''Cetopsis'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...

es (

order Order, ORDER or Orders may refer to: * A socio-political or established or existing order, e.g. World order, Ancien Regime, Pax Britannica * Categorization, the process in which ideas and objects are recognized, differentiated, and understood ...

Siluriformes) of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Cetopsidae The Cetopsidae are a small family of catfishes (order Siluriformes), commonly called the whale catfishes. Taxonomy This family contains five genera divided into two subfamilies, Cetopsinae and Helogeneinae. Helogeneinae was previously a family-l ...

Taxonomy

''Cetopsis'' is one of four genera in the subfamily Cetopsinae within the family Cetopsidae. ''Cetopsis'' is greatly expanded from when it only included ''C. coecutiens''. A number of genera were synonymized with ''Cetopsis'' to retain

monophyly 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 comm ...

of cetopsine genera without erecting many new ones. Information on some species is limited due to lack of specimens. ''C. caiapo'', ''C. jurubidae'', ''C. sarcodes'', and ''C. umbrosa'' are only known from a single specimen each, ''C. starnesi'' is only known from two specimens, ''C. parma'' is only known from four, and ''C. sandrae'' from only six specimens.

Distribution

''Cetopsis'' species are found in major freshwater rivers draining to the east and west 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 ...

, including the

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 ...

, Atrato,

Madeira Madeira ( ; ), officially the Autonomous Region of Madeira (), is an autonomous Regions of Portugal, autonomous region of Portugal. It is an archipelago situated in the North Atlantic Ocean, in the region of Macaronesia, just under north of ...

, Magdalena,

Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers approximately 1 million km2, with 65% of it in Venezuela and 35% in Colombia. It is the List of rivers by discharge, f ...

Tocantins Tocantins () is one of the 26 states of Brazil. It is the newest state, formed in 1988 and encompassing what had formerly been the northern two-fifths of the state of Goiás. Tocantins covers and had an estimated population of 1,496,880 in 2014 ...

, and other rivers in

Bolivia Bolivia, officially the Plurinational State of Bolivia, is a landlocked country located in central South America. The country features diverse geography, including vast Amazonian plains, tropical lowlands, mountains, the Gran Chaco Province, w ...

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 ...

Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...

Ecuador Ecuador, officially the Republic of Ecuador, is a country in northwestern South America, bordered by Colombia on the north, Peru on the east and south, and the Pacific Ocean on the west. It also includes the Galápagos Province which contain ...

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 ...

, and

Venezuela Venezuela, officially the Bolivarian Republic of Venezuela, is a country on the northern coast of South America, consisting of a continental landmass and many Federal Dependencies of Venezuela, islands and islets in the Caribbean Sea. It com ...

Description

''Cetopsis'' is distinguished from the other genera in the Cetopsinae from the combination of the absence of a spinelet associated with the

dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...

, the absence of spines on the dorsal and

pectoral fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish aquatic locomotion, swim. Apart from the tail or caudal fin, fish fins have no direct connection with the vertebral column ...

s, and the possession of a single row of teeth on the

vomer The vomer (; ) is one of the unpaired facial bones of the skull. It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones. The vomer forms ...

. Like most other members of the subfamily Cetopsinae, mature males in most species have the distal ends of the first rays of the dorsal and pectoral fins elongated into filaments and a convex (vs. straight) margin to the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

. Unlike all other species, in ''C. coecutiens'', the fin ray filaments are present in both sexes and this species must be differentiated by the anal fin. In ''C. oliveirai'', the fin ray filaments are much longer than in other species, however there is also no difference between the sexes in either the fin ray filament lengths or the anal fin margin. The presence of these traits in mature males cannot be confirmed in ''C. amphiloxa'', ''C. caiapo'', ''C. jurubidae'', ''C. parma'', due to the small number of specimens. The one specimen of ''C. sarcodes'' is probably an immature male based on the form of its

genital papilla The genital papilla is an anatomical feature of the external genitalia of some animals. In mammals In mammals, the genital papilla is a part of the vulva not present in humans, which appears as a small, fleshy flab of tissue. The papilla covers the ...

, though it lacks the fin ray elongations and convex anal fin margin of mature males. Colour patterns vary between species. ''C. amphiloxa'' has very small spots on the dorsal and lateral surfaces of the body, while ''C. montana'', ''C. plumbea'', ''C. starnesi'', and ''C. umbrosa'' have eye-sized spots on the lateral surfaces of the body. ''C. arcana'', ''C. caiapo'', ''C. orinoco'', ''C. parma'', ''C. sarcodes'' have a dark humeral spot (a spot in the shoulder region). ''C. arcana'', ''C. montana'', ''C. pearsoni'', ''C. sandrae'', ''C. starnesi'', and ''C. umbrosa'' have a posteriorly rounded, variably developed, bilobed patch of dark pigmentation at the base of the caudal fin. ''C. fimbriata'' have a band of dark pigmentation along the distal portions of the anal fin. ''C. motatanensis'' has a caudal fin darkly pigmented throughout other than for a narrow pale distal margin, while ''C. orinoco'' has dark pigmentation on the caudal fin particularly on the distal portions of the fin. The body of ''Cetopsis'' species ranges from slender to stout. Unlike all other species, ''C. candiru'' has incisiform (vs. conical) teeth on the

and

dentary In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone ...

, and also has a more slender body than all other species. Unlike all other species, ''C. coecutiens'' has transverse, slit-like posterior nares rather than rounded posterior nares. The eye is completely absent in ''C. oliveirai''; the eye, present to some degree in all other species of ''Cetopsis'', is situated on the lateral surface of the head and is visible from above but not below. In most species, the mouth is inferior and the width is one-half the length of the head; the margin of the lower jaw is often gently to broadly rounded. The mental

barbels In fish anatomy and turtle anatomy, a barbel is a slender, whisker like sensory organ near the mouth (sometimes called whiskers or tendrils). Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the z ...

are almost always approximately the same size and length to each other and often the same length as or sometimes shorter than the slender and short maxillary barbels. In most species, the dorsal fin is moderately large, but in ''C. caiapo'' and ''C. parma'', it is relatively small. The caudal fin is shallowly to deeply forked and symmetrical (though apparently asymmetrical in ''C. jurubidae''), the ends of the lobes usually pointed, bluntly pointed, or rounded (however, the tips are damaged in the single specimen of ''C. umbrosa''). The base of the anal fin is moderate to long, though is relatively short in some species. The pelvic fin ranges from short to moderate to large. The pectoral fin length is usually two-thirds of the length of the head. ''C. oliveirai'' has been found to be a

paedomorphic Neoteny (), also called juvenilization,Montagu, A. (1989). Growing Young. Bergin & Garvey: CT. is the delaying or slowing of the physiological, or somatic, development of an organism, typically an animal. Neoteny in modern humans is more signi ...

species of the genus ''Cetopsis'', with many traits similar to juveniles of ''C. coecutiens''.

Ecology

''C. arcana'' was collected in a

karstic Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. There is some eviden ...

region of the upper Tocantins River basin in both epigean (above-ground) and subterranean waters. ''C. baudoensis'' has been found in a highly turbid, white-water river over clay bottoms with logs in the main channel and clay and leaves in the lower portions of the quebradas that were tributary to the main river channel. Specimens were collected at depths of 2 m or less and at an elevation of less than 50 m. ''C. motatanensis'' is found in swiftly flowing water among rubble to coarse gravel. ''C. oliveirai'' originates in white water systems at depths of 2–40 m and feeds on terrestrial

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s. ''C. orinoco'' reportedly inhabits the middle portions of the water column of high-velocity streams during the night and hides among submerged branches and other obstructions in the river channel during the day. ''C. plumbea'' is reported to feed on a variety of terrestrial and aquatic

insect Insects (from Latin ') are Hexapoda, hexapod invertebrates of the class (biology), class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (Insect morphology#Head, head, ...

s. It inhabits streams with moderate current and a depth of up to 1 m, occurring within such streams in areas over sand substrates but lacking vegetation. ''C. sandrae'' was found in riffles in a relatively fast-flowing forest stream, approximately 3–4 m wide and 0.4–0.8 m deep with a small waterfall. ''C. candiru'', commonly known as the Candiru-açu, is perhaps the most formidable species, being a hunter and scavenger of dead and dying fish, which it devours from the inside-out using its circular maw of razor-sharp teeth. Featured heavily in

River Monsters ''River Monsters'' is a British wildlife Documentary film, documentary television series produced for Animal Planet by Icon Films of Bristol, United Kingdom. It is hosted by Angling, angler and biologist Jeremy Wade, who travels around the gl ...

and

BBC The British Broadcasting Corporation (BBC) is a British public service broadcaster headquartered at Broadcasting House in London, England. Originally established in 1922 as the British Broadcasting Company, it evolved into its current sta ...

's "Amazon Abyss", it has been implicated and proven to attack and devour humans, with corpses containing hundreds of fish being recorded in morgues. It is worth noting however that humans only become prey of ''C. candiru'' when dead or incapacitated, such as when drowned or drunk.

Species

There are currently 21 recognized species in this genus: * '' Cetopsis amphiloxa'' ( C. H. Eigenmann, 1914) * '' Cetopsis arcana''

Vari Vari () is a southern suburb of Athens and former municipality in East Attica, Greece along the Athens coast. The ancient Athenian deme of Anagyrous was situated here. Since the 2011 local government reform it is part of the municipality Vari-Vo ...

Ferraris Ferrari S.p.A. (; ) is an Italian luxury sports car manufacturer based in Maranello. Founded in 1939 by Enzo Ferrari (1898–1988), the company built Auto Avio Costruzioni 815, its first car in 1940, adopted its current name in 1945, and be ...

de Pinna De Pinna was a high-end clothier for men and women founded in New York City in 1885, by Alfred De Pinna (1831–1915), a Sephardic Jew born in England. They also sold menswear-inspired clothing for women that was finely tailored. The flagship sto ...

, 2005 * '' Cetopsis baudoensis'' ( Dahl, 1960) * '' Cetopsis caiapo''

, 2005 * ''

Cetopsis candiru ''Cetopsis candiru'', also known as candiru, candiru açú, candiru cobra or canero, is a carnivorous species of whale catfish found in the Amazon basin of Peru, Brazil and Bolivia. Similar to ''Cetopsis coecutiens'', ''Cetopsis candiru'' is a ...

Spix Johann Baptist Ritter von Spix (9 February 1781 – 13 March 1826) was a German natural history, biologist. From his expedition to Brazil, he brought to Germany a large variety of specimens of plants, insects, mammals, birds, amphibians and fish. ...

Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he recei ...

, 1829 * ''

Cetopsis coecutiens ''Cetopsis coecutiens'', the ''candiru-açú'', ''piracatinga'', ''bagre ciego'' (Literal translation, lit. blind catfish), or the blue whale catfish, is a species of catfish found throughout the Amazon basin in Bolivia, Brazil, Colombia, Peru an ...

'' ( M. H. C. Lichtenstein, 1819) * '' Cetopsis fimbriata''

, 2005 * '' Cetopsis gobioides'' Kner, 1858 * '' Cetopsis jurubidae'' ( Fowler, 1944) * '' Cetopsis montana''

, 2005 * '' Cetopsis motatanensis'' ( L. P. Schultz, 1944) * '' Cetopsis oliveirai'' ( Lundberg & Rapp Py-Daniel, 1994) * '' Cetopsis orinoco'' ( L. P. Schultz, 1944) * ''

Cetopsis othonops ''Cetopsis'' is a genus of catfishes (order (biology), order Siluriformes) of the family (biology), family Cetopsidae. Taxonomy ''Cetopsis'' is one of four genera in the subfamily Cetopsinae within the family Cetopsidae. ''Cetopsis'' is greatly ...

'' ( C. H. Eigenmann, 1912) * '' Cetopsis parma'' J. C. de Oliveira,

, 2001 * '' Cetopsis pearsoni''

, 2005 * '' Cetopsis plumbea''

Steindachner Franz Steindachner (11 November 1834 in Vienna – 10 December 1919 in Vienna) was an Austrian zoologist, ichthyologist, and herpetologist. He published over 200 papers on fishes and over 50 papers on reptiles and amphibians. Steindachner descri ...

, 1882 * '' Cetopsis sandrae''

, 2005 * '' Cetopsis sarcodes''

, 2005 * '' Cetopsis starnesi''

, 2005 * '' Cetopsis umbrosa''

, 2005

References

{{Taxonbar, from=Q5065684 Cetopsidae Fish of the Amazon basin Fish of Bolivia Catfish of Brazil Freshwater fish of Colombia Freshwater fish of Ecuador Freshwater fish of Peru Freshwater fish of Venezuela Catfish genera Taxa named by Louis Agassiz Freshwater fish genera