''Bryconops colaroja'' is a small species of fish from the fresh waters of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

. The specific epithet "colaroja" means "red tailed", and it gets this name from its most distinctive feature - a deep red caudal fin, largely unique amongst members of its genus. It lives in tributaries and creeks that are a part of the Cuyuni river basin.

Description

''Bryconops colaroja'' is one of the smaller members of the genus ''

Bryconops ''Bryconops'' is a genus of freshwater fish in the family Iguanodectidae from South America. It consists of small fish, all under half-a-foot long, with slender bodies and silvery scales, though there is some mild color variation. Several specie ...

'', measuring around 7.8 cm (3.1 in) in

standard length Fish measurement is the measuring of individual fish and various parts of their anatomies. These data are used in many areas of ichthyology, including taxonomy and fisheries biology. Overall length * Standard length (SL) is the length of a fish m ...

. In general, the genus ''Bryconops'' has a similar body shape to sister genus ''

Piabucus ''Piabucus'' is a genus of freshwater tetras in the family Iguanodectidae. All three species are found in South America, largely the Amazon and its major tributaries. None of them are longer than half a foot long, with the largest reaching a max ...

'', described as resembling a

minnow Minnow is the common name for a number of species of small freshwater fish, belonging to several genera of the families Cyprinidae and Leuciscidae. They are also known in Ireland as pinkeens. Smaller fish in the subfamily Leusciscidae are co ...

smelt Smelt may refer to: * Smelting, chemical process * The common name of various fish: ** Smelt (fish), a family of small fish, Osmeridae ** Australian smelt in the family Retropinnidae and species ''Retropinna semoni'' ** Big-scale sand smelt ''At ...

. "THE FISH FAMILIES". Field Guide to the Fishes of the Amazon, Orinoco, and Guianas, edited by Peter van der Sleen and James S. Albert, Princeton: Princeton University Press, 2017, pp. 95-96. https://doi.org/10.1515/9781400888801-009 Its scales are mostly greenish-silver, slightly darker on the back than on the rest of the body. The uniform gradient of the scales, lacking prominent markings, is a feature that can be used to differentiate it from other members of the genus; for example, ''B. colanegra'' and '' B. melanurus'' have distinct blotches of pigmentation in the cheek and eye region. ''Bryconops colaroja'' is the only member of the genus ''Bryconops'' to have a caudal fin that is completely red, aside from congener '' Bryconops imitator'' (which gets its name from its similarity to ''B. colaroja''). The margins of the fin rays are the only places where

melanophores Chromatophores are cells that produce color, of which many types are pigment-containing cells, or groups of cells, found in a wide range of animals including amphibians, fish, reptiles, crustaceans and cephalopods. Mammals and birds, in contrast, ...

are present, making dark lines radiate inwards from the fin margin. This distinct color is the origin of the fish's scientific name; "cola" means "tail", and "roja" means "red". It is sometimes called the redtailed bryconops because of this, but this is not in wide use, and ''B. colaroja'' has no accepted common name. Though ''Bryconops colaroja'' has

gill rakers Gill rakers in fish are bony or cartilaginous processes that project from the branchial arch (gill arch) and are involved with suspension feeding tiny prey. They are not to be confused with the gill filaments that compose the fleshy part of the ...

that are notably denticulated - that is, adorned with toothlike protrusions - its congener ''B. colanegra'' is known to have gill rakers with higher denticulation. The teeth are multicuspid, which is a feature that the ''Bryconops'' clade shares with sister clade

Iguanodectinae Iguanodectinae is a subfamily of small freshwater fish in the family Iguanodectidae. They are most prominently found in the Amazon river basin and its major tributaries, but they are also known from the Tocantins, Orinoco, and Paraguay rivers. ...

Taxonomy

''Bryconops colaroja'' was described in 1999 as a part of the

subgenus In biology, a subgenus (plural: subgenera) is a taxonomic rank directly below genus. In the International Code of Zoological Nomenclature, a subgeneric name can be used independently or included in a species name, in parentheses, placed between t ...

''Creatochanes'', making its full name ''Bryconops (Creatochanes) colaroja''. It has no synonyms, nor is it often mistaken for its congeners, aside from ''B. imitator''. The red tail makes it fairly easy to identify. ''Bryconops colaroja'', as with all members of the genus ''Bryconops'', was once considered a part of the family

Characidae Characidae, the characids or characins is a family of freshwater subtropical and tropical fish, belonging to the order Characiformes. The name "characins" is the historical one, but scientists today tend to prefer "characids" to reflect their st ...

, and is still listed there by some sources. However, research in 2011 by Oliveira et al. moved the genera ''Bryconops'', ''

Iguanodectes ''Iguanodectes'' is a genus of freshwater fish found in tropical South America, with eight currently described species. They are all small tetras, none longer than 5 inches, and often have attractive silvery or striped scales, which makes them a t ...

'', and ''

'' to the family

Iguanodectidae Iguanodectidae is a family of freshwater fish in the order Characiformes that lives in South America. It is home to the subfamily Iguanodectinae (Eigenmann, 1909) and the monotypic ''Bryconops'' clade. Several species in the family, such as the ...

, Oliveira, C., Avelino, G.S., Abe, K.T. et al. ()26 September 2011). Phylogenetic relationships within the speciose family Characidae (Teleostei: Ostariophysi: Characiformes) based on multilocus analysis and extensive ingroup sampling. ''BMC Evol Biol''. 11(275). https://doi.org/10.1186/1471-2148-11-275. Retrieved 10 April 2022. which is where ''B. colaroja'' currently stands.

Habitat and ecology

''Bryconops colaroja'' is known only from the Cuyuní river basin, leaning on the border between

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

Guyana Guyana ( or ), officially the Cooperative Republic of Guyana, is a country on the northern mainland of South America. Guyana is an indigenous word which means "Land of Many Waters". The capital city is Georgetown. Guyana is bordered by the ...

; however, it has not been collected from the Cuyuni river main, only smaller creeks and tributaries. It demonstrates a preference for slightly acidic waters, as well as a rocky or sandy substrate.Echevarría, G. 2019. ''Bryconops colaroja''. The IUCN Red List of Threatened Species 2019: e.T118038882A118038887. https://dx.doi.org/10.2305/IUCN.UK.2019-3.RLTS.T118038882A118038887.en. Accessed on 23 April 2022. The blackwater nature of ''B. colaroja's'' habitat indicates that it does not need well-oxygenated waters to survive. Part of what characterizes a blackwater river is a high concentration of

humic substances Humic substances (HS) are organic compounds that are important components of humus, the major organic fraction of soil, peat, and coal (and also a constituent of many upland streams, dystrophic lakes, and ocean water). For a long era in the 19th ...

, which are the result of

microbial A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

activity. This microbial activity consumes much of the oxygen in the water, and as such fish with high-oxygen needs are not suited for blackwater environments.

Diet

The diet of ''Bryconops colaroja'' hasn't been the subject of extensive study on its own, but other members of the genus are known to be largely

insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores were ...

, and have noted preferences for invertebrates of various origins. The

orangefin tetra The orangefin tetra (''Bryconops affinis'') is a small species of freshwater fish from South America that belongs to the family Iguanodectidae. Though common in its native range, it seems to prefer fast-flowing and shallow creeks. It is an active ...

(''B. affinis'') makes plants a more prominent part of its diet, though it still eats invertebrates. The

tailspot tetra The tailspot tetra (''Bryconops caudomaculatus'') is a freshwater fish that lives in the coastal river regions of upper South America. Both its common and scientific names reference the distinct spot of color present on the tail fin, which is one ...

(''B. caudomaculatus'') jumps out of the water to catch flying insects, and '' B. alburnoides'' demonstrates a taste for terrestrial insects. Based on the most current information, ''B. colaroja'' can reasonably be assumed to be an insectivore that takes supplemental plant material.

Conservation status

Though little is known of ''B. colaroja's'' population trends, it is considered a species of least concern by the

IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

. A potential threat is that the Cuyuni river main is regularly threatened by mining activity; the waters have been disturbed and riverbanks destroyed in the past, as it is a source of

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile met ...

. The Cuyuni river is generally in poor health, which places ''B. colaroja'' (as well as the other native species) at an increased risk of endangerment. However, its presence has been noted by mining operations in the past, which in turn has increased their willingness to take precautions to protect it.

References

{{Taxonbar, from=Q5517930 Fish described in 1999 Characiformes Fish of South America