Rhinelepini is a

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

of fishes in the subfamily

Hypostominae The Hypostominae are a subfamily of catfishes of the family Loricariidae. Most members are restricted to tropical and subtropical South America, but there are also several species (in genera '' Ancistrus'', '' Chaetostoma'', '' Lasiancistrus'', ' ...

of the armored suckermouth catfish family

Loricariidae Loricariidae is the largest family (biology), family of catfish (order Siluriformes), with over 90 genus, genera and just over 680 species. Loricariids originate from freshwater habitats of Costa Rica, Panama, and tropical and subtropical South A ...

Taxonomy

This tribe is a well diagnosed

monophyletic In biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent co ...

group currently containing three

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

: '' Pogonopoma'', ''

Pseudorinelepis ''Pseudorinelepis genibarbis'' is a species of Loricariidae, armored catfish native to Brazil, Peru, and Ecuador where it is found in the Amazon basin. Taxonomy ''Pseudorinelepis'' is one of three genera contained in the tribe (biology), tribe R ...

'', and '' Rhinelepis''. When the tribe was first described, ''Pogonopomoides'' was a valid genus, but it is now a

synonym A synonym is a word, morpheme, or phrase that means precisely or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are a ...

of ''Pogonopoma''. ''Pseudorinelepis'' is the most basal, and ''Rhinelepis'' and ''Pogonopoma'' are more derived

sister groups In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

Appearance and anatomy

Rhinelepini species are generally medium to large-sized Loricariids. Rhinelepini species are unique among Loricariidae for having a normal, circular

iris Iris most often refers to: *Iris (anatomy), part of the eye * Iris (color), an ambiguous color term *Iris (mythology), a Greek goddess * ''Iris'' (plant), a genus of flowering plants * Iris (given name), a feminine given name, and a list of peopl ...

as opposed to the bilobed, omega iris. These species end to have relatively thick armor plates on their bodies. In

Iquitos Iquitos (; ) is the capital city of Peru's Maynas Province, Peru, Maynas Province and Loreto Region. It is the largest metropolis in the Peruvian Amazon, east of the Andes, as well as the List of cities in Peru, ninth-most populous city in Peru ...

Peru Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the south and west by the Pac ...

, '' Pseudorinelepis genibarbis'' is known as ''carachama sin costilla'', which actually means "Loricariid without ribs"; this refers to the trait that it shares with other Rhinelepini catfish; members of this tribe do not have ribs past the sixth vertebra. One of the characters that binds this group together is a large U-shaped

diverticulum In medicine or biology, a diverticulum is an outpouching of a hollow (or a fluid-filled) structure in the body. Depending upon which layers of the structure are involved, diverticula are described as being either true or false. In medicine, t ...

of the digestive tract; this is always filled with air. The first part of the diverticulum is modified from the

esophagus The esophagus (American English), oesophagus (British English), or œsophagus (Œ, archaic spelling) (American and British English spelling differences#ae and oe, see spelling difference) all ; : ((o)e)(œ)sophagi or ((o)e)(œ)sophaguses), c ...

and consists of thick musculature; this passes a short distance before reaching the second, main, U-shaped part of the diverticulum. In ''Rhinelepis'' and ''Pseudorinelepis'', the diverticulum functions as an accessory respiratory organ. In ''Rhinelepis'', the diverticulum is more attached to the abdominal wall and the interior of the diverticulum is more textured. In ''Pogonopoma'', the diverticulum is similar to a

swim bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ (anatomy), organ in bony fish that functions to modulate buoyancy, and thus allowing the fish to stay at desired water depth without having to maintain lift ...

and may be used as a hydrostatic organ; the first part of the diverticulum is greatly reduced and the second part is larger and has a smooth interior surface and less vascularized.

Distribution

The tribe Rhinelepini has an interesting

biogeography Biogeography is the study of the species distribution, distribution of species and ecosystems in geography, geographic space and through evolutionary history of life, geological time. Organisms and biological community (ecology), communities o ...

and reveal information about the aquatic systems of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. There is a split between the species that inhabit

Amazon Amazon most often refers to: * Amazon River, in South America * Amazon rainforest, a rainforest covering most of the Amazon basin * Amazon (company), an American multinational technology company * Amazons, a tribe of female warriors in Greek myth ...

and those that inhabit the eastern river systems. ''Pseudorinelepis'', the most basal group, is found only in the Amazon basin. ''Pogonopoma'', is found in the Mucuri,

Paraíba do Sul The Paraíba do Sul (), or simply Paraíba, is a river in southeast Brazil. It flows west to northeast from its farthest source at the source of the river Paraitinga to the sea near Campos dos Goytacazes. The river receives its name when it m ...

, and

Uruguay River The Uruguay River ( ; ) is a major river in South America. It flows from north to south and forms parts of the boundaries of Brazil, Argentina and Uruguay, separating some of the Argentine provinces of La Mesopotamia from the other two countr ...

systems in southeastern

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 ...

. ''Rhinelepis'' is found in

São Francisco River The São Francisco River (, ) is a large Rivers of Brazil, river in Brazil. With a length of , it is the longest river that runs entirely in Brazilian territory, and the fourth longest in South America and overall in Brazil (after the Amazon R ...

and

Paraná River The Paraná River ( ; ; ) is a river in south-central South America, running through Brazil, Paraguay, and Argentina for some ."Parana River". Encyclopædia Britannica. Encyclopædia Britannica Online. Encyclopædia Britannica Inc., 2012. Web. ...

. It is also thought to have spread through to the Paraíba by a sharing of its headwaters with the Paraná in the past, which eventually got separated into two basins. The oldest group, ''Pseudorinelepis'', inhabits the Amazon area, while the distribution of the newer, more derived groups occurs in Southern Brazil, which is comparatively older.

References

External links

* - Contains excerpts from the paper about the Rhinelepis group {{Taxonbar, from=Q2148100 Hypostominae Fish of South America Taxa named by Jonathan W. Armbruster