# Poeciliidae

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**Poeciliidae** are a [family](/source/Family_(taxonomy)) of freshwater [ray-finned fishes](/source/Ray-finned_fish) of the order [Cyprinodontiformes](/source/Cyprinodontiformes), the tooth-carps, and include well-known [live-bearing aquarium fish](/source/Live-bearing_aquarium_fish), such as the [guppy](/source/Guppy), [molly](/source/Poecilia), [platy](/source/Platy_(fish)), and [swordtail](/source/Green_swordtail). The original distribution of the family was the [Southeastern United States](/source/Southeastern_United_States) to north of [Río de la Plata](/source/R%C3%ADo_de_la_Plata), [Argentina](/source/Argentina). Due to release of aquarium specimens and the widespread use of species of the genera *[Poecilia](/source/Poecilia)* and *[Gambusia](/source/Gambusia)* for mosquito control, though, introduced poeciliids can today be found in all tropical and subtropical areas of the world. In addition, *Poecilia* and *Gambusia* specimens have been identified in hot springs pools as far north as [Banff, Alberta](/source/Banff,_Alberta).[2]

## Live-bearing

All species in the Poecilidae are live-bearers. Differences are seen in the mode and degree of support the female gives the developing larvae. Many members of the family Poeciliidae are considered to be [lecithotrophic](/source/Lecithotrophic) (the mother provisions the [oocyte](/source/Oocyte) with all the resources it needs prior to fertilization, so the egg is independent of the mother), but others are [matrotrophic](/source/Matrotrophy) (literally "mother feeding": the mother provides the majority of resources to the developing offspring after fertilization). Lecithotrophy and matrotrophy are not discrete traits. Most scientific studies quantify matrotrophy using a matrotrophy index (MI), which is the dry mass of fully developed offspring divided by the dry mass of a fertilized egg.[3]

Members of the genus *[Poeciliopsis](/source/Poeciliopsis)*, for example, show variable reproductive life history adaptations. *[Poeciliopsis monacha](/source/Poeciliopsis_monacha)*, *[P. lucida](/source/Poeciliopsis_lucida)*, and *[P. prolifica](/source/Poeciliopsis_prolifica)* form part of the same [clade](/source/Clade) within that genus. However, their modes of maternal provisioning vary greatly. *P. monacha* can be considered to be lecithotrophic because it does not really provide any resources for its offspring after fertilization - the pregnant female is basically a swimming egg sac. *P. lucida* shows an intermediate level of [matrotrophy](/source/Matrotrophy), meaning that to a certain extent the offspring's metabolism can actually affect the mother's metabolism, allowing for increased nutrient exchange. *P. prolifica* is considered to be highly matrotrophic, and almost all of the nutrients and materials needed for fetal development are supplied to the oocyte after it has been fertilized. This level of matrotrophy allows *Poeciliopsis* to carry several broods at different stages of development, a phenomenon known as [superfetation](/source/Superfetation). Because the space for developing embryos is limited, viviparity reduces brood size. Superfetation can compensate for this loss by keeping embryos at various stages and sizes during development.[4]

*P. elongata*, *P. turneri*, and *P. presidionis* form another clade that could be considered an [outgroup](/source/Outgroup_(cladistics)) to the *P. monacha*, *P.lucida*, and *P. prolifica* clade. These three species are very highly matrotrophic - so much so that in 1947, C. L. Turner described the follicular cells of *P. turneri* as "pseudo-placenta, pseudo-chorion, and pseudo-allantois".[citation needed] The greater degree of matrotrophy in a species is linked with a higher degree of placentation, including "a thicker maternal follicle, higher degree of vascularization, and greater number of villi in the placenta".[3]

The reason for placental evolution in Poeciliids is controversial, and involves two major groups of hypotheses, adaptive and conflict hypotheses.[5] Adaptive hypotheses, including the locomotor hypothesis,[4] Trexler-DeAngelis Model[6] (reproductive allotment), and life-history facilitation,[7][5] broadly suggest that the placenta evolved to facilitate the evolution of another advantageous trait in the fish's environment. The conflict hypothesis suggests the placenta is a nonadaptive byproduct of genetic "tug-o-war" between the mother and the offspring for resources.[8]

## Taxonomy

Until recently, the egg-laying African [killifish](/source/Killifish) (genera now placed in [Procatopodidae](/source/Procatopodidae) and [Pantanodontidae](/source/Pantanodontidae)) were also placed in the Poecilidae. This treatment led to hypotheses that the Poecilidae are an ancient clade that antedate the breakup of [Gondwana](/source/Gondwana) (the split between Africa and South America) 100 million years ago, and that live-bearing subsequently evolved in South America.[9] However, more recent studies have found this taxonomic treatment to be paraphyletic, and have placed these families outside the Poecilidae. These new taxonomic treatments support that the Poecilidae are much younger than previously thought, are entirely a live-bearing group, and are only native to the Americas.[10][11]

Poeciliids colonized North America through the [Antilles](/source/Antilles), while they were connected 44 million years ago. Poeciliids then moved to Central America by the [Aves land bridge](/source/Caribbean_Plate#First_American_land_bridge) on the [Caribbean Plate](/source/Caribbean_Plate). When South America connected to Central America three million years ago, some further dispersal southward occurred, but South American species did not move into Central America.[9]

### Genera

The family is divided into [subfamilies](/source/Subfamily) and [tribes](/source/Tribe_(biology)) as follows:[1][11]

- Subfamily [Poeciliinae](/source/Poeciliinae)[12] - Tribe [Alfarini](/source/Alfarini)[13] - Genus *[Alfaro](/source/Alfaro_(fish))*[14] - Tribe [Gambusini](/source/Gambusini)[15] - Genus *[Belonesox](/source/Belonesox)*[16] - Genus *[Brachyrhaphis](/source/Brachyrhaphis)*[17] - Genus *[Gambusia](/source/Gambusia)*[18] - Genus *[Heterophallus](/source/Heterophallus)*[19] - Tribe [Heterandriini](/source/Heterandriini)[13] - Genus *[Heterandria](/source/Heterandria)*[20] - Genus *[Neoheterandria](/source/Neoheterandria)*[21] - Genus *[Poeciliopsis](/source/Poeciliopsis)*[17] - Genus *[Priapichthys](/source/Priapichthys)*[17] - Genus *[Pseudopoecilia](/source/Pseudopoecilia)*[17] - Genus *[Xenophallus](/source/Xenophallus)*[13] - Tribe [Poeciliini](/source/Poeciliini)[22] - Genus *[Limia](/source/Limia)*[18] - Genus *[Micropoecilia](/source/Micropoecilia)*[23] - Genus *[Pamphorichthys](/source/Pamphorichthys)*[17] - Genus *[Phallichthys](/source/Phallichthys)*[13] - Genus *[Poecilia](/source/Poecilia)*[24] - Genus *[Xiphophorus](/source/Xiphophorus)*[25] - Tribe [Cnesterodontini](/source/Cnesterodontini)[13] - Genus *[Cnesterodon](/source/Cnesterodon)*[26] - Genus *[Phalloceros](/source/Phalloceros)*[27] - Genus *[Phalloptychus](/source/Phalloptychus)*[27] - Genus *[Phallotorynus](/source/Phallotorynus)*[21] - Tribe [Scolichthyini](/source/Scolichthyini)[28] - Genus *[Scolichthys](/source/Scolichthys)*[28]
- Subfamily [Tomeurinae](/source/Tomeurinae) - Genus *[Tomeurus](/source/Tomeurus)*[29]
- Subfamily [Xenodexiinae](/source/Xenodexiinae) - Genus *[Xenodexia](/source/Xenodexia)*[30]

## References

1. Richard van der Laan; William N. Eschmeyer; & Ronald Fricke (2014). ["Family-group names of Recent fishes"](https://biotaxa.org/Zootaxa/article/view/zootaxa.3882.1.1/10480). *Zootaxa*. **3882** (2): 001–230. [doi:10.11646/zootaxa.3882.1.1](https://doi.org/10.11646/zootaxa.3882.1.1). [PMID 25543675](https://pubmed.ncbi.nlm.nih.gov/25543675)

1. ["Archived copy"](https://web.archive.org/web/20130509063453/http://srd.alberta.ca/FishWildlife/FisheriesManagement/documents/CostsAndThreatsOfInvasiveSpeciesInAlberta-Mar-04.pdf). Archived from [the original](http://srd.alberta.ca/FishWildlife/FisheriesManagement/documents/CostsAndThreatsOfInvasiveSpeciesInAlberta-Mar-04.pdf) on 2013-05-09. Retrieved 2013-07-26.

1. Kwan, Lucia; Fris, Megan; Rodd, F. Helen; Rowe, Locke; Tuhela, Laura; Panhuis, Tami M. (2015-03-12). ["An examination of the variation in maternal placentae across the genus Poeciliopsis (Poeciliidae)"](http://dx.doi.org/10.1002/jmor.20381). *Journal of Morphology*. **276** (6): 707–720. [Bibcode:2015JMorp.276..707K](https://ui.adsabs.harvard.edu/abs/2015JMorp.276..707K). [doi:10.1002/jmor.20381](https://doi.org/10.1002/jmor.20381). [ISSN 0362-2525](https://www.worldcat.org/issn/0362-2525). [PMID 25765517](https://pubmed.ncbi.nlm.nih.gov/25765517). [S2CID 10946526](https://api.semanticscholar.org/CorpusID:10946526)

1. Thibault, Roger E. & Schultz, R. Jack (June 1978). ["Reproductive Adaptations Among Viviparous Fishes (Cyprinodontiformes: Poeciliidae)"](http://dx.doi.org/10.2307/2407600). *[Evolution](/source/Evolution_(journal))*. **32** (2): 320–333. [doi:10.2307/2407600](https://doi.org/10.2307/2407600). [ISSN 0014-3820](https://www.worldcat.org/issn/0014-3820). [JSTOR 2407600](https://www.jstor.org/stable/2407600). [PMID 28563744](https://pubmed.ncbi.nlm.nih.gov/28563744)

1. Furness, Andrew I.; Avise, John C.; Pollux, Bart J.A.; Reynoso, Yuridia; Reznick, David N. (May 2021). "The evolution of the placenta in poeciliid fishes". *Current Biology*. **31** (9): 2004–2011.e5. [Bibcode:2021CBio...31E2004F](https://ui.adsabs.harvard.edu/abs/2021CBio...31E2004F). [doi:10.1016/j.cub.2021.02.008](https://doi.org/10.1016/j.cub.2021.02.008). [ISSN 0960-9822](https://www.worldcat.org/issn/0960-9822). [PMID 33657405](https://pubmed.ncbi.nlm.nih.gov/33657405). [S2CID 232093911](https://api.semanticscholar.org/CorpusID:232093911)

1. Trexler, Joel C. & DeAngelis, Donald L. (November 2003). ["Resource Allocation in Offspring Provisioning: An Evaluation of the Conditions Favoring the Evolution of Matrotrophy"](http://dx.doi.org/10.1086/378822). *[The American Naturalist](/source/The_American_Naturalist)*. **162** (5): 574–585. [Bibcode:2003ANat..162..574T](https://ui.adsabs.harvard.edu/abs/2003ANat..162..574T). [doi:10.1086/378822](https://doi.org/10.1086/378822). [ISSN 0003-0147](https://www.worldcat.org/issn/0003-0147). [PMID 14618536](https://pubmed.ncbi.nlm.nih.gov/14618536). [S2CID 23879988](https://api.semanticscholar.org/CorpusID:23879988)

1. Pires, Marcelo N.; Bassar, Ronald D.; McBride, Kevin E.; Regus, John U.; Garland, Theodore; Reznick, David N. (2011-03-24). ["Why do placentas evolve? An evaluation of the life-history facilitation hypothesis in the fish genus Poeciliopsis"](http://dx.doi.org/10.1111/j.1365-2435.2011.01842.x). *Functional Ecology*. **25** (4): 757–768. [Bibcode:2011FuEco..25..757P](https://ui.adsabs.harvard.edu/abs/2011FuEco..25..757P). [doi:10.1111/j.1365-2435.2011.01842.x](https://doi.org/10.1111/j.1365-2435.2011.01842.x). [ISSN 0269-8463](https://www.worldcat.org/issn/0269-8463)

1. Crespi, Bernard & Semeniuk, Christina (May 2004). ["Parent-Offspring Conflict in the Evolution of Vertebrate Reproductive Mode"](http://dx.doi.org/10.1086/382734). *The American Naturalist*. **163** (5): 635–653. [Bibcode:2004ANat..163..635C](https://ui.adsabs.harvard.edu/abs/2004ANat..163..635C). [doi:10.1086/382734](https://doi.org/10.1086/382734). [ISSN 0003-0147](https://www.worldcat.org/issn/0003-0147). [PMID 15122484](https://pubmed.ncbi.nlm.nih.gov/15122484). [S2CID 13491275](https://api.semanticscholar.org/CorpusID:13491275)

1. Hrbek, T., J. Seekinger, and A. Meyer. 2007. A phylogenetic and biogeographic perspective on the evolution of poeciliid fishes. *Molecular Phylogenetics and Evolution* **43**:986-998.

1. Bragança, Pedro H. N.; Amorim, Pedro F.; Costa, Wilson J. E. M. (2018-02-09). ["Pantanodontidae (Teleostei, Cyprinodontiformes), the sister group to all other cyprinodontoid killifishes as inferred by molecular data"](https://zse.pensoft.net/articles.php?id=22173). *Zoosystematics and Evolution*. **94** (1): 137–145. [doi:10.3897/zse.94.22173](https://doi.org/10.3897/zse.94.22173). [ISSN 1860-0743](https://www.worldcat.org/issn/1860-0743)

1. ["CAS - Eschmeyer's Catalog of Fishes"](https://researcharchive.calacademy.org/research/ichthyology/catalog/fishcatmain.asp). *researcharchive.calacademy.org*. Retrieved 2025-03-15.

1. Bonaparte, 1831 (Livebearers)

1. [Hubbs](/source/Carl_Leavitt_Hubbs), 1924

1. [Meek](/source/Seth_Eugene_Meek), 1912

1. [Gill](/source/Theodore_Nicholas_Gill), 1889

1. [Kner](/source/Rudolf_Kner), 1960

1. Regan, 1913

1. [Poey](/source/Felipe_Poey), 1854

1. Regan, 1914

1. [Agassiz](/source/Louis_Agassiz), 1853

1. [Henn](/source/Arthur_Wilbur_Henn), 1916

1. Bonaparte, 1931

1. Hubbs, 1926

1. [Bloch](/source/Marcus_Elieser_Bloch) & [Schneider](/source/Johann_Gottlob_Theaenus_Schneider), 1801

1. [Heckel](/source/Johann_Jakob_Heckel), 1848

1. [Garman](/source/Samuel_Garman), 1895

1. [Eigenmann](/source/Carl_H._Eigenmann), 1907

1. [Rosen](/source/Donn_Eric_Rosen), 1967

1. Eigenmann, 1909

1. Hubbs, 1950

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Adapted from the Wikipedia article [Poeciliidae](https://en.wikipedia.org/wiki/Poeciliidae) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Poeciliidae?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.