''Poecilia mexicana'', commonly known as the shortfin molly or Atlantic molly, is a species of

poeciliid 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 ...

fish native to fresh and

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

water in Mexico and

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 ...

. One population is found in caves and known as the cave molly.

Description

The maximum

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

of this fish is . It typically grows to a

total length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish ...

Distribution and habitat

The fish lives in tropical

freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...

and

water habitats. The shortfin molly is considered

benthopelagic The demersal zone is the part of the sea or ocean (or deep lake) consisting of the part of the water column near to (and significantly affected by) the seabed and the benthos. The demersal zone is just above the benthic zone and forms a layer of ...

. It lives in a pH range between 7.0 and 7.5 at temperatures between 22 and 28 degrees Celsius. The species does not

migrate Migration, migratory, or migrate may refer to: Human migration * Human migration, physical movement by humans from one region to another ** International migration, when peoples cross state boundaries and stay in the host state for some minimum le ...

. It is an invasive species in the Muddy River of Nevada, USA.

Ecology

Speciation

In two case studies in Cueva del Azufre and Cueva Luna Azufre in Tabasco, Mexico, the Atlantic molly is experiencing

speciation Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within ...

. It is occurring between cave and surface populations as well as between habitats of varying sulfur concentrations.

Human significance

The fishing industry has no interest in harvesting the species. However, it is sold commercially for aquariums. Occasionally, the shortfin molly is used as bait.

Etymology, taxonomy, and history

Franz Steindachner Franz Steindachner (11 November 1834 in Vienna – 10 December 1919 in Vienna) was an Austrian Zoology, zoologist, ichthyologist, and herpetologist. He published over 200 papers on fishes and over 50 papers on reptiles and amphibians. Steindachne ...

first described the species in 1863. ''Poecilia'' refers to the Greek word ''poikilos'', which means "with a lot of colours". Common names include "shortfin molly" and "Atlantic molly." The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

was found in

Orizaba Orizaba () is a city and municipality in the Mexican state of Veracruz. It is located 20 km west of its sister city Córdoba, and is adjacent to Río Blanco and Ixtaczoquitlán, on Federal Highways 180 and 190. The city had a 2005 census ...

, Mexico.

References

External links

* {{Taxonbar, from=Q525111 mexicana Taxa named by Franz Steindachner Fish described in 1863