Poecilia

Key takeaways

Poecilia belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Poecilia to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Poecilia from memory before moving on to harder problems.

Reference excerpt

Poecilia is a genus of fishes in the family Poeciliidae of the order Cyprinodontiformes. These livebearers are native to fresh, brackish and, saltwater in the Americas, and some species in the genus are euryhaline. A few have adapted to living in waters that contain high levels of toxic hydrogen sulfide (H2S), and a population of P. mexicana lives in caves (other populations of this species are surface-living). Some common and widespread species are often kept as aquarium fish, while others have very small ranges and are seriously threatened. Species in Poecilia are called mollies (e. g. P. sphenops) or guppies (e. g. P. reticulata) depending on body shape. Micropoecilia has been proposed to be included as a subgenus of Poecilia.

Taxonomy and etymology Poecilia was first proposed as a genus in 1801 by the German naturalists Marcus Elieser Bloch and Johann Gottlob Theaenus Schneider when the described Poecilia vivipara as a new species. P. vivipara was subsequently designated as the type species of the genus by Pieter Bleeker in 1864. It is the type genus of the subfamily Poeciliinae and of the family Poeciliidae. Poecilia refers to the Greek word poikilos, which means "variegated" or "speckled", an allusion to the coloration and pattern of the type species, as well as that of and other related fishes, such as Fundulus heteroclitus which Bloch & Schneider classified in this genus.

In aquaria Fish of this genus have extremely variable coloration and have been selectively bred to create many different varieties. The most commonly kept species are guppies (P. reticulata), mollies (P. sphenops or P. latipinna), and Endler's livebearers (P. wingei). Members of the genus readily hybridize with each other and so most commercially offered fish are hybrids (with guppies having some Endler, and mollies being a mix of common and sailfin mollies).

They are easy to sex as males have a prominent gonopodium, a modified anal fin used to inseminate females. They mature quickly and breed readily, with females giving birth to a dozen or more fry every month. Some poecilids are cannibalistic and will eat any of their fry that are unable to flee in time (with females often eating the fry they just gave birth to, especially in a cramped aquarium setting).

Species The following species are recognized in the genus Poecilia:

Poecilia akroa Figueiredo & Moreira, 2018 Poecilia araguaiensis (Costa, 1991) Poecilia bifurca (C. H. Eigenmann, 1909) Poecilia boesemani Poeser, 2003 Poecilia branneri Eigenmann, 1894 Poecilia butleri D. S. Jordan, 1889 (Pacific molly) Poecilia catemaconis R. R. Miller, 1975 (Catemaco molly) Poecilia caucana (Steindachner, 1880) (Cauca molly) Poecilia caymanensis (Rivas & Fink, 1970) Poecilia chica R. R. Miller, 1975 (dwarf molly) Poecilia dauli M. K. Meyer & Radda, 2000 Poecilia dominicensis (Evermann & H. W. Clark, 1906) Poecilia elegans (Trewavas, 1948) (elegant molly) Poecilia formosa (Girard, 1859) (Amazon molly) Poecilia fuscomaculata (Rivas, 1980) Poecilia garnieri (Rivas, 1980) Poecilia gillii (Kner, 1863) Poecilia grossidens (Rivas, 1980) Poecilia hasemani (Henn, 1916) Poecilia heterandria (Regan, 1913) Poecilia hispaniolana Rivas, 1978 (Hispaniola molly) Poecilia hollandi (Henn, 1916) Poecilia hondurensis Poeser, 2011 Poecilia immaculata (Rivas, 1980) Poecilia islai (Rodriguez-Silva & Weaver, 2020) Poecilia koperi Poeser, 2003 Poecilia kykesis Poeser, 2002 Poecilia latipinna (Lesueur, 1821) (sailfin molly) Poecilia latipunctata Meek, 1904 (broadspotted molly) Poecilia limantouri Jordan & Snyder, 1899 Poecilia mandibularis (Rodriguez-Silva, Torres-Pineda & Josaphat, 2020) Poecilia marcellinoi Poeser, 1995 Poecilia maylandi M. K. Meyer, 1983 (Balsas molly) Poecilia mechthildae M. K. Meyer, Etzel & Bork, 2002 Poecilia melanogaster Günther, 1866 Poecilia melanonotata (Nichols & Myers, 1923) Poecilia mexicana Steindachner, 1863 (shortfin molly) Poecilia minima Costa & Sarraf, 1997 Poecilia minor (Garman, 1895) Poecilia miragoanensis (Rivas 1980) Poecilia montana Rosen & Bailey, 1963 Poecilia nelsoni (Meek, 1904) Poecilia nigrofasciata (Regan, 1913) Poecilia obscura Schories, M. K. Meyer & Schartl, 2009 Poecilia ornata (Regan, 1913) Poecilia orri Fowler, 1943 (mangrove molly) Poecilia pallida (de Buen, 1943) Poecilia parae C. H. Eigenmann, 1894 (Melanzona guppy) Poecilia pauciradiata (Rivas, 1980) Poecilia pertapeh (Figueiredo, 2008) Poecilia perugiae (Evermann & Clark, 1906) Poecilia petenensis Günther, 1866 (Peten molly) Poecilia picta (Regan, 1913) (Swamp guppy) Poecilia reticulata W. K. H. Peters, 1859 (guppy) Poecilia rivasi (Franz & Burgess, 1983) Poecilia rositae M. K. Meyer, K. Schneider, Radda, B. Wilde & Schartl, 2004 Poecilia salvatoris Regan, 1907 (Liberty molly) Poecilia sarrafae Bragança & W. J. E. M. Costa, 2011 Poecilia scalpridens (Garman, 1895) Poecilia sphenops Valenciennes, 1846 (black molly) Poecilia sulphuraria (Álvarez, 1948) (sulphur molly) Poecilia sulphurophila (Rivas, 1980) Poecilia teresae D. W. Greenfield, 1990 (mountain molly) Poecilia thermalis Steindachner, 1863 Poecilia tridens Hilgendorf, 1889 Poecilia vandepolli van Lidth de Jeude, 1887 Poecilia velifera (Regan, 1914) (Yucatán molly) Poecilia versicolor (Günther, 1866) Poecilia vittata Guichenot, 1843 Poecilia vivipara Bloch & J. G. Schneider, 1801 Poecilia waiapi Bragança, W. J. E. M. Costa & Gama, 2012 Poecilia wandae Poeser, 2003 Poecilia wingei Poeser, Kempkes & Isbrücker, 2005 (Endler's guppy, Endler's livebearer) Poecilia yaguajali (Rivas, 1980) Poecilia zonata (Nichols, 1915) If Poecilia in the wider sense is used then the species would be divided up into subgenera as follows:

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Poecilia

Start with the simplest possible case. Write down what Poecilia claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Poecilia before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Poecilia ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Poecilia

In research: Poecilia appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Poecilia in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Poecilia is common in secondary-school and first-year university syllabi. It links to neighbouring topics Actinopterygii genera, Freshwater fish genera, Live-bearing fish, so understanding it makes those chapters shorter.
In everyday life: Look for Poecilia outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Poecilia in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Poecilia means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Poecilia out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Poecilia in simple terms?

Poecilia is a genus of fishes in the family Poeciliidae of the order Cyprinodontiformes. These livebearers are native to fresh, brackish and, saltwater in the Americas, and some species in the genus are euryhaline.

Why does Poecilia matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Poecilia?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Poecilia.