''Bryconops durbinae'', sometimes listed under the name ''Bryconops durbini'', is a small species of freshwater fish in the family

Iguanodectidae Iguanodectidae is a family of freshwater fish in the order Characiformes that lives in South America. It contains three genera: ''Iguanodectes, Piabucus'', and ''Bryconops''. Several species in the family, such as the green line lizard tetra (' ...

. It is the smallest species 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 species ...

'', and is

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the Tapajós river basin in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

Description

''Bryconops durbinae'' is small and slender, with a large mouth in comparison to the body. It is the smallest member of the genus ''

'' at 3.1 cm (1.2 in) in standard length; the second-smallest is '' Bryconops disruptus'', at 6.4 cm (2.5 in). Its fins are generally

hyaline A hyaline substance is one with a glassy appearance. The word is derived from , and . Histopathology Hyaline cartilage is named after its glassy appearance on fresh gross pathology. On light microscopy of H&E stained slides, the extracellula ...

(transparent), though it does bear a caudal ocellus (eyespot on the tail) that is transparent when preserved in alcohol, but ranges from red to yellow in life. Its caudal fin is darker than the rest, which makes said ocellus more obvious upon examination. In terms of body coloration, ''Bryconops durbinae'' is generally an

iridescent Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear gradually to change colour as the angle of view or the angle of illumination changes. Iridescence is caused by wave interference of light in microstruc ...

silver, with a black lateral stripe down each side underlined by a silver stripe. The

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 epithelia ...

, however, is regularly incomplete; this is a similarity it shares with congener '' Bryconops disruptus''. They are relatively easy to tell apart because the lateral line of ''B. disruptus'' has fewer pored scales, ranging wildly from 9 to 23, whereas ''B. durbinae'' has around 30 pored lateral line scales at a minimum. Reportedly, the small size and incomplete lateral line give ''Bryconops durbinae'' an incredibly similar appearance to the juveniles of congener '' Bryconops caudomaculatus''. One of the only ways to tell the two apart is that juvenile specimens of ''B. caudomaculatus'' have not developed teeth on their maxillaries. This is in contrast to adult specimens of ''B. durbinae'', which have maxillaries equipped with at least two teeth on each side, the outer set multicuspid and the inner set conical.

Taxonomy

When first described by German-American ichthyologist

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

in 1908, ''Bryconops durbinae'' was named ''Brycochandus durbini''. This established ''Brycochandus'' as a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

genus, but ''Brycochandus'' was later synonymized with ''Bryconops''. Knöppel et al. noted ''B. durbinae's'' similarity to members of the genus ''Creatochanes'', which was also later synonymized with ''Bryconops'' (though now accepted as a

subgenus In biology, a subgenus ( 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 the ge ...

). There are two subgenera in the genus ''Bryconops'', ''Bryconops'' and ''Creatochanes''. ''Bryconops durbinae'' is one of eight species that belong to the subgenus ''Bryconops'', making its full scientific name ''Bryconops (Bryconops) durbinae''. Other members are species that all share notable visual similarities, including ''B. caudomaculatus'' and ''B. disruptus'' (both mentioned prior). Prior to 2011, ''Bryconops'' was considered a member of the family

Characidae Characidae, the characids, is a family of freshwater subtropical and tropical fish belonging to the order Characiformes. They are found throughout much of Central and South America, including such major waterways as the Amazon and Orinoco Riv ...

, but research in said year moved it to the family

, along with the genera ''

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 maxi ...

'' and '' Iguanodectes''.

Etymology

Though ''Bryconops durbinae'' is listed under that name by many authorities, and is referred to as such in most modern publications, it is also easily found under the name ''Bryconops durbini'', a spelling that more closely resembles its baisonym. The origin of the specific epithet in question is limnologist and environmental toxicologist

Marion Durbin Ellis Marion Durbin Ellis (October 25, 1887December 16, 1972) was an American ichthyologist and entomologist. She is credited with conducting the most comprehensive study to date of the '' Hemigrammus'' genus of fish of which she named nineteen taxa. ...

, a student of Eigenmann's. ''B. durbinae'' lacks an accepted common name, but "Durbin's tetra" has been suggested as an etymological result of the specific epithet.

Habitat and ecology

''Bryconops durbinae'' is known only from the Rio Tapajos in

. This has been the case since it was described. The Rio Tapajos is a somewhat acidic clearwater river, with a pH that ranges from 4.5 to 7.8. Most of the time, the water carries very little sediment. This preference for an acidic environment is something shared with various members of the genus ''Bryconops'', but several of them - like ''B. caudomaculatus'', ''B. disruptus'', and '' B. colaroja'' - are found in blackwater rather than clearwater habitats. '' Bryconops collettei'' is a congener that inhabits both black and clear waters.

Conservation status

''Bryconops durbinae'' has not been evaluated by the

IUCN The International Union for Conservation of Nature (IUCN) is an international organization working in the field of nature conservation and sustainable use of natural resources. Founded in 1948, IUCN has become the global authority on the status ...

. Nonetheless, it faces threats to its population, mostly in the form of human activity and environmental destruction (which is also the case for the species of ''Bryconops'' that have been evaluated). The Rio Tapajos has long been considered for possible infrastructure development and mining operations, and there have been instances of illegal mining disturbing enough sediment to turn the water completely brown. The region is of great importance to not only ecological biodiversity but also to a population of roughly 1.4 million people, including various indigenous tribes, and so legal plans and operations have been reconsidered in the context of having as little impact on the region as possible. Therefore, ''Bryconops durbinae'' (alongside the other Tapajos-endemic species) has a greater chance for survival.

References

{{Taxonbar, from=Q6417078 Fish described in 1908 Bryconops Freshwater fish of Brazil Endemic fish of Brazil Fish of the Amazon basin Taxa named by Carl H. Eigenmann