Pencil Fish
Encyclopedia
Nannostomus is a genus
of fish
belonging to the Lebiasinidae
family
of Characins. All of the species in this genus are known as Pencil Fish or Pencilfish, several of which have become popular aquarium
fish due to their attractive coloration, unique shape and interesting demeanor.
in 1872 with the type species
, Nannostomus beckfordi. In 1876, Steindachner described three more species, Nannostomus unifasciatus, Nannostomus eques (pictured below) and Nannostomus trifasciatus (pictured above). In 1909 Eigenmann
described Nannostomus marginatus and Nannostomus harrisoni. These first six species to be described have been popular with aquarists since the early twentieth century, in part due to enthusiastic articles written about them, and compelling photographs taken of them, 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 H. Weitzman 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 the description of five of the more recently introduced species, Nannostomus marilynae, Nannostomus limatus, Nannostomus nitidus, Nannostomus britskii and Nannostomus anduzei. Seventeen species are now known to science, all but one of which, Nannostomus britskii--which is only known from preserved specimens—are also known to aquarists. Several other unidentified Nannostomus have been imported over the years, many found as bycatch with other small characins, but their taxonomic status is yet to be determined.
in the genus, it being clearly evident in several species with males being more brilliantly colored, especially with regard to color present in the fins, and far less evident in other species. However, a reliable indicator of gender for most of the species rests in the anal fin of adult males which is enlarged and elongated (as in N. espei, N. eques et al.) and/or the anal fin of males is more colorful (as in N. harrisoni, N. marginatus et al.). The popular aquarium species, Nannostomus trifasciatus, is an exception in this regard.
, from Colombia
, Venezuela
and the Guyanas
in the north, to the southern Amazon basin
and Bolivia
in the south, to Peru
in the west and Belem
, Brazil
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', 'Nannostomus anomalus' and 'Nannostomus auratus', among many others, are now known to be junior synonyms to the various species. To date, only two species, Nannostomus beckfordi and Nannostomus harrisoni, have been commercially raised for the aquarium trade in fisheries, mostly in Asia
. All of the remaining species that find their way to home aquaria
are wild-caught from South American waters.
. Aquaria with strong water current, large tankmates, or swift-moving species are contraindicated. If kept in a thickly planted single-species aquarium with the above water parameters, most species will spawn, eggs will not be eaten, and the fry will be found among the floating plants. Baby brine shrimp
, live or frozen, and other small-sized foods are required for both fry and adults. Nannostomus are also avid biofilm
grazers and, for most of the species, algae
is an under-reported staple of their diet. In most species the males will 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 conspecifics can have deleterious results if sufficient space and plant cover are not provided. Once acclimated to the aquarium, and provided with conditions to their liking, Nannostomus are hardy and have a firm grasp on life, often living for five or more years.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate 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...
belonging to the Lebiasinidae
Lebiasinidae
The Lebiasinidae , are a family of freshwater fishes found in Costa Rica, Panama, and South America. They are usually small and are known as ornamental fishes in aquaria, including popular fishes such as the pencil fish and splashing tetra.Lebiasinids are small, cylindrical fish, ranging from to ...
family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
of Characins. All of the species in this genus are known as Pencil Fish or Pencilfish, several of which have become popular 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...
fish due to their attractive coloration, unique shape and interesting demeanor.
Taxonomy
The genus, Nannostomus, was first erected by GüntherAlbert C. L. G. Günther
Albert Karl Ludwig Gotthilf Günther FRS, also Albert Charles Lewis Gotthilf Günther , was a German-born British zoologist, ichthyologist, and herpetologist....
in 1872 with the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, Nannostomus beckfordi. In 1876, Steindachner described three more species, Nannostomus unifasciatus, Nannostomus eques (pictured below) and Nannostomus trifasciatus (pictured above). In 1909 Eigenmann
Eigenmann
Eigenmann may mean:* Carl H. Eigenmann , ichthyologist, husband of Rosa Eigenmann.* Rosa Smith Eigenmann , ichthyologist, wife of Carl Eigenmann....
described Nannostomus marginatus and Nannostomus harrisoni. These first six species to be described have been popular with aquarists since the early twentieth century, in part due to enthusiastic articles written about them, and compelling photographs taken of them, by William T. Innes
William T. Innes
William Thornton Innes III, L.H.D. was an American aquarist, author, photographer, printer and publisher. Innes was the author of numerous influential books and hundreds of articles about aquarium fish, aquatic plants and aquarium maintenance during the formative years of the aquarium hobby in...
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 H. Weitzman 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 the description of five of the more recently introduced species, Nannostomus marilynae, Nannostomus limatus, Nannostomus nitidus, Nannostomus britskii and Nannostomus anduzei. Seventeen species are now known to science, all but one of which, Nannostomus britskii--which is only known from preserved specimens—are also known to aquarists. Several other unidentified Nannostomus have been imported over the years, many found as bycatch with other small characins, but their taxonomic status is yet to be determined.
Description
Most species are slender, pencil-shaped fish ranging in size from under 1" to approximately 2" in length. N. marginatus, N. rubrocaudatus and N. mortenthaleri possess a shortened, blockier outline 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 dorsal to the primary stripe. Most also display red, orange or maroon highlights in their fins, and many have flashes of these colors on their flanks as well. The recently described species, N. mortenthaleri and N. rubrocaudatus, are especially vividly colored. For N. espei alone, horizontal stripes are only weakly present and are supplanted by five dark comma-shaped blotches. This pattern is assumed by other species at night, but only N. espei displays the pattern permanently and in daylight. The adipose fin is present in some species and absent in others, while in certain species, Nannostomus eques for example, it may be present or absent within the species. All swim in a horizontal attitude except Nannostomus unifasciatus and Nannostomus eques, which assume an oblique, 'snout-up' posture. There is a range of sexual dimorphismSexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in the genus, it being clearly evident in several species with males being more brilliantly colored, especially with regard to color present in the fins, and far less evident in other species. However, a reliable indicator of gender for most of the species rests in the anal fin of adult males which is enlarged and elongated (as in N. espei, N. eques et al.) and/or the anal fin of males is more colorful (as in N. harrisoni, N. marginatus et al.). The popular aquarium species, Nannostomus trifasciatus, is an exception in this regard.
Distribution
The genus has a vast distribution in South AmericaSouth America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
, from Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
, Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
and the Guyanas
Guyanas
Guyana is a country in South America.Guyana, Guayana, or Guiana may also refer to:*Guayana Esequiba, the territory of Guyana claimed by Venezuela*Guayana Region, an administrative region of Venezuela...
in the north, to the southern Amazon basin
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...
and Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
in the south, to Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
in the west and Belem
Belem
Belem or Belém may refer to:* Belém, capital city of the Brazilian state of Pará* Belem , a three-masted barque from France* Belém, Alagoas, a municipality located in the Brazilian state of Alagoas...
, Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
in the east. Several of the individual species have a distribution nearly as vast. As a result, many of the species are polymorphic
Polymorphism (biology)
Polymorphism in biology occurs when two or more clearly different phenotypes exist in the same population of a species — in other words, the occurrence of more than one form or morph...
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', 'Nannostomus anomalus' and 'Nannostomus auratus', among many others, are now known to be junior synonyms to the various species. To date, only two species, Nannostomus beckfordi and Nannostomus harrisoni, have been commercially raised for the aquarium trade in fisheries, mostly in Asia
Asia
Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and with approximately 3.879 billion people, it hosts 60% of the world's current human population...
. All of the remaining species that find their way to home aquaria
Aquaria
Aquaria may refer to:*Aquarium, in the plural*Aquaria , a computer game*Aquaria , a Brazilian metal band*Aquaria, one of the Twelve Colonies in Battlestar Galactica...
are wild-caught from South American waters.
In the aquarium
Nannostomus thrive in home aquaria when provided with soft, moderately acidic water, low nitrate levels and temperatures in the range of 72F to 82F. The addition of aquatic plants, including floating varieties, is recommended. The latter will reduce the likelihood of the fish jumping, which is a common occurrence for some of the species, especially N. espei and N. unifasciatus. They should be kept in schools of at least six. If kept in a community aquarium, the best tankmates are other species of Nannostomus, small peaceful characins and corydorasCorydoras
Members of the South American Corydoras genus are freshwater temperate and tropical catfish in the armored catfish family , and are commonly referred to as corydorases, cories, or cory catfish.-Taxonomy:...
. Aquaria with strong water current, large tankmates, or swift-moving species are contraindicated. If kept in a thickly planted single-species aquarium with the above water parameters, most species will spawn, eggs will not be eaten, and the fry will be found among the floating plants. Baby brine shrimp
Brine shrimp
Artemia is a genus of aquatic crustaceans known as brine shrimp. Artemia, the only genus in the family Artemiidae, has changed little externally since the Triassic period...
, live or frozen, and other small-sized foods are required for both fry and adults. Nannostomus are also avid biofilm
Biofilm
A biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
grazers and, for most of the species, algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
is an under-reported staple of their diet. In most species the males will 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 conspecifics can have deleterious results if sufficient space and plant cover are not provided. Once acclimated to the aquarium, and provided with conditions to their liking, Nannostomus are hardy and have a firm grasp on life, often living for five or more years.