''Cheirocerus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

long-whiskered catfish The Pimelodidae, commonly known as the long-whiskered catfishes, are a family of catfishes (order Siluriformes). Taxonomy The family Pimelodidae has undergone much revision. Currently, it contains about 30 genera and about 90 recognized and know ...

es native to

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 souther ...

Species

There are currently three recognized species in this genus: * ''

Cheirocerus abuelo ''Cheirocerus abuelo'', is a species of demersal catfish of the family Pimelodidae The Pimelodidae, commonly known as the long-whiskered catfishes, are a family of catfishes (order Siluriformes). Taxonomy The family Pimelodidae has undergone ...

'' (

Schultz Schultz is a German surname derived from ''Schultheiß'', meaning village headman or constable/sheriff in the medieval sense (akin to today's office of mayor). It has many variations, such as Schuldt, Schulte, Schulten, Schultes, Schultheis, Sc ...

, 1944) * ''

Cheirocerus eques ''Cheirocerus eques'', is a species of demersal catfish of the family Pimelodidae The Pimelodidae, commonly known as the long-whiskered catfishes, are a family of catfishes (order Siluriformes). Taxonomy The family Pimelodidae has undergone ...

Eigenmann Eigenmann is a surname. Notable persons with that surname include: * Andi Eigenmann (born 1990), Filipino actress * Carl H. Eigenmann (1863–1927), German–American ichthyologist, husband of Rosa Eigenmann * Eduardo de Mesa Eigenmann, birth name ...

, 1917 * ''

Cheirocerus goeldii ''Cheirocerus goeldii'', is a species of demersal catfish of the family Pimelodidae that is native to Purus River basin and Das Velhas River basin of Brazil and Peru. It grows to a length of 15.2 cm. It is clearly distinguished from other ...

'' (

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 ...

, 1908)

Distribution and habitat

''Cheirocerus'' is distributed throughout much of the Amazon River basin, and appear to be absent from the

Orinoco River 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 wo ...

. ''C. abuelo'' occurs in the

Lake Maracaibo Lake Maracaibo ( Spanish: Lago de Maracaibo; Anu: Coquivacoa) is a lagoon in northwestern Venezuela, the largest lake in South America and one of the oldest on Earth, formed 36 million years ago in the Andes Mountains. The fault in the northern s ...

basin, ''C. eques'' in the Amazon River basin, and ''C. goeldii'' in the

Purus River 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 (hydrology), discharge is . The river shares its name with the Alto P ...

basin. ''C. goeldii'' is more typical of lowland large rivers where the water may be warmer and deeper, though it may also occur far upstream. ''C. eques'' appears to occur closer to

Andean The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S l ...

foothills where rivers may be cooler and shallower.

Description

Species of ''Cheirocerus'' have a fully

ventral Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

mouth with relatively fleshy lips, a broad

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 mammal has ...

, a crimped

gas bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ that contributes to the ability of many bony fish (but not cartilaginous fish) to control their buoyancy, and thus to stay at their current water depth wi ...

that appears to have fringe or finger-like projections, and the slender hollow tube extensions on each side of the gas bladder. These fish have an undeveloped

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 c ...

locking mechanism and no dorsal fin spine. They also have a relatively long

adipose 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 ...

. These species all have three pairs of

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 s ...

. ''C. eques'' and ''C. goeldii'' display some geographic variations in certain

morphometric Morphometrics (from Greek μορϕή ''morphe'', "shape, form", and -μετρία ''metria'', "measurement") or morphometry refers to the quantitative analysis of ''form'', a concept that encompasses size and shape. Morphometric analyses are co ...

characteristics. ''C. abuelo'' has a dusky-gray body colouration that varies from relatively plain to having numerous small brown spots, and usually has a broad, diffuse band crossing the

nape The nape is the back of the neck. In technical anatomical/medical terminology, the nape is also called the nucha (from the Medieval Latin rendering of the Arabic , "spinal marrow"). The corresponding adjective is ''nuchal'', as in the term ''nu ...

at the dorsal fin origin. Both ''C. goeldii'' and ''C. eques'' have a relatively uniform body colouration without spots; ''C. goeldii'' has a small, triangular spot at the dorsal fin origin, while ''C. eques'' has a distinct dark band at the dorsal fin origin. ''C. abuelo'' appears to attain the largest size of the three species, reaching at least . By contrast, the largest known ''C. eques'' is about and the largest ''C. goeldii'' is about .

Ecology

''Cheirocerus'' species are generally nocturnal. This is evidenced by the specialized gas bladder, hypothesized to enhance hearing, and the poorly developed pigmentation. Diet mostly consists of

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

invertebrates, with

chironomid The Chironomidae (informally known as chironomids, nonbiting midges, or lake flies) comprise a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae. Many species ...

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. Th ...

e being a dominant component, but also including

ostracod Ostracods, or ostracodes, are a class of the Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 70,000 species (only 13,000 of which are extant) have been identified, grouped into several orders. They are small crustaceans, typic ...

s and

mayfly Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern United States, as Canadian soldiers in the American Great Lakes region, and as up-winged flies in the United Kingdom) are aquatic insects belonging to the order ...

nymph A nymph ( grc, νύμφη, nýmphē, el, script=Latn, nímfi, label=Modern Greek; , ) in ancient Greek folklore is a minor female nature deity. Different from Greek goddesses, nymphs are generally regarded as personifications of nature, are ty ...

References

{{Taxonbar, from=Q5089698 Pimelodidae Fish of South America Catfish genera Taxa named by Carl H. Eigenmann Freshwater fish genera