''Phallichthys tico'', the dwarf merry widow, is a

livebearer Livebearers are fish that retain their eggs inside the body and give birth to live, free-swimming young. They are especially prized by aquarium owners. Among aquarium fish, livebearers are nearly all members of the family Poeciliidae and include: ...

fish from Central America. It lives in

turbid Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of both water clarity and wate ...

, stagnant waters, often among

aquatic plants Aquatic plants, also referred to as hydrophytes, are vascular plants and non-vascular plants that have adapted to live in aquatic environments ( saltwater or freshwater). In lakes, rivers and wetlands, aquatic vegetations provide cover for aquat ...

, and feeds mainly on plant matter. It is sometimes kept in aquaria.

Taxonomy and evolution

''Phallichthys tico'' appears to be the most specialized species in the genus ''

Phallichthys ''Phallichthys'' is a genus of poeciliids native to Central America. They are hardy fish which inhabit stagnant and slow-flowing waters, making them well-suited to fishkeeping. Etymology The genus name literally means "phallus (penis) fish", fro ...

''. Its

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

relationship to '' P. amates'' and '' P. fairweatheri'' is not known. Besides these two congeners, ''P. tico'' exhibits some similarity to other genera in the ''

Poecilidae Poeciliidae are a family of freshwater ray-finned 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 fami ...

'' family, most of all ''

Poeciliopsis ''Poeciliopsis'' is a genus of poeciliid fishes that primarily are native to Mexico and Central America. The only exceptions are ''P. turrubarensis'' where the range extends into Colombia, and ''P. occidentalis'' where the range extends into Ari ...

'' and '' Carlhubbsia''. Its inclusion into ''Phallichthys'' necessitated a considerable redefinition of the genus. The

specific epithet In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...

''tico'' honors

Costa Rica Costa Rica, officially the Republic of Costa Rica, is a country in Central America. It borders Nicaragua to the north, the Caribbean Sea to the northeast, Panama to the southeast, and the Pacific Ocean to the southwest, as well as Maritime bo ...

, the only country from which it was known at the time of its 1963

description Description is any type of communication that aims to make vivid a place, object, person, group, or other physical entity. It is one of four rhetorical modes (also known as ''modes of discourse''), along with exposition, argumentation, and narr ...

by the future

University of Costa Rica The University of Costa Rica (Spanish: ''Universidad de Costa Rica,'' abbreviated UCR) is a public university in the Republic of Costa Rica, in Central America. Its main campus, Ciudad Universitaria Rodrigo Facio, is located in San Pedro Mo ...

professor William Bussing.

Description

The body of ''Phallichthys tico'' is tan and robust but more elongated than that of other ''

'' species, which tend to have deeper bodies. It features 8 to 10 bars, which are somewhat obscure in adult females. The male's

gonopodium Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

is relatively long but not as much as in related species. Females grow to . Males are usually much smaller.

Distribution and ecology

''Phallichthys tico'' is known exclusively from

Lake Nicaragua Lake Nicaragua or Cocibolca or Granada (, , or ) is a freshwater lake in Nicaragua. Of tectonic origin and with an area of , it is the largest fresh water lake in Central America, the List of lakes by area, 19th largest lake in the world (by are ...

and the

tributaries A tributary, or an ''affluent'', is a stream or river that flows into a larger stream ('' main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which the ...

of the San Juan River. The species is found over muddy bottoms in stagnant,

waters such as swamps and river backwaters as well as the shorelines of Lakes Nicaragua and Arenal, where it occurs among floating

aquatic plant Aquatic plants, also referred to as hydrophytes, are vascular plants and Non-vascular plant, non-vascular plants that have adapted to live in aquatic ecosystem, aquatic environments (marine ecosystem, saltwater or freshwater ecosystem, freshwater ...

s. The temperatures range from . Though usually found in midwater, the fish frequently

browse Browsing is a kind of orienting strategy. It is supposed to identify something of relevance for the browsing organism. In context of humans, it is a metaphor taken from the animal kingdom. It is used, for example, about people browsing open sh ...

on the bottom in the shallows or swim in groups of 20–30 individuals near the surface next to grassy shores. Easily frightened, they seek cover among plants at any disturbance. The species' diet consists primarily of ooze, unicellular algae, and

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

Protozoans Protozoa (: protozoan or protozoon; alternative plural: protozoans) are a polyphyletic group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic debris. Historically ...

and

insect larvae Insects (from Latin ') are hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, ...

are occasionally taken while crustaceans are ignored.

Reproduction and husbandry

''Phallichthys tico'' is a

: the female gives birth to live young, about 12 at a time, relatively few in comparison to related species. The species is uncommon in

fishkeeping Fishkeeping is a popular hobby, practiced by aquarists, concerned with keeping fish in a home aquarium or garden pond. It is a practice that encompasses the art of maintaining one's own aquatic ecosystem, featuring a lot of variety with various w ...

despite its ease of care in the home

aquarium An aquarium (: 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. fishkeeping, Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aquati ...

. The fish tend to stay hidden among plants at the surface or the bottom and only venture out when undisturbed. They readily accept

dry food Dry or dryness most often refers to: * Lack of rainfall, which may refer to **Arid regions **Drought * Dry or dry area, relating to legal prohibition of selling, serving, or imbibing alcoholic beverages * Dry humor, deadpan * Dryness (medical) ...

References

{{Taxonbar, from=Q3764376

tico Costa Ricans (, colloquially known as ''Ticos'') are the citizens of Costa Rica, a multiethnic, Spanish-speaking nation in Central America. Costa Ricans are predominantly Mestizos, other ethnic groups people of Indigenous, European, African, and ...

Freshwater fish of Central America Fish of Costa Rica Freshwater fish of Nicaragua Fish of Lake Nicaragua Taxa named by William Bussing Fish described in 1963