Cetopsis

{{Short description|Genus of fishes}} {{Automatic taxobox | image = The whale candiru Cetopsis coecutiens.jpg | image_caption = ''Cetopsis coecutiens'' | taxon = Cetopsis | authority = Agassiz, 1829 | type_species = ''Silurus coecutiens'' | type_species_authority = Lichtenstein, 1819 | subdivision_ranks = Species | subdivision = See text. | synonyms = {{Genus list | Hemicetopsis | Bleeker, 1862 | Pseudocetopsis | Bleeker, 1862 | Bathycetopsis | Lundberg & Rapp Py-Daniel, 1994 }} | synonyms_ref = <ref name = "Cof family">{{Cof family|family=Cetopsidae|access-date=13 November 2025}}</ref> }}

'''''Cetopsis''''' is a genus of freshwater ray-finned fishes belonging to the family Cetopsidae, the whale catfishes. The fishes in this genus are found in South America.

==Taxonomy== ''Cetopsis'' is one of four genera in the subfamily Cetopsinae within the family Cetopsidae.<ref name="Vari"/> ''Cetopsis'' is greatly expanded from when it only included ''C. coecutiens''. A number of genera were synonymized with ''Cetopsis'' to retain monophyly of cetopsine genera without erecting many new ones.<ref name="Vari"/>

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.<ref name="Vari"/>

==Distribution== ''Cetopsis'' species are found in major freshwater rivers draining to the east and west of South America, including the Amazon, Atrato, Madeira, Magdalena, Orinoco, Tocantins, and other rivers in Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela.<ref name="Vari"/>

==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, the absence of spines on the dorsal and pectoral fins, and the possession of a single row of teeth on the vomer.<ref name="Vari"/>

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. 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'', or ''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, though it lacks the fin ray elongations and convex anal fin margin of mature males.<ref name="Vari"/>

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'', and ''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 a narrow pale distal margin, while ''C. orinoco'' has dark pigmentation on the caudal fin, particularly on the distal portions of the fin.<ref name="Vari"/>

The body of ''Cetopsis'' species ranges from slender to stout. Unlike all other species, ''C. candiru'' has incisiform (vs. conical) teeth on the vomer and dentary, 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 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.<ref name="Vari"/>

''C. oliveirai'' has been found to be a paedomorphic species of the genus ''Cetopsis'', with many traits similar to juveniles of ''C. coecutiens''.<ref name="de Pinna">{{cite journal|last=de Pinna|first=MCC|author2=Ferraris, CJ, Jr. |author3=Vari, RP |year=2007|title=A phylogenetic study of the neotropical catfish family Cetopsidae (Osteichthyes, Ostariophysi, Siluriformes), with a new classification|journal=Zoological Journal of the Linnean Society|volume=150|issue=4|pages=755–813|doi=10.1111/j.1096-3642.2007.00306.x|doi-access=free}}</ref>

==Ecology== ''C. arcana'' was collected in a karstic region of the upper Tocantins River basin in both epigean (above-ground) and subterranean waters.<ref name="Vari"/> ''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.<ref name="Vari"/> ''C. motatanensis'' is found in swiftly flowing water among rubble to coarse gravel.<ref name="Vari"/> ''C. oliveirai'' originates in white water systems at depths of 2–40 m, and feeds on terrestrial arthropods.<ref name="Vari"/> ''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.<ref name="Vari"/> ''C. plumbea'' is reported to feed on a variety of terrestrial and aquatic insects. 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.<ref name="Vari"/> ''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.<ref name="Vari">{{cite journal|title=The Neotropical whale catfishes (Siluriformes: Cetopsidae: Cetopsinae), a revisionary study|first=Richard P.|last=Vari|author2=Ferraris, Carl J.|author3=de Pinna, Mário C. C.|journal=Neotropical Ichthyology|volume=3|issue=2|pages=127–238|year=2005|doi=10.1590/S1679-62252005000200001|doi-access=free}}</ref> ''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'' and BBC'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.<ref>River monsters{{full citation needed|date=August 2016}}</ref><ref>Amazon Abyss{{full citation needed|date=August 2016}}</ref>{{Better source|date=August 2018}}

==Species== [[File:Cetopsis othonops (16333761008).jpg|thumb|''Cetopsis othonops'']] [[File:Cetopsis plumbea.jpg|thumb|''Cetopsis plumbea'']] There are currently 23 recognized species in this genus:<ref>{{Cof genus | genus = Cetopsis| access-date = 15 October 2025}}</ref>

* ''Cetopsis amphiloxa'' (C. H. Eigenmann, 1914) * ''Cetopsis arcana'' Vari, Ferraris & de Pinna, 2005 * ''Cetopsis aspis'' Abrahão, Mol & de Pinna, 2019 * ''Cetopsis baudoensis'' (Dahl, 1960) * ''Cetopsis caiapo'' Vari, Ferraris & de Pinna, 2005 * ''Cetopsis candiru'' Spix & Agassiz, 1829 * ''Cetopsis coecutiens'' (M. H. C. Lichtenstein, 1819) * ''Cetopsis fimbriata'' [Vari, Ferraris & de Pinna, 2005 * ''Cetopsis gobioides'' Kner, 1858 * ''Cetopsis jurubidae'' (Fowler, 1944) * ''Cetopsis montana'' Vari, Ferraris & de Pinna, 2005 * ''Cetopsis motatanensis'' (L. P. Schultz, 1944) * ''Cetopsis oliveirai'' (Lundberg & Rapp Py-Daniel, 1994) * ''Cetopsis orinoco'' (L. P. Schultz, 1944) * ''Cetopsis othonops'' (C. H. Eigenmann, 1912) * ''Cetopsis parma'' J. C. de Oliveira, Vari & Ferraris, 2001 * ''Cetopsis pearsoni'' Vari, Ferraris & de Pinna, 2005 * ''Cetopsis plumbea'' Steindachner, 1882 * ''Cetopsis sandrae'' Vari, Ferraris & de Pinna, 2005 * ''Cetopsis sarcodes'' Vari, Ferraris & de Pinna, 2005 * ''Cetopsis starnesi'' Vari, Ferraris & de Pinna, 2005 * ''Cetopsis umbrosa'' Vari, Ferraris & de Pinna, 2005 * ''Cetopsis varii'' Abrahão & de Pinna, 2018

==References== {{Reflist}}

Category:Cetopsidae Category:Cetopsis Category:Fish of the Amazon basin Category:Fish of Bolivia Category:Catfish of Brazil Category:Freshwater fish of Colombia Category:Freshwater fish of Ecuador Category:Freshwater fish of Peru Category:Freshwater fish of Venezuela Category:Catfish genera Category:Taxa named by Louis Agassiz Category:Freshwater fish genera