A killifish is any of various oviparous (egg-laying) cyprinodontiform fish

Cyprinodontiformes

The Cyprinodontiformes is an order of ray-finned fish, comprising mostly small, fresh-water fish. Many popular aquarium fish, such as killifish and live-bearers, are included. They are closely related to the Atheriniformes and are occasionally included with them...

 (including families Aplocheilidae

Aplocheilidae

Aplocheilidae are a family of bony fishes containing about 15 species. Formerly, the name "Aplocheilidae" was used for the Aplocheiloidei as a whole, i.e. including the Nothobranchiidae of Africa and the mainly South American Rivulidae as subfamilies. This obsolete system is sometimes still seen,...

, Cyprinodontidae, Fundulidae

Fundulidae

Fundulidae is the family of topminnows and North American killifishes. 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....

, Nothobranchiidae

Nothobranchiidae

Nothobranchiidae are a family of bony fishes containing roughly 300 species. They are small killifish, usually measuring about . They are essentially limited to Africa, and were formerly included in the family Aplocheilidae...

, Profundulidae

Profundulidae

Profundulidae is a family of teleost fish endemic to Mexico, Guatemala and other countries of Central America. This family is monotypic with only a single genus, Profundulus...

, Rivulidae

Rivulidae

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...

 and Valenciidae). Altogether, there are some 1270 different species of killifish, the biggest family being Rivulidae, containing more than 320 species. Although killifish is sometimes used as an English equivalent to Cyprinodontidae, some species belonging to that family have their own common names, such as the pupfish

Pupfish

Pupfish are a group of small killifish belonging to ten genera of the family Cyprinodontidae of ray-finned fish. All pupfish are especially noted for being found in extreme and isolated situations, in various parts of North America, South America, and the Caribbean region...

 and the mummichog

Mummichog

The mummichog is a killifish also known as mummies, gudgeons, and mud minnows are found in brackish and coastal waters along the eastern seaboard of the United States as well as Atlantic Canada. It is noted for its hardiness and for being a popular research subject in embryological, physiological,...

. The name killifish is derived from the Dutch

Dutch language

Dutch is a West Germanic language and the native language of the majority of the population of the Netherlands, Belgium, and Suriname, the three member states of the Dutch Language Union. Most speakers live in the European Union, where it is a first language for about 23 million and a second...

 word "kilde", meaning small creek, puddle. Because of living in ephemeral waters, the eggs of most killifish can survive periods of partial dehydration. Like seeds, the eggs can be sent by mail without water. Most killies are small fish, from one to two inches (2.5 to 5 cm), with the largest species growing to just under six inches (15 cm).

Range and habitat

Killifish are found mainly in fresh or brackish waters in the Americas, as far south as Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 and as far north as southern Ontario

Ontario

Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

. There are also species in southern Europe

Europe

Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...

, in much of Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

 as far south as KwaZulu-Natal

KwaZulu-Natal

KwaZulu-Natal is a province of South Africa. Prior to 1994, the territory now known as KwaZulu-Natal was made up of the province of Natal and the homeland of KwaZulu....

, South Africa

South Africa

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

, in the Middle East and Asia (as far east as Vietnam

Vietnam

Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

), and on several Indian Ocean islands. Killifish are not found in Australia, Antarctica, or northern Europe.

The majority of killifish are found in permanent streams, rivers, and lakes, and live between two and three years. Such killifish are common in the Americas (Cyprinodon

Cyprinodon

Cyprinodon is a genus of small killifish belonging to the family Cyprinodontidae of ray-finned fish.-Species:* Whitefin pupfish, Cyprinodon albivelis Minckley & Miller, 2002.* Potosi pupfish, Cyprinodon alvarezi Miller, 1976....

, Fundulus

Fundulus

Fundulus is a genus of ray-finned fishes in the superfamily Funduloidea, family Fundulidae . They belong to the order of toothcarps , and therein the large suborder Cyprinodontoidei...

and Rivulus

Rivulus

Rivulus is a genus of freshwater fish in the Rivulidae family of Cyprinodontiformes. Over one hundred species of Rivulus have been described to date, some of them finding a degree of popularity among aquarists, especially killifish fanciers...

) as well as in Africa and Asia (including Aphyosemion, Aplocheilus

Aplocheilus

Aplocheilus is a genus of killifish in the family Aplocheilidae, with 7 species. Their range is primarily South and Southeast Asia, from Pakistan to Vietnam and Malaysia, and from Nepal to Sri Lanka. Several species, especially the striped panchax, Aplocheilus lineatus, are important aquarium fishes...

, Epiplatys, Fundulopanchax and Lacustricola) and southern Europe (Aphanius

Aphanius

Aphanius is a genus of fish in the Cyprinodontidae family.It contains the following species:* Aphanius anatoliae* Aphanius apodus* Aphanius baeticus* Aphanius burduricus* dislisazancik baligi...

). Some of these habitats can be rather extreme; the only natural habitat of the Devils Hole pupfish (Cyprinodon diabolis) is Devils Hole: a cavern at least 300 feet (91.4 m) deep, branching out from a small opening at the surface, approximately 6 feet (1.8 m) by 18 feet (5.5 m) wide.

Some specialized forms live in temporary ponds and flood plains, and typically have a much shorter lifespan. Such species, known as "annuals", live no longer than nine months, and are used as models for studies on aging. Examples include the African genus Nothobranchius

Nothobranchius

Nothobranchius is a genus of freshwater annual fish from East Africa in the family Nothobranchiidae which was long included in the Aplocheilidae. Many species have very small distributions. There are many species: as of April 2010 there are a total of 54 nominal species, not counting subspecies...

and South American genera ranging from the cold water Austrolebias of Argentina

Argentina

Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 and Uruguay

Uruguay

Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...

 to the more tropical Gnatholebias, Pterolebias, Simpsonichthys and Terranatos.

Territorial behavior

A small number of species will shoal while most are territorial to varying degrees. Populations can be dense and territories can shift quickly, especially for species of the extreme shallows (a few centimetres of water). Many species exist as passive tribes in small streams where dominant males will defend a territory while allowing females and immature males to pass through the area. In the aquarium, territorial behavior is different for every grouping, and will even vary by individuals. In a large enough aquarium, most species can live in groups as long as there are more than three males.

Diet

Killifish feed primarily on aquatic arthropods such as insect (mosquito

Mosquito

Mosquitoes are members of a family of nematocerid flies: the Culicidae . The word Mosquito is from the Spanish and Portuguese for little fly...

) larva

Larva

A larva is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle...

e, aquatic crustacean

Crustacean

Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...

s and worms. It is reported by the killifish collector Rudolf Koubek that areas in Gabon

Gabon

Gabon , officially the Gabonese Republic is a state in west central Africa sharing borders with Equatorial Guinea to the northwest, Cameroon to the north, and with the Republic of the Congo curving around the east and south. The Gulf of Guinea, an arm of the Atlantic Ocean is to the west...

 where the streams lack killifish (due to pollution or other causes) are rife with malaria

Malaria

Malaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...

, which is spread by a mosquito. Some species of Orestias from Lake Titicaca

Lake Titicaca

Lake Titicaca is a lake located on the border of Peru and Bolivia. It sits 3,811 m above sea level, making it the highest commercially navigable lake in the world...

 are plankton

Plankton

Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...

ic filter feeder

Filter feeder

Filter feeders are animals that feed by straining suspended matter and food particles from water, typically by passing the water over a specialized filtering structure. Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish and some sharks. Some birds,...

s. Others, such as Cynolebias and Megalebias species and Nothobranchius ocellatus are predatory and feed mainly on other fish. The American Flagfish (Jordanella floridae) feeds heavily on algae and other plant matter as well as aquatic invertebrates.

Killifish as pets

Many killifish are lavishly coloured; and most species are easy to keep and breed in an aquarium

Aquarium

An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...

. Specimens can be obtained from specialist societies and associations. Striped panchax

Striped panchax

The striped panchax, Aplocheilus lineatus, is a species of killifish, of the genus Aplocheilus. An aquarium variant of this species with a more yellowish coloration is known as golden wonder killifish. The striped panchax inhibits fresh and brackish waters of India and Sri Lanka. It is found in...

(aka. Golden Wonder) are commonly found in pet shops, but caution must be exercised when considering tank mates, since the mouth of the Striped panchax is as wide as the head, and much smaller fish will be eaten. Flagfish, native to south Florida, are another species of killifish commonly found in pet stores. They are useful in aquariums for algae control.

External links

• killi.net - Articles, taxonomy, and images of nearly 700 species
• American Killifish Association (AKA)
• British Killifish Association (BKA)
• Itrainsfishes - All about South American Killifishes
• Rare Hermaphroditic Fish Survives in Mangrove Swamps - D. Scott Taylor, Ph.D - mangrove.org