''Nannostomus unifasciatus'', (from the

Greek Greek may refer to: Greece 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 ...

: ''nanos'' = small, and the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power of the ...

''stomus'' = relating to the mouth; from the

: ''unifasciatus'' = one band), commonly known as the one-lined pencilfish, is a freshwater

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

fish Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of li ...

belonging to the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

'' Nannostomus'' in 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.: "Relationshi ...

family Lebiasinidae. They are popular in the

aquarium An aquarium (plural: ''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. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, aq ...

trade due to their small size, beautiful color pattern, unique swimming posture and relative hardiness."Exotic Aquarium Fishes" by Dr. William T. Innes, Innes Publishing Co, Philadelphia, 1935 With its long, pencil-shaped profile, its single jet black stripe reminiscent of the graphite core of a pencil, and its eraser-colored caudal fin, this is the species for which the popular name, 'pencilfish', was first coined in the 1920s, later to be applied to all the species of the genus ''Nannostomus''."Pencilfishes" by William Vorderwinkler, TFH Publications, Neptune, NJ, 1956"Poecilobrycon unifasciatus" by Dr. William T. Innes, "The Aquarium," November 1940. Innes Publishing Co, Philadelphia

Taxonomy and distribution

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 describ ...

first described the species in 1876, making it the second of what are now nineteen species in the genus to be described."Review of South American Characoid fishes of the Subtribe Nannostomina" by Dr. Stanley H. Weitzman, Smithsonian Press,1966"Population History of the Amazonian One-Lined Pencilfish" by M.J. Sistrom, N. L. Chao & L. B. Beheregaray, "Journal of Zoology," #278, The Zoological Society of London, 2009 The taxonomy for the entire genus was for many decades the subject of heated debate, resulting in numerous conflicting revisions, leaving the genus for long periods in a state which has been aptly described as 'chaotic.'"Aquarium encyclopedia of Tropical Freshwater Fish" by A. Van Den Nieuwenhuizen et al., Elsevier Publishing Co, Lausanne, 1978 ''N. unifasciatus'' was often at the center of this controversy and this for several reasons."A revision of the South American fishes of the Genus Nannostomus" by Dr. Stanley H. Weitzman and J. Stanley Cobb, Smithsonian Press,1975 ''N. unifasciatus'', is broadly distributed throughout the

Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its 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 of Bolivi ...

, in

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, the

Guiana Shield The Guiana Shield (french: Plateau des Guyanes, Bouclier guyanais; nl, Hoogland van Guyana, Guianaschild; pt, Planalto das Guianas, Escudo das Guianas; es, Escudo guayanés) is one of the three cratons of the South American Plate. It is a ...

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

, and northern

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

. As a result, the species is

polychromatic Polychrome is the "practice of decorating architectural elements, sculpture, etc., in a variety of colors." The term is used to refer to certain styles of architecture, pottery or sculpture in multiple colors. Ancient Egypt Colossal statue ...

with many geographic populations manifesting subtle differences in color pattern. Over the years, some of these color morphs have been erroneously described as separate species. Further taxonomic confusion arose when various authors erected other genera for ''Nannostomus unifasciatus'' and its congeners, ''

Nannostomus eques ''Nannostomus eques'', (from the Greek: ''nanos'' = small, and the Latin ''stomus'' = relating to the mouth; from the Latin: ''eques'' = horseman), commonly known as the diptail pencilfish or brown pencilfish, is a freshwater species of fish belo ...

'' and '' Nannostomus harrisoni''. Confounding the situation still further, Dutch naturalist, J. J. Hoedeman published a paper in ''The Amsterdam Naturalist'' in 1950 that put forth that ''N. unifasciatus'' and ''N. eques'' were one and the same species. Consensus was finally achieved when, in his seminal paper on the genus ''Nannostomus'' in 1975, Dr. Stanley H. Weitzman restored Steindachner's taxonomy and expanded upon it, reaffirming the status of ''N. unifasciatus'' and ''N. eques'' as distinct and individuated species, and placing ''N. unifasciatus'' and all of its congeners in one genus, ''Nannostomus''. As a result, 'Poecilobrycon ocellatus,' 'Nannobrycon unifasciatus,' and similar epithets formerly applied to the species, are now relegated to

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

s to ''N. unifasciatus''. A population of the species has also been discovered on the island of

Trinidad Trinidad is the larger and more populous of the two major islands of Trinidad and Tobago. The island lies off the northeastern coast of Venezuela and sits on the continental shelf of South America. It is often referred to as the southernmos ...

, but it is believed to have been introduced.

Habitat

''Nannostomus unifasciatus'' commonly inhabits slow-moving tributaries, small rivers, and swampy areas throughout its substantial range. Dense aquatic vegetation and/or submerged branches and leaf litter are most often present. They also congregate beneath

floating island A floating island is a mass of floating aquatic plants, mud, and peat ranging in thickness from several centimeters to a few meters. Floating islands are a common natural phenomenon that are found in many parts of the world. They exist less co ...

s. Water parameters invariably range from slightly acidic (pH 6.5) to strongly acidic (pH 4.0) with negligible hardness. Their congener, ''N. eques'', is often found associated with them nearby, along with numerous other species of small

Description

Though the one-lined pencilfish is a small fish, with adults not reaching more than 7 cm in length, it is nevertheless one of the largest species of ''Nannostomus''. It is a long slender species with a small terminal mouth, and an

adipose fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as s ...

. It has one black longitudinal stripe that runs the length of the body and onto the caudal fin. The single black stripe is bordered above by a thin metallic gold band. The caudal is colored variously depending on the geographic population. Most all forms have red or orange pigment of varying intensity in the lower quadrant of the caudal, ventral to the black stripe. In some especially colorful populations, the red pigment extends above the black stripe as well, as pictured above. The Guyanese population, as well as one form from Bolivia, manifest a well-defined caudal ocellus above the black stripe. The ventral and anal fins are usually tipped with an enamel blue-white. ''N. unifasicatus'' is one of two species of ''Nannostomus'', the other being ''

'', that postures itself at an oblique, snout-up angle. Because of this similarity, ''N. unifasciatus'' and ''N. eques'' have often been confused in aquarium literature, though they are colored entirely differently from each other. '' Nannostomus harrisoni'', another long, slender single-striped species, is also often confused with ''N. unifasciatus'' based on a similar profile and coloration, but ''N. harrisoni'' swims in a horizontal posture and possesses bright red adornments on its anal and ventral fins, absent in ''N. unifasciatus''.

Sexual dimorphism

Sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

in this species is typical of many species in the genus ''Nannostomus''. The anal fin of males is modified in shape in most populations, the male's fin being slightly elongated. It is the least evident in the Guyanese population. The white tips of the ventral and anal fins are invariably brighter and more prominent on males. Males are also usually slimmer in profile.

Diet

''Nannostomus unifasciatus'' is omnivorous and feeds primarily on

insect Insects (from Latin ') are pancrustacean 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 ...

s and small

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

s. It is also an avid

periphyton Periphyton is a complex mixture of algae, cyanobacteria, heterotrophic microbes, and detritus that is attached to submerged surfaces in most aquatic ecosystems. The related term Aufwuchs (German "surface growth" or "overgrowth") refers to the col ...

grazer, ingesting microorganisms as well as

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

."Freshwater Fishes of the World " by Dr. Gunther Sterba,Urania Verlag,1959

In the aquarium

Though it has gone through periodic episodes of scarcity in the aquarium trade,"Exotic Tropical Fishes" by Dr. Cliff Emmens, et al. TFH Publications, New Jersey, 1962 ''N. unifasciatus'' has long been considered a most desirable aquarium species, Dr.

William T. Innes William Thornton Innes III, L.H.D. (February 2, 1874 – February 27, 1969) was an American aquarist, author, photographer, printer and publisher. Innes was the author of numerous influential books and hundreds of articles about aquarium fish, aqua ...

describing them as possessing "a marked elegance" and manifesting "that indefinable something known as class" in 1935. It is an appropriate

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 ...

species, if tankmates are of similar size and demeanor, and will thrive if kept in soft, mildly acidic water, low nitrate levels, and at temperatures between 72F and 82F. Baby

brine shrimp ''Artemia'' is a genus of aquatic crustaceans also known as brine shrimp. It is the only genus in the family Artemiidae. The first historical record of the existence of ''Artemia'' dates back to the first half of the 10th century AD from Urmia La ...

and other small-sized foods are indicated."Breeding Coral Red Pencilfish and other Pencilfishes" by Dr. Stanley H. Weitzman and Marilyn Weitzman, "Tropical Fish Hobbyist", February, 2002 Males will establish and defend small territories. Unlike its congener, '' N. eques'', which prefers the upper strata of the aquarium, ''N. unifasciatus'' tends to congregate in the mid to lower reaches. This is the only species of ''Nannostomus'' in the aquarium trade for which there is no recorded account of a successful spawning in captivity to date, this despite it being a widely kept and much admired aquarium species since the 1920s. Two reports of purported successful spawnings in the 1950s, published in aquarium literature—one in the Belgian magazine, "''Notre Aquarium''," and the other in the American magazine, "''The Aquarium''"—involved misidentification of the species, the spawnings having occurred for ''N. eques'' and ''N. harrisoni'' respectively, not ''N. unifasciatus''.

References

{{Taxonbar, from=Q3757847 Lebiasinidae Fishkeeping Fish of Bolivia Freshwater fish of Brazil Freshwater fish of Colombia Fish of Venezuela Fish of Guyana Fish of Trinidad and Tobago Fish of the Amazon basin Fish described in 1876 Taxa named by Franz Steindachner