''Cetopsis'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

catfish Catfish (or catfishes; order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Named for their prominent barbels, which resemble a cat's whiskers, catfish range in size and behavior from the three largest species alive, ...

es (

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of d ...

Siluriformes) of the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

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 cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic grou ...

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 relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

, including the

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

Atrato Atrato is a municipality and town in the Chocó Department near the Pacific Ocean, Colombia. Climate Atrato has an extremely wet tropical rainforest climate A tropical rainforest climate, humid tropical climate or equatorial climate is a trop ...

Madeira ) , anthem = ( en, "Anthem of the Autonomous Region of Madeira") , song_type = Regional anthem , image_map=EU-Portugal_with_Madeira_circled.svg , map_alt=Location of Madeira , map_caption=Location of Madeira , subdivision_type=Sovereign st ...

, Magdalena,

Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers , with 76.3 percent of it in Venezuela and the remainder in Colombia. It is the fourth largest river in the wor ...

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 20 ...

, and other rivers in

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

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 ...

Colombia Colombia (, ; ), officially the Republic of Colombia, is a country in South America with insular regions in North America—near Nicaragua's Caribbean coast—as well as in the Pacific Ocean. The Colombian mainland is bordered by the Car ...

Ecuador Ecuador ( ; ; Quechua: ''Ikwayur''; Shuar: ''Ecuador'' or ''Ekuatur''), officially the Republic of Ecuador ( es, República del Ecuador, which literally translates as "Republic of the Equator"; Quechua: ''Ikwadur Ripuwlika''; Shuar: ''Eku ...

Peru , image_flag = Flag of Peru.svg , image_coat = Escudo nacional del Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (emblem), National seal , national_motto = "Fi ...

, and

Venezuela Venezuela (; ), officially the Bolivarian Republic of Venezuela ( es, link=no, República Bolivariana de Venezuela), is a country on the northern coast of South America, consisting of a continental landmass and many islands and islets in th ...

Description

''Cetopsis'' is distinguished from the other genera in the

Cetopsinae 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 ...

from the combination of the absence of a spinelet associated with the

dorsal fin A dorsal fin is a fin located on the back of most marine and freshwater vertebrates within various taxa of the animal kingdom. Many species of animals possessing dorsal fins are not particularly closely related to each other, though through conv ...

, the absence of spines on the dorsal and

pectoral fin Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as ...

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

vomer The vomer (; lat, vomer, lit=ploughshare) 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 maxill ...

. 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 distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They are covered with skin and joined together either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as se ...

. 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 female external genitalia not present in humans, which appears as a small, fleshy flab of tissue. The pa ...

, 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 anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

, 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, whiskerlike sensory organ near the mouth. Fish that have barbels include the catfish, the carp, the goatfish, the hagfish, the sturgeon, the zebrafish, the black dragonfish and some ...

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 is found in modern humans compared ...

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 rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...

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 (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

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 pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

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 and American wildlife documentary television programme produced for Animal Planet by Icon Films of Bristol, United Kingdom. It is hosted by extreme angler and biologist Jeremy Wade, who travels around the glo ...

and

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'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 ( el, Βάρη) is a southern suburb of Athens and former municipality in East Attica, Greece along the Athens coast. Since the 2011 local government reform it is part of the municipality Vari-Voula-Vouliagmeni, of which it is a municipal un ...

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

, 2005 * '' Cetopsis candiru''

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

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 rec ...

, 1829 * '' Cetopsis coecutiens'' ( 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 Lundberg is a surname of Danish language, Swedish origin. Lundberg means "wooded hill" or "mountain grove". Notable people with the surname include: A *Agneta Lundberg (born 1947), Swedish Social Democratic politician *Alfred Lundberg (1852–1935 ...

& Rapp Py-Daniel, 1994) * '' Cetopsis orinoco'' ( L. P. Schultz, 1944) * '' Cetopsis othonops'' ( 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 describ ...

, 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 Fish of Brazil Fish of Colombia Fish of Ecuador Fish of Peru Fish of Venezuela Catfish genera Taxa named by Louis Agassiz Freshwater fish genera