''Bryconops imitator'' is a small freshwater fish that lives in the rivers 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 ...

. It is a small, silvery fish with a bright red tail fin that is known to eat invertebrates, like insects and freshwater zooplankton. It gets the specific epithet "imitator" from its strong resemblance to another member of the genus, ''

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

''; however, there are subtle differences in bone structure, color, and other traits that allow for differentiation. ''B. imitator'' and ''B. colaroja'' otherwise share many visual similarities that make them easy to confuse.

Description

''Bryconops imitator'' usually reaches 7.8 cm (3.1 in) in standard length. This places it close to the middle of the length range for '' Bryconops'' as a whole. Its scales are generally silver with a hint of emerald-green, and one of its most distinguishing features is a bright-red tail, a trait it only shares with ''B. colaroja'' (which was named for its tail; cola- means tail and -roja means red). The fact that ''B. imitator'' and ''B. colaroja'' are the only two members of ''Bryconops'' - and, in fact, two of very few tetras in general - to have this specific trait is one of the reasons that ''B. imitator'' went unrecognized as long as it did. Even upon a relatively close inspection, ''B. imitator'' is easy to confuse with ''B. colaroja'', but several differentiating facets exist. These involve features as subtle as where scales form new rows on the body; the rows of ''B. imitator's'' scales split at the seventh scale in the mid-dorsal scale row, but the rows of ''B. colaroja's'' scales split after the 5th and the 8th scale. Differences in body shape are easier to see. ''B. imitator'' has a slightly more arched predorsal region, and a thinner caudal peduncle (the joint where the tail fin attaches to the body). ''Bryconops imitator'' has several differences in coloration that set it apart from other related species, not just ''B. colaroja''. It lacks a

humeral spot Humeral spot (from Latin ''humerus'', pertaining to the shoulder) is a mark or pattern found on several species of fish, typically above the pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding f ...

, a mark above the pectoral fin in some fish (including many ''Bryconops''), and has no increase in pigmentation in the eye and cheek region. The lobes of its caudal (tail) fin are equal in length, and it lacks the caudal ocellus (eyespot) seen in plenty of its congeners. It also has no band of pigment at the base of its anal fin, and this specifically differentiates it from '' B. colanegra'', which has an exaggerated stripe on its anal fin base.

Taxonomy

''Bryconops imitator'' has been considered a member of ''Bryconops'' since its designation in 2002 by Chernoff & Machado-Allison. ''Bryconops'' consists of two

subgenera 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 ...

, ''Bryconops'' and ''Creatochanes'', and ''B. imitator'' is considered a member of ''Creatochanes''; hence, its full scientific name is ''Bryconops (Creatochanes) imitator''. Members of ''Creatochanes'' are classified based upon having at least one tooth, up to three, in both sides of the maxillary bone. While this cannot be quantified from external observation alone, the denticulation of the gill rakers (how many denticles, or toothlike protrusions, the gill rakers have) can also play a part in classification. ''B. imitator's'' gill rakers, while perhaps the least denticulated amongst comparable species, still bear the right similarities to place it in a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

within its subgenus; this clade consists of ''Bryconops melanurus, B. melanurus'', ''B. colaroja'', ''B. colanegra'', and ''B. imitator''.

Distribution and ecology

''Bryconops imitator'' is endemic to the Caura River, a

blackwater Blackwater or Black Water may refer to: Health and ecology * Blackwater (coal), liquid waste from coal preparation * Blackwater (waste), wastewater containing feces, urine, and flushwater from flush toilets * Blackwater fever, an acute kidney disea ...

tributary of the Orinoco river. It has a noted preference for sandy substrate (as opposed to rocky or clay-heavy). It demonstrates similar environmental needs to its cousin ''B. colaroja'', which contributed to their longtime synonymy, but ''B. colaroja'' is endemic to an entirely different tributary of a different river altogether (the Cuyuní river, which is a tributary of the Essequibo river). Though detailed research on its specific preferences is lacking, ''B. imitator'' is known to target invertebrates. The presence of gill rakers suggests that microscopic invertebrates are included, and the Caura River is not lacking. There is a plentiful population of

zooplankton Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek word for ''animal''). Plankton are aquatic organisms that are unable to swim effectively against currents, and consequently drift or are carried along by ...

that rises and falls with the yearly flood cycle, though these zooplankton do not reproduce in the river itself and are instead solely washed in from the

floodplains A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

or other channels.

Conservation status

The IUCN considers ''B. imitator'' to be a near-threatened species largely thanks to habitat loss and degradation. Illegal gold mining is a thriving industry in Latin America as a whole, and the activities therein are damaging and endangering many habitats, not just aquatic. Specific threats include mercury toxicity, which is dangerous not just to inhabitants like ''B. imitator'' but also to the human communities that rely on the river systems for water.

References

{{Taxonbar, from=Q5547360 Fish described in 2002 Bryconops Freshwater fish of Venezuela