''Cetopsidium'' 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

''Cetopsidium'' was described in 2005, its name coming from the ''

Cetopsis ''Cetopsis'' is a genus of catfishes ( order Siluriformes) of the family Cetopsidae. Taxonomy ''Cetopsis'' is one of four genera in the subfamily Cetopsinae within the family Cetopsidae. ''Cetopsis'' is greatly expanded from when it only include ...

'', the first described cetopsid genus, and ''idium'' which means diminutive, in reference to the relatively small size of ''Cetopsidium'' species. Three existing species were transferred to this genus and three new species were described. In 2009 a new species, ''Cetopsidium soniae'', was described bringing the number of species in the genus to seven.

Species

There are currently seven recognized species in this genus: * '' Cetopsidium ferreirai''

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 ...

Ferraris Ferrari Società per Azioni, S.p.A. (; ) is an Italian luxury sports car manufacturer based in Maranello, Italy. Founded by Enzo Ferrari (1898–1988) in 1939 from the Alfa Romeo racing division as ''Auto Avio Costruzioni'', the company buil ...

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 * '' Cetopsidium minutum'' ( C. H. Eigenmann, 1912) * '' Cetopsidium morenoi'' ( Fernández-Yépez, 1972) * '' Cetopsidium orientale'' (

Keith Keith may refer to: People and fictional characters * Keith (given name), includes a list of people and fictional characters * Keith (surname) * Keith (singer), American singer James Keefer (born 1949) * Baron Keith, a line of Scottish barons ...

, 2003) * '' Cetopsidium pemon''

, 2005 * '' Cetopsidium roae''

, 2005 * '' Cetopsidium soniae''

, 2009

Distribution

Fishes of this genus are found in the rivers of northern

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 ...

Description

The combination of the presence of a

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 ...

with an ossified spinelet and the presence of pectoral-fin and dorsal-fin spines distinguishes the species of ''Cetopsidium'' from all other genera in the Cetopsinae. A

lateral line The lateral line, also called the lateral line organ (LLO), is a system of sensory organs found in fish, used to detect movement, vibration, and pressure gradients in the surrounding water. The sensory ability is achieved via modified epithelial ...

extending to over the posterior portion of the base of 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 ...

but falling short of the

caudal peduncle 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 ...

is also unique in this genus; the lateral line is usually longer than this, though it is shorter in two species of ''

Denticetopsis ''Denticetopsis'' is a genus of catfishes ( order Siluriformes) of the family Cetopsidae. Taxonomy Originally ''Denticetopsis'' as described by Ferraris in 1996 was restricted to two species, ''D. royeroi'' and ''D. sauli''. These two species ha ...

''. ''Cetopsidium'' species have mental barbels extending posteriorly beyond the rear margin of the

opercle The operculum is a series of bones found in bony fish and chimaeras that serves as a facial support structure and a protective covering for the gills; it is also used for respiration and feeding. Anatomy The opercular series contains four bon ...

and a deeply forked, symmetrical caudal-fin margin with the tips of the lobes slightly blunt or rounded. The body is elongate to moderately robust; anteriorly the body is not compressed much, but becomes progressively compressed posteriorly. The lateral line is incomplete, unbranched, and midlateral. In most species the dorsal profile is straight, though it may be slightly convex from the head to the dorsal fin origin in some species. The ventral profile is slightly convex at the abdomen but is straight posteriorly. The

depth is approximately equal to its length in most species, though the depth is less than the length in ''C. roae'' and greater in ''C. orientale''. The eyes are placed on the sides of the head and are visible from above, but not from below. The mouth is subterminal and its width is anywhere between 40–60% of the head length. They have three pairs of barbels, one pair of maxillary barbels and two pairs of mental barbels; the medial mental barbels are slightly shorter than the lateral mental barbels, which are in turn slightly shorter than the slender maxillary barbels. The

is moderately long, beginning about halfway down the body, with the posterior-most anal fin rays with a slight, membranous attachment to the body. The

pelvic fin Pelvic fins or ventral fins are paired fins located on the ventral surface of fish. The paired pelvic fins are homologous to the hindlimbs of tetrapods. Structure and function Structure In actinopterygians, the pelvic fin consists of two en ...

s are usually small. The first pectoral fin ray is spinous and is slightly longer than one-half the length of the first branched ray; however, the spine may have a prolonged distal filament in mature males.

Sexual dimorphism Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...

is observed in ''C. ferreirai'', ''C. morenoi'', ''C. orientale'', and ''C. pemon'', but not in ''C. minutum'' or ''C. roae''. Presumed mature males have the first ray of the dorsal and pectoral fins extended into filaments except in ''C. ferreirai''. Also, the anal fin has a broadly

convex Convex or convexity may refer to: Science and technology * Convex lens, in optics Mathematics * Convex set, containing the whole line segment that joins points ** Convex polygon, a polygon which encloses a convex set of points ** Convex polytope ...

margin rather than a straight margin. ''Cetopsidium'' species are smaller than ''Cetopsis'' species, growing to only SL.

References

{{Taxonbar, from=Q5065683 Cetopsidae Fish of South America Fish of Brazil Fish of Colombia Fish of French Guiana Fish of Guyana Fish of Suriname Fish of Venezuela Catfish genera Freshwater fish genera