ''Xiphophorus'' is a genus of euryhaline and freshwater fishes in the family Poeciliidae of order Cyprinodontiformes, native to Mexico and northern Central America. The many ''Xiphophorus'' species are all known as platyfish (or platies) and s ...

s, species within ''Heterandria'' are not commonly kept as fish. Somewhat more frequently found in aquaria is ''H. formosa'', perhaps because it is one of the smallest known fish species in the world; its diminutive males are probably the smallest fish easy to keep as a pet. Species in this genus resemble egg-laying

Cyprinodontoidei Cyprinodontoidei is a suborder of fishes, one of the two suborders in the Order (biology), order Cyprinodontiformes. The Cyprinodontoidei consists of four suoerfamily, superfamilies which are found in the Americas, the Mediterranean and in Africa ...

such as

Fundulidae Fundulidae is the family of topminnows and North American killifishes. Distribution The 46 species are native to North America as far south as Yucatan, and to the islands of Bermuda and Cuba, occurring in both freshwater and marine environments. ...

(topminnows) at first glance, and are thus sometimes called "

killifish 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 ...

" though this is technically erroneous.

FishBase FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.

(2009)
''Heterandria'' species
Retrieved April 8, 2009.

Species

FishBase FishBase is a global species database of fish species (specifically finfish). It is the largest and most extensively accessed online database on adult finfish on the web.

currently recognize 3 species in this genus, but based on

genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...

, external characters,

morphometrics Morphometrics (from Greek μορϕή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are co ...

and

meristics Meristics is an area of ichthyology and herpetology which relates to counting quantitative features of fish and reptiles, such as the number of fins or scales. A meristic (countable trait) can be used to describe a particular species of fish, or us ...

''H. formosa'' (the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

of the genus) is not closely related to the remaining, which have been moved to their own genus, ''Pseudoxiphophorus''.Agorreta, A.; Domínguez-Domínguez, O.; Reina, R.G.; Miranda, R.; Bermingham, E.; and Doadrio, I. (2013). ''Phylogenetic relationships and biogeography of Pseudoxiphophorus (Teleostei: Poeciliidae) based on mitochondrial and nuclear genes.'' Mol Phylogenet Evol. 2013 Jan;66(1):80-90 There are probably more remaining undiscovered as these fishes are rather inconspicuous. However, it is not very likely that many species remain unknown to science as this genus is only found in a rather restricted region, and only one new species has been discovered since 1980. The three species classified under this genus are: * ''

Heterandria attenuata ''Heterandria'' is a genus of livebearing fishes within the family Poeciliidae. Most species occur in Guatemala and its surroundings, particularly Mexico, but the midget livebearer ('' H. formosa'') comes from the southeastern United States ...

'' D. E. Rosen & R. M. Bailey, 1979 * '' Heterandria formosa'' Girard, 1859 (Dwarf livebearer, least killifish) * ''

Heterandria tuxtlaensis ''Heterandria'' is a genus of livebearing fishes within the family Poeciliidae. Most species occur in Guatemala and its surroundings, particularly Mexico, but the midget livebearer ('' H. formosa'') comes from the southeastern United State ...

'' McEachran & T. J. DeWitt, 2008

References

{{Taxonbar, from=Q3134793 Poeciliidae Ovoviviparous fish Fish of Central America Freshwater fish of Mexico Fish of the United States Freshwater fish genera Taxa named by Louis Agassiz Ray-finned fish genera de:Heterandria