''Cetopsis candiru'', also known as candiru, candiru açú, candiru cobra or canero, is a carnivorous species of whale catfish found in the

Amazon basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries ...

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 ...

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 ...

and

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 ...

. Similar to ''

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 ...

'', ''Cetopsis candiru'' is a large species of the genus ''Cetopsis'' and a widespread scavenger, known for its voracious feeding and the habit of burrowing into the carcasses of dead animals and humans. Despite its name, it is not closely related to the bloodsucking Candiru (''Vandellia cirrhosa'').

Names

They are known by multiple names across their range. In Bolivia they are called "Canero" or just "Candiru". The term "Canero" is also used in Peru. Candiru açú is also used on occasion, however according to some researchers this name is primarily used for other species of the genus ''Cetopsis'' including ''C. coecutiens'' and ''C. gobioides''. Alternatively the name "candiru cobra" is also used. The name Candiru is shared by ''

Vandellia cirrhosa Candiru (''Vandellia cirrhosa''), also known as cañero, toothpick fish, or vampire fish, is a species of parasitic freshwater catfish in the family Trichomycteridae native to the Amazon basin where it is found in the countries of Bolivia, Braz ...

'', a parasitic catfish from the family

Trichomycteridae Trichomycteridae is a family of catfishes commonly known as pencil catfishes or parasitic catfishes. This family includes the candiru fish (''Vandellia cirrhosa''), feared by some people for its alleged habit of entering into the urethra of ...

which is otherwise unrelated to members of the Cetopsidae.

Description

The body of ''Cetopsis candiru'' is elongated and smooth with a broadly rounded, triangular head. The eyes are located on the dorsolateral surface of the head and situated far towards the front of the skull within the first fifth of the head length. They are small, only around as large as the circular anterior nares, which are surrounded by a rim of skin. In addition to the anterior nares, ''Cetopsis candiru'' also possesses a second pair of nares further back on the skull that open towards the top of the body, which are also surrounded by tubular skin. The mouth is located low on the head and around half as wide as the head is long. The margins of the lower jaw are shortened and reach approximately as far back as the eyes. The teeth of the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...

are incisiform and form a single, gently curved row. In addition to them ''C. candiru'' also possesses 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 ...

which share their incisiform morphology with those of the premaxilla and are likewise arranged in a single curved row. Finally the dentary mimics the same tooth arrangement, if notably larger compared to the premaxillary and vomerine dentition. Through this ''C. candiru'' differs from its relatives, known for having conical teeth on the vomer and dentary. Like many other species of catfish, ''Cetopsis candiru'' has long, whisker-like growths known as

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 ...

. The maxillary barbels are about a third of the length of the skull and originate below the front-most edge of the eyes. Two pairs of mental barbels are present on the lower jaw and equal in length and size to those of the maxilla. 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 ...

is relatively small and located towards the front of the body, lacking spines. The base of the

caudal 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 only ...

(caudal peduncle) is approximately as deep as it is long. The caudal fin itself is symmetrical and slightly forked, with the rounded lobes approximately 1.5 to 1.6 times longer than the shallowest part of the fin. 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 ...

is located in the back half of the body and its base takes up approximately a third of the animal's length. Its shape is gently convex and its rear end does not attach to the body. In ''Cetopsis candiru'' the

pelvic fins Pelvic fins or ventral fins are paired fins located on the ventral (belly) surface of fish, and are the lower of the only two sets of paired fins (the other being the laterally positioned pectoral fins). The pelvic fins are homologous to the hi ...

are short and paddle-like with rounded symmetrical edges. Like with the anal fin, there is no membrane attaching the last fin ray directly to the body. Finally the

pectoral fins 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 only b ...

are around half as long as the head with rounded edges. Mature males however differ from females and juveniles in the morphology of some of their fins. The first fin rays of both the dorsal and pectoral fins are distinctly elongated beyond what can be seen in younger or female individuals and the anal fin is noticeably more convex. When this

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

sets in is not fully known. The smallest specimen showing all of these traits measured in standard length (tip of the skull to the end of the hypural plate). Another, smaller individual measuring shows the onsets of these elements' growth. Alongside ''C. coecutiens'', ''C. candiru'' is one of the largest species within the genus ''Cetopsis''. They range in size from to .

Ecology

''Cetopsis candiru'' is a carnivorous fish and commonly described as a voracious feeder, making use of powerful jaw musculature and a nearly continuous cutting surface of the incisiform dentition. Their distribution overlaps with that of the related ''

'' and both species are known to simultaneously feed on the same bodies. They do however differ in the specifics of their behavior. ''Cetopsis candiru'' typically bite into carcasses and twist to create an entry into the body before proceeding to feed from the inside, where they may congregate in vast numbers during feeding frenzies. Due to these habits carcasses that were fed on by ''C. candiru'' oftentimes appear almost entirely skeletonized, but retain cartilage, eyeballs and tight skin. ''Cetopsis coecutiens'' on the other hand does not remain inside the body and instead will return to it multiple times, each time ripping away chunks of flesh. Both species leave similar circular bitemarks on bodies they scavenged on. They are opportunistic animals, feeding on the carcasses of animals that have drowned or otherwise died and fallen into the water. The role of these fish as important aquatic scavengers is highlighted by their prominent appearance in

forensics Forensic science combines principles of law and science to investigate criminal activity. Through crime scene investigations and laboratory analysis, forensic scientists are able to link suspects to evidence. An example is determining the time and ...

around the Amazon, being well known to even feed on dead human bodies found in the various rivers of northern South America. At least one confirmed report tells of a single ''Cetopsis'' attacking a living child, although the exact culprit could not be determined between the two carnivorous species ''C. candiru'' and ''C. coecutiens''. Other reports mention ''Cetopsis candiru'' feeding on live fish caught in

gillnets Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...

or hooked by fishermen.

Distribution

''Cetopsis candiru'' is known across large parts of the

Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries ...

. Specimens have been discovered in

close to the Amazon River itself, the Rio Tocantins, the Rio Negro, the

Rio Purus The Purus River (Portuguese: ''Rio Purus''; Spanish: ''Río Purús'') is a tributary of the Amazon River in South America. Its drainage basin is , and the mean annual discharge is . The river shares its name with the Alto Purús National Park a ...

and the Rio Madeira among others. In

they occur in various

tributaries A tributary, or an ''affluent'', is a stream or river that flows into a larger stream ('' main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which the ...

to the Rio Madeira such as the Rio Beni and in

they were recovered from the Rio Ucayali and other tributaries to the Amazon. Some scientists also report the presence of ''Cetopsis candiru'' from eastern

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 ...

Taxonomy and classification

''Cetopsis candiru'' was first described in 1829 by Spix & Agassiz on the basis of four

syntype In biological nomenclature, a syntype is any one of two or more biological types that is listed in a description of a taxon where no holotype was designated. Precise definitions of this and related terms for types have been established as part o ...

specimens. The same year

Cuvier Jean Léopold Nicolas Frédéric, baron Cuvier (23 August 1769 – 13 May 1832), known as Georges Cuvier (; ), was a French natural history, naturalist and zoology, zoologist, sometimes referred to as the "founding father of paleontology". Cuv ...

established the name ''Silurus candira'', which however is a ''

nomen nudum In Taxonomy (biology), taxonomy, a ''nomen nudum'' ('naked name'; plural ''nomina nuda'') is a designation which looks exactly like a scientific name of an organism, and may have originally been intended to be one, but it has not been published ...

''. Several other names were subsequently coined, none of which however remained. In 1839 ''Cetopsis spixii'' was introduced in an attempt to replace the prior name and in 1862 ''C. candiru'' was chosen to serve as the type species of the newly erected genus ''Hemicetopsis''. Several synonyms are also the result of authors variously using either "candiru" or "candira" as the

species name In taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, altho ...

. Studies have found that ''Cetopsi candiru'' is closely related to the large and carnivorous ''Cetopsis coecutiens'' as well as the diminutive ''Cetopsis oliveirai''. This presents a diverse clade formed by the three, as it includes both the two largest and one of the smallest species of the genus. Additionally, all three species are highly distinct, having each been placed in different genera at varying points in the past (''Hemicetopsis'', ''Cetopsis'' and ''Bathycetopsis''). The idea that they form a

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 within ''Cetopsis'' is well supported and comparison between adults of ''C. oliveirai'' show that the species appears much like juveniles of ''C. coecutiens''. A sister relationship between ''C. coecutiens'' and ''C. candiru'' however is not as well supported.

References

{{Taxonbar, from=Q5590003 Cetopsidae Fish of the Amazon basin Fish of Bolivia Catfish of Brazil Freshwater fish of Ecuador Freshwater fish of Peru Taxa named by Louis Agassiz Freshwater fish