''Cheirocerus'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

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 and Dutch 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, Schul ...

, 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 m ...

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 n ...

, 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 descri ...

, 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 approximately 1 million km2, with 65% of it in Venezuela and 35% in Colombia. It is the List of rivers by discharge, f ...

. ''C. abuelo'' occurs in the

Lake Maracaibo Lake Maracaibo () is located in northwestern Venezuela, between the states of Zulia, Trujillo, and Mérida. While Maracaibo is commonly referred to as a lake, its current hydrological characteristics may better classify it as estuary and/or ...

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 is . The river shares its name with the Alto Purús National Park a ...

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 Mountain Range (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long and wide (widest between 18°S ...

foothills where rivers may be cooler and shallower.

Description

Species of ''Cheirocerus'' have a fully

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. 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 mammals h ...

, a crimped

gas bladder The swim bladder, gas bladder, fish maw, or air bladder is an internal gas-filled organ in bony fish that functions to modulate buoyancy, and thus allowing the fish to stay at desired water depth without having to maintain lift via swimming, ...

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 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 ...

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

adipose 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 b ...

. These species all have three pairs of

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 ...

. ''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 , ). The corresponding adjective is ''nuchal'', as in the term ''nuchal rigidity'' ...

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 the Ancient Greek word (), meaning "the depths". ...

invertebrates, with

chironomid Chironomidae , commonly known as non-biting midges or chironomids , are a family of Nematoceran flies with a global distribution. They are closely related to the families Ceratopogonidae, Simuliidae, and Thaumaleidae. Although many chironomid s ...

larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...

e being a dominant component, but also including

ostracod Ostracods, or ostracodes, are a Class (biology), class of the crustacean, Crustacea (class Ostracoda), sometimes known as seed shrimp. Some 33,000 species (only 13,000 of which are extant taxon, extant) have been identified,Brandão, S.N.; Antoni ...

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 orde ...

nymph A nymph (; ; sometimes spelled nymphe) is a minor female nature deity in ancient Greek folklore. Distinct from other Greek goddesses, nymphs are generally regarded as personifications of nature; they are typically tied to a specific place, land ...

References

Pimelodidae Fish of South America Catfish genera Taxa named by Carl H. Eigenmann Freshwater fish genera {{Pimelodidae-stub