''Bryconops gracilis'' is a small species of freshwater fish from 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 one of multiple species for which the common name "lambari" is used. Though not well-studied, it has been re-described in recent years in order to differentiate it from ''Bryconops alburnoides'', a congener to which it bears a strong resemblance.

Description

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

of ''Bryconops gracilis'' - the very first collected specimen - was reported at 7.5 cm (2.9 in) in SL (standard length, with the length of the tail fin excluded). Further specimens of ''B. gracilis'' range from 6.1 to 12.3 cm (2.4 to 4.8 in) SL. Like the rest of ''Bryconops'', ''B. gracilis'' has a slender body reminiscent of a minnow's."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 body is also on the shallower side when compared to other members of its genus, a feature it shares with '' B. alburnoides'', '' B. collettei'', and '' B. magoi''. ''Bryconops gracilis'' is frequently confused with congener ''

Bryconops alburnoides ''Bryconops alburnoides'' is a small freshwater fish, approximately 6 inches long at its largest, that lives in the rivers of South America. It has a slender body, with a yellowish dorsal fin and yellow-tinged back scales that fade into silver on ...

'', the type species of the genus. This is because they share several morphological traits, such as a yellowish caudal fin, high number of

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

scales, and overall elongated body shape. Both ''B. gracilis'' and ''B. alburnoides'' have 54 to 62 pored lateral line scales. Early descriptions also drew comparisons to '' Bryconops melanurus'' (then called ''Creatochanes melanurus'') due to morphological overlap.

Taxonomy

When it was originally described by German-American ichthyologist

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

in 1908, B. gracilis was named ''Creatochanes gracilis''. It is still occasionally referenced under that name. Eigenmann's original nomenclature retains an element of validity in the current day. This is because there are two subgenera in ''Bryconops'', ''Bryconops'' and ''Creatochanes'', and the latter draws from Eigenmann's work. However, ''B. gracilis'' belongs to the subgenus ''Bryconops'', making its full name ''Bryconops (Bryconops) gracilis''. It shares this subgenus with congener ''B. alburnoides'', with which it has been confused in the past, but similar congener ''B. melanurus'' is in ''Creatochanes''. ''Bryconops gracilis'' is an iguanodectid (part of 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 ...

). This is a fairly recent classification, and was prompted by a review 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 ...

in 2011 wherein the genera ''

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 ...

'', ''

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 ...

'', and ''

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 ...

'' were all moved from Characidae to Iguanodectidae. Some sources still list ''B. gracilis'' as a characin.

Etymology

The specific epithet ''gracilis'' means "slender" (note the similarity to the word "graceful"), and is in reference to the narrow, elongated body. It shares this specific epithet with multiple other species, such as ''Hemiodus gracilis'' and ''Pseudanos gracilis''.Prang, Gregory. (2007)
An industry analysis of the freshwater ornamental fishery with particular reference to the supply of Brazilian freshwater ornamentals to the UK market
Uakari. 3. 10.31420/uakari.v3i1.18. In terms of a common name, ''B. gracilis'' is sometimes called the "lambari", but this is a name that also applies to other small species of fish in nearby regions. These fish include ''Astyanax altiparanae'', ''Bryconamericus lambari'', and ''Deuterodon iguape''. Otherwise, ''B. gracilis'' has no accepted common name.

Distribution and conservation

''Bryconops gracilis'' is native to

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 ...

, found only in the Tapajos river basin. Three of its congeners have also been described therein: '' B. durbinae'', '' B. munduruku'', and '' B. transitoria''. Though ''B. gracilis'' is currently listed as least concern by the International Union for the Conservation of Nature (IUCN), the Tapajos river is under constant threat of human impact. The water is sometimes so full of sediments kicked up by illegal mining that entire portions of the river turn entirely brown. Factors like this place ''B. gracilis'', as well as other species endemic to the area, under greater survival pressure.

References

{{Taxonbar, from=Q5665320 Fish described in 1908 Characiformes Fish of South America Taxa named by Carl H. Eigenmann