''Nannostomus'' (from the

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

''nanos'' = small, and the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

''stomus'' = relating to the mouth) is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

belonging to the

characin Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras.; Buckup P.A.: "Relationsh ...

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Lebiasinidae The Lebiasinidae are a family (biology), family of freshwater fishes found in Costa Rica, Panama, and South America. They are usually small and are known as ornamental fishes in Aquarium, aquaria, including popular fishes such as the various penc ...

. All of the species in this genus are known as pencil fish, a popular name that was initially only applied to two species in the 1920s, '' Nannostomus unifasciatus'' and '' Nannostomus eques'', by the late 1950s however, the term would be applied to all members of the genus. Several species have become popular

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 ...

fish due to their attractive coloration, unique shape, and interesting demeanor.

Taxonomy

The genus ''Nannostomus'' was first described by Günther in 1872 with the

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, '' N. beckfordi''. In 1876,

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

described three more species, '' N. unifasciatus'', '' N. eques'' (pictured below), and '' N. trifasciatus'' (pictured above). In 1909,

Carl H. Eigenmann Carl Henry Eigenmann (March 9, 1863 – April 24, 1927) was a German-American ichthyology, ichthyologist of the late nineteenth and early twentieth centuries, who, along with his wife Rosa Smith Eigenmann, and his zoology students is credited wit ...

described '' N. marginatus'', '' N. minimus'', '' N. erythrurus'' and '' N. harrisoni''. Several of these have been popular with aquarists since the early 20th century, partly due to enthusiastic articles written about them and photographs taken by William T. Innes that were published as early as 1933. Over the years, the genus was split by subsequent authors into other genera, including ''Poecilobrycon'' and ''Nannobrycon''. After nearly a century of debate on the subject, Dr.

Stanley Howard Weitzman Stanley Howard Weitzman (born March 16, 1927, in Mill Valley, California; died February 16, 2017) was a Research Scientist Emeritus at Division of Fishes, National Museum of Natural History, Washington, D.C. Life and career He received his Bache ...

and Dr. J. Stanley Cobb restored earlier taxonomy and expanded upon it, unifying all species under ''Nannostomus'' in 1975. This comprehensive revision of the genus has now been widely accepted. Dr. Weitzman is also responsible for describing five of the more recently introduced species, '' N. marilynae'', '' N. limatus'', '' N. nitidus'', '' N. britskii'' and '' N. anduzei''. Twenty species are now known, most of which are also familiar to aquarists. Several other unidentified ''Nannostomus'' species have been imported over the years; many were found as bycatch with other small characins, but their taxonomic status is yet to be determined.

Species

The 20 currently recognized species in this genus are: * '' Nannostomus anduzei''

Fernández Fernández () is a Spanish patronymic surname meaning "son of Fernando" of Germanic origin. The Germanic name Ferdinand that it derives from ( Gothic: ''Frið-nanð'') means "brave traveler." The Portuguese version of this surname is Fernandes ...

& S. H. Weitzman, 1987 * '' Nannostomus beckfordi'' Günther, 1872 (golden pencil fish) * '' Nannostomus bifasciatus'' Hoedeman, 1954 (two-lined pencil fish, whiteside pencil fish) * '' Nannostomus britskii'' S. H. Weitzman, 1978 (spot stripe pencil fish) * '' Nannostomus digrammus'' ( Fowler, 1913) (two-stripe pencil fish) * '' Nannostomus eques''

, 1876 (brown pencil fish, Diptail) * '' Nannostomus erythrurus'' ( C. H. Eigenmann, 1909) * '' Nannostomus espei'' ( Meinken, 1956) (Espe's pencil fish, barred pencil fish, brown pencil fish) * '' Nannostomus grandis'' Zarske, 2011 * '' Nannostomus harrisoni'' ( C. H. Eigenmann, 1909) (Harrison's pencil fish, black stripe pencil fish) * '' Nannostomus limatus'' S. H. Weitzman, 1978 (elegant pencil fish) * '' Nannostomus marginatus'' C. H. Eigenmann, 1909 (dwarf pencil fish) * '' Nannostomus marilynae'' S. H. Weitzman &

Cobb Cobb may refer to: People * Cobb (surname), a list of people and fictional characters with the surname Cobb * Cobb Rooney (1900–1973), American professional football running back Places New Zealand * Cobb River * Cobb Reservoir * Cobb Power ...

, 1975 (Marilyn's pencil fish, greenstripe pencil fish) * '' Nannostomus minimus'' C. H. Eigenmann, 1909 (least pencil fish) * '' Nannostomus mortenthaleri'' Paepke &

Arendt Hannah Arendt (born Johanna Arendt; 14 October 1906 – 4 December 1975) was a German and American historian and philosopher. She was one of the most influential political theorists of the twentieth century. Her works cover a broad ra ...

, 2001 (coral-red pencil fish) * '' Nannostomus nigrotaeniatus'' Zarske, 2013 * '' Nannostomus nitidus'' S. H. Weitzman, 1978 (shining pencil fish) * '' Nannostomus rubrocaudatus'' Zarske, 2009 (purple pencil fish) * '' Nannostomus trifasciatus''

, 1876 (three-stripe pencil fish) * '' Nannostomus unifasciatus''

, 1876 (one-line pencil fish)

Description

Most species are slender, pencil-shaped fish ranging in size from under ). ''N. marginatus'', ''N. rubrocaudatus'', and ''N. mortenthaleri'' possess shortened, blockier outlines reminiscent of pencil stubs. All but one species, ''Nannostomus espei'', possess one to five horizontal black or brown stripes with gold or silver iridescence appearing above the primary stripe. Most also display red, orange, or maroon highlights on their fins, and many have flashes of these colors on their bodies as well. The recently described ''N. mortenthaleri'' and ''N. rubrocaudatus'' are especially vividly colored. ''N. espei'' is unique in that the horizontal stripes are only weakly present and are supplanted by five dark comma-shaped blotches. Other species take this appearance at night, but only ''N. espei'' displays the pattern permanently and in daylight. The

adipose fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported only b ...

is present in some species and absent in others, while in certain species, such as ''N. eques'', its presence or absence varies between individuals. All species swim horizontally, except ''N. unifasciatus'' and ''N. eques'', which assume an oblique, 'snout-up' posture.

Sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

occurs in the genus to varying degrees. In some species the males are more brilliantly colored, especially the fins. In other species dimorphism is far less evident. However, the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

is generally a reliable indicator of gender. For most species the anal fin of adult males is enlarged and elongated (as in ''N. espei'', ''N. eques'', etc.) and/or more colorful (as in ''N. harrisoni'', ''N. marginatus,'' etc.). The popular aquarium species, ''N. trifasciatus'', is an exception in this regard.

Distribution

The genus as a whole has a vast distribution in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

, from

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

, and the

Guyanas The Guianas, also spelled Guyanas or Guayanas, are a geographical region in north-eastern South America. Strictly, the term refers to the three Guianas: Guyana, Suriname, and French Guiana, formerly British, Dutch, and French Guiana respectiv ...

in the north, to the southern

Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries ...

and

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

in the south, to

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

in the west, and

Belém Belém (; Portuguese for Bethlehem; initially called Nossa Senhora de Belém do Grão-Pará, in English Our Lady of Bethlehem of Great Pará), often called Belém of Pará, is the capital and largest city of the state of Pará in the north of B ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

, in the east. Several of the individual species have a distribution nearly as vast. As a result, many of the species are polymorphic and manifest marked color variations depending on the population. Over the years, some of these color variants have been erroneously described as separate species. Such names as 'Nannostomus ocellatus', 'N. anomalus' and 'N. auratus', among many others, are now known to be

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

s for the various species.

In the aquarium

To date, only two species, ''N. beckfordi'' and ''N. harrisoni'', have been commercially raised for the aquarium trade in fisheries, mostly in

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

. All of the remaining species that find their way to home aquaria are wild-caught from South American waters. ''Nannostomus'' species thrive in home aquaria when provided with soft, moderately acidic water, low nitrate levels, and temperatures in the range of . The addition of

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 ...

is recommended, including floating varieties as they reduce the likelihood of fish jumping, a common occurrence for some of the species, especially ''N. espei'' and ''N. unifasciatus''. They should be kept in

schools A school is the educational institution (and, in the case of in-person learning, the building) designed to provide learning environments for the teaching of students, usually under the direction of teachers. Most countries have systems of ...

of at least six, or in a

community aquarium Community aquaria are tanks that are designed to contain more than one species of fish. Most commonly they include a variety of species that do not normally occur together in nature, for example angelfish from Brazil, swordtails from Mexico, and ...

with other species of ''Nannostomus,'' other small peaceful

s, or

corydoras ''Corydoras'' is a genus of freshwater catfish in the family Callichthyidae and subfamily Corydoradinae. The species usually have more restricted areas of endemism than other callichthyids, but the area of distribution of the entire genus almos ...

. Aquariums with a strong water current, large tankmates, or swift-moving species should be avoided. If kept in a thickly planted single-species aquarium with the above water parameters, most species will spawn, eggs will not be eaten, and fry will be found growing in the floating plants. Baby

brine shrimp ''Artemia'' is a genus of aquatic crustaceans also known as brine shrimp or ''Sea-Monkeys, sea monkeys''. It is the only genus in the Family (biology), family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to t ...

, live or frozen, and other small-sized foods are required for both fry and adults. They are also avid

biofilm A biofilm is a Syntrophy, syntrophic Microbial consortium, community of microorganisms in which cell (biology), cells cell adhesion, stick to each other and often also to a surface. These adherent cells become embedded within a slimy ext ...

grazers and, for most of the species,

algae Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...

are under-reported staples of their diet. In most species, the males establish small territories and defend them. Their defensive actions are usually harmless, but in two species, ''N. mortenthaleri'' and ''N. trifasciatus'', antagonistic behavior directed at

conspecific Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species. Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organism ...

s can be harmful if sufficient space and plant cover is not provided. Once acclimated to the aquarium and provided with suitable conditions, they are hardy, often living for five or more years.

References

{{Authority control Lebiasinidae Fishkeeping Freshwater fish of South America Taxa named by Albert Günther