Sorubim
Encyclopedia
Sorubim is a small genus
of Pimelodid
catfish
originating from tropical
South America. A number of characteristics allows the differentiation of each species in the genus. Sorubim are important food fish in South America and are highly significant to fisheries of some areas; however, harvests of these fish are not identified as much as other, more popular food fishes such as Colossoma
, Arapaima
, and Brachyplatystoma
. Some species of this family are popular aquarium
fish.
and Agassiz
in 1829, but because Cuvier's description predates that of Agassiz's by two months, Cuvier's is valid. Later, Sorubim lima, originally described as Siluris lima in 1801, was designated as the type species by Bleeker
in 1862.
In 2007 this genus was reviewed, validating five species. S. lima and S. trigonocephalus are redescribed in this paper. This genus is monophyletic
.
in the Amazon
, Orinoco, Parana
, and Parnaiba
basins. It is syntopic with S. elongatus in the Orinoco basin and with S. elongatus and S. maniradii in the upper Amazon drainage of Brazil
, Ecuador
, Peru
, and Bolivia
. S. maniradii was discovered in the Napo
and Yasumi River drainages of Ecuador, but also occurs in other tributaries of the Amazon. S. elongatus is found in the Amazon, Orinoco, and Essequibo River
basins. S. cuspicaudus is found in northern Colombia
and inhabits Lake Maracaibo
, Sinu River
, Cauca River
, and Magdalena River
basins. S. trigonocephalus is the rarest of the genus; only three specimens have ever been collected, from the Tapajos River and the Madeira River
.
Sorubim are found in fast-moving water and slow-moving water, including lakes, rivers, and bays. Typically the substrate is either sand
, clay
, and mud
, associating themselves with reeds
, grass
es, and root
s. They are not found as often over substrates of strictly sand or mud. They are also not found as commonly in clearer blackwater
habitats. S. elongatus occurs in both whitewater and blackwater, found in floodplain lakes and small creeks to large rivers. S. lima is commonly found in schools.
, these fish have very long barbels, especially maxillary barbels, which range in length from reaching the pectoral fin to extending past the pelvic fins. Like some other Pimelodid genera, these fish may have long filaments on their dorsal, pectoral, and caudal fins; in juveniles, these filaments may be even longer than the body. Sorubim is characterized by a shovel
-like, projecting upper jaw with an exposed, villiform (brush-like) premaxillary tooth patch. The head is depressed and usually three times longer than it is wide. The eyes are set laterally and usually visible from below. They have a characteristic black, lateral stripe, variable in width, that extends from the snout to the end of the caudal fin; though this may seem minor, no other Pimelodid has a lateral stripe that reaches down the entire length of the head and body.
Along with the lateral stripe, Sorubim species have a darkened dorsal surface, which are sometimes separated by a thinner, lighter-colored band. The dorsal surface may change its shade quickly with its surroundings. Sorubim lima may also display dark blotches or spots on its dorsal surface. The ventral part of the body is white or cream colored. Light areas may appear golden or slate gray, often appearing iridescent
. Young fish are more heavily pigmented than adults. Posterior-most rays on dorsal, anal, and pelvic fins are elongated, darker, and heavily speckled with chromatophores; however, this speckling is reduced in the adults. This could provide camouflage
when the fish is young and hiding among plant materials, and is lost when the adults live in more open water habitats.
S. lima appears similar to S. trigonocephalus; however, the latter has a long snout, pointed (triangular) head, and an exposed patch of premaxillary teeth that is as wide as it is long. S. cuspicaudus is markedly different caudal tail (straight, pointed, and long) is in contrast to the other Sorubim with more rounded caudal fin lobes. S. maniradii is differentiated from the other species by a high number of gill rakers, ranging from 31-37 rakers, compared to the 13-23 of the other Sorubim species, as well as a more diffuse lateral stripe. S. elongatus has an elongated head and body, and appears rather slender in comparison to the other members of this genus.
S. cuspicaudus is the largest species in the genus, reaching up to 80 centimetres (30 in). S. trigonocephalus and S. lima reach a length of about 50 cm (20 in). By contrast, S. elongatus and S. maniradii only reaches about half that length, 30 cm (12 in) in the former and 25 cm (10 in) in the latter.
. Natural history and reproduction of this fish are not well known. When inactive, these fish often swim in a vertical posture, probably to help blend into stems of reeds and other aquatic plants; when active, they swim in a normal, horizontal manner. They may use this camouflage either to hide from predators or as part of ambush predation
. These fish feed on fish and crustaceans, and as adults are largely piscivorous
. Sorubim have been observed in captivity to excavate a small pit as a nest and even guarding freshly hatched young (unfortunately, none of these young survived).
These fish are nocturnal and occur in groups or schools.
This fish is lazy and slow-moving; being nocturnal, it will usually hide during the day. This fish will accept most food, but it will also consume smaller inhabitants. It is hardy and the pH
is not of great importance, but slightly acidic is best. This fish requires a large aquarium. This fish prefers a current as well as clean water. It has not yet been bred in captivity.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of Pimelodid
Pimelodidae
Pimelodidae, commonly known as the long-whiskered catfishes, is a family of catfishes .-Taxonomy:Pimelodidae has undergone much revision. Currently, the family contains about 30 genera and about 90 recognized and known but unnamed species...
catfish
Catfish
Catfishes 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 heaviest and longest, the Mekong giant catfish from Southeast Asia and the second longest, the wels catfish of Eurasia, to detritivores...
originating from tropical
Tropics
The tropics is a region of the Earth surrounding the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately N and the Tropic of Capricorn in the southern hemisphere at S; these latitudes correspond to the axial tilt of the Earth...
South America. A number of characteristics allows the differentiation of each species in the genus. Sorubim are important food fish in South America and are highly significant to fisheries of some areas; however, harvests of these fish are not identified as much as other, more popular food fishes such as Colossoma
Pacú
Pacu or pacú is the common name of several South American fishes.PACU, Pacu or pacú may also refer to:*Piaractus mesopotamicus , a South American ray-finned fish that is endemic to the Paraguay-Paraná River basin*Tambaqui , known as black pacu, black-finned pacu, giant pacu*Philippine Association...
, Arapaima
Arapaima
The arapaima, pirarucu, or paiche is a South American tropical freshwater fish. It is a living fossil and one of the largest freshwater fishes in the world.-Anatomy and morphology:...
, and Brachyplatystoma
Brachyplatystoma
Brachyplatystoma is a genus of catfish from the family Pimelodidae. As the occasionally used common name goliath catfishes indicates, this genus includes some of the largest species of catfish, including the Piraíba, B. filamentosum, which reaches about in length...
. Some species of this family are popular aquarium
Aquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
fish.
Taxonomy
The genus name is derived from a Brazilian local name, Sorubí. The description of Sorubim has been attributed to both CuvierGeorges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...
and Agassiz
Louis Agassiz
Jean Louis Rodolphe Agassiz was a Swiss paleontologist, glaciologist, geologist and a prominent innovator in the study of the Earth's natural history. He grew up in Switzerland and became a professor of natural history at University of Neuchâtel...
in 1829, but because Cuvier's description predates that of Agassiz's by two months, Cuvier's is valid. Later, Sorubim lima, originally described as Siluris lima in 1801, was designated as the type species by Bleeker
Pieter Bleeker
Pieter Bleeker was a Dutch medical doctor and ichthyologist, famous for his work on the fishes of East Asia – Atlas Ichthyologique des Orientales Neerlandaises – which was published 1862–1877....
in 1862.
In 2007 this genus was reviewed, validating five species. S. lima and S. trigonocephalus are redescribed in this paper. This genus is monophyletic
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
.
Distribution and habitat
Sorubim is a widely distributed genus, collected from many major river basins and ten countries. S. lima is the most widely distributed species of the genus, found east of the AndesAndes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...
in the Amazon
Amazon River
The Amazon of South America is the second longest river in the world and by far the largest by waterflow with an average discharge greater than the next seven largest rivers combined...
, Orinoco, Parana
Paraná River
The Paraná River is a river in south Central South America, running through Brazil, Paraguay and Argentina for some . It is second in length only to the Amazon River among South American rivers. The name Paraná is an abbreviation of the phrase "para rehe onáva", which comes from the Tupi language...
, and Parnaiba
Parnaiba River
The Parnaíba River is a river in Brazil, which forms the border between the states of Maranhão and Piauí. The Parnaíba River rises in the Chapada das Mangabeiras range, and flows northeastward for 1,056 miles to empty into the Atlantic Ocean. The middle and upper regions of this river are...
basins. It is syntopic with S. elongatus in the Orinoco basin and with S. elongatus and S. maniradii in the upper Amazon drainage of Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
, Peru
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
, and Bolivia
Bolivia
Bolivia officially known as Plurinational State of Bolivia , is a landlocked country in central South America. It is the poorest country in South America...
. S. maniradii was discovered in the Napo
Napo River
The Napo is a tributary to the Amazon River that rises in Ecuador on the flanks of the volcanoes of Antisana, Sincholagua and Cotopaxi.The total length of 1075 km. Catchment area of 100,518 square kilometers...
and Yasumi River drainages of Ecuador, but also occurs in other tributaries of the Amazon. S. elongatus is found in the Amazon, Orinoco, and Essequibo River
Essequibo River
The Esequibo River is the largest river in Guyana, and the largest river between the Orinoco and Amazon. Rising in the Acarai Mountains near the Brazil-Guyana border, the Essequibo flows to the north for 1,010 km through forest and savanna into the Atlantic Ocean.-Geography:There are countless...
basins. S. cuspicaudus is found in northern Colombia
Colombia
Colombia, officially the Republic of Colombia , is a unitary constitutional republic comprising thirty-two departments. The country is located in northwestern South America, bordered to the east by Venezuela and Brazil; to the south by Ecuador and Peru; to the north by the Caribbean Sea; to the...
and inhabits Lake Maracaibo
Lake Maracaibo
Lake Maracaibo is a large brackish bay in Venezuela at . It is connected to the Gulf of Venezuela by Tablazo Strait at the northern end, and fed by numerous rivers, the largest being the Catatumbo. It is commonly considered a lake rather than a bay or lagoon, and at 13,210 km² it would be the...
, Sinu River
Sinú River
Sinú River , is a river in northwestern Colombia that flows mostly through the Córdoba Department and into the Caribbean. The river is the third most important river after the Magdalena River and the Cauca River in the Caribbean Region. It is born in the Antioquia Department, flowing south to north...
, Cauca River
Cauca River
The Cauca River is a river in Colombia that lies between the Occidental and Central cordilleras. Born in southwestern Colombia near the city of Popayán, it joins the Magdalena River near Pinillos in Bolívar Department, and the combined river eventually flows out into the Caribbean Sea. It has a...
, and Magdalena River
Magdalena River
The Magdalena River is the principal river of Colombia, flowing northward about through the western half of the country. It takes its name from the biblical figure Mary Magdalene. It is navigable through much of its lower reaches, in spite of the shifting sand bars at the mouth of its delta, as...
basins. S. trigonocephalus is the rarest of the genus; only three specimens have ever been collected, from the Tapajos River and the Madeira River
Madeira River
The Madeira River is a major waterway in South America, approximately 3,250 km miles long The Madeira is the biggest tributary of the Amazon...
.
Sorubim are found in fast-moving water and slow-moving water, including lakes, rivers, and bays. Typically the substrate is either sand
Sand
Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.The composition of sand is highly variable, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal...
, clay
Clay
Clay is a general term including many combinations of one or more clay minerals with traces of metal oxides and organic matter. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure.- Formation :Clay minerals...
, and mud
Mud
Mud is a mixture of water and some combination of soil, silt, and clay. Ancient mud deposits harden over geological time to form sedimentary rock such as shale or mudstone . When geological deposits of mud are formed in estuaries the resultant layers are termed bay muds...
, associating themselves with reeds
Phragmites
Phragmites, the Common reed, is a large perennial grass found in wetlands throughout temperate and tropical regions of the world. Phragmites australis is sometimes regarded as the sole species of the genus Phragmites, though some botanists divide Phragmites australis into three or four species...
, grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es, and root
Root
In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial or aerating . Furthermore, a stem normally occurring below ground is not exceptional either...
s. They are not found as often over substrates of strictly sand or mud. They are also not found as commonly in clearer blackwater
Blackwater river
A blackwater river is a river with a deep, slow-moving channel that flows through forested swamps and wetlands. As vegetation decays in the water, tannins are leached out, resulting in transparent, acidic water that is darkly stained, resembling tea or coffee. Most major blackwater rivers are in...
habitats. S. elongatus occurs in both whitewater and blackwater, found in floodplain lakes and small creeks to large rivers. S. lima is commonly found in schools.
Anatomy and appearance
Sorubim, like other catfish, possess a dorsal and pectoral fin spines. They have a triangular adipose fin. As PimelodidaePimelodidae
Pimelodidae, commonly known as the long-whiskered catfishes, is a family of catfishes .-Taxonomy:Pimelodidae has undergone much revision. Currently, the family contains about 30 genera and about 90 recognized and known but unnamed species...
, these fish have very long barbels, especially maxillary barbels, which range in length from reaching the pectoral fin to extending past the pelvic fins. Like some other Pimelodid genera, these fish may have long filaments on their dorsal, pectoral, and caudal fins; in juveniles, these filaments may be even longer than the body. Sorubim is characterized by a shovel
Shovel
A shovel is a tool for digging, lifting, and moving bulk materials, such as soil, coal, gravel, snow, sand, or ore. Shovels are extremely common tools that are used extensively in agriculture, construction, and gardening....
-like, projecting upper jaw with an exposed, villiform (brush-like) premaxillary tooth patch. The head is depressed and usually three times longer than it is wide. The eyes are set laterally and usually visible from below. They have a characteristic black, lateral stripe, variable in width, that extends from the snout to the end of the caudal fin; though this may seem minor, no other Pimelodid has a lateral stripe that reaches down the entire length of the head and body.
Along with the lateral stripe, Sorubim species have a darkened dorsal surface, which are sometimes separated by a thinner, lighter-colored band. The dorsal surface may change its shade quickly with its surroundings. Sorubim lima may also display dark blotches or spots on its dorsal surface. The ventral part of the body is white or cream colored. Light areas may appear golden or slate gray, often appearing iridescent
Iridescence
Iridescence is generally known as the property of certain surfaces which appear to change color as the angle of view or the angle of illumination changes...
. Young fish are more heavily pigmented than adults. Posterior-most rays on dorsal, anal, and pelvic fins are elongated, darker, and heavily speckled with chromatophores; however, this speckling is reduced in the adults. This could provide camouflage
Camouflage
Camouflage is a method of concealment that allows an otherwise visible animal, military vehicle, or other object to remain unnoticed, by blending with its environment. Examples include a leopard's spotted coat, the battledress of a modern soldier and a leaf-mimic butterfly...
when the fish is young and hiding among plant materials, and is lost when the adults live in more open water habitats.
S. lima appears similar to S. trigonocephalus; however, the latter has a long snout, pointed (triangular) head, and an exposed patch of premaxillary teeth that is as wide as it is long. S. cuspicaudus is markedly different caudal tail (straight, pointed, and long) is in contrast to the other Sorubim with more rounded caudal fin lobes. S. maniradii is differentiated from the other species by a high number of gill rakers, ranging from 31-37 rakers, compared to the 13-23 of the other Sorubim species, as well as a more diffuse lateral stripe. S. elongatus has an elongated head and body, and appears rather slender in comparison to the other members of this genus.
S. cuspicaudus is the largest species in the genus, reaching up to 80 centimetres (30 in). S. trigonocephalus and S. lima reach a length of about 50 cm (20 in). By contrast, S. elongatus and S. maniradii only reaches about half that length, 30 cm (12 in) in the former and 25 cm (10 in) in the latter.
Ecology
Because of the natural whitewater habitats of these fish which makes natural observation of this fish difficult, most observations of the behavior of this fish is largely known from study of fish in aquariaAquarium
An aquarium is a vivarium consisting of at least one transparent side in which water-dwelling plants or animals are kept. Fishkeepers use aquaria to keep fish, invertebrates, amphibians, marine mammals, turtles, and aquatic plants...
. Natural history and reproduction of this fish are not well known. When inactive, these fish often swim in a vertical posture, probably to help blend into stems of reeds and other aquatic plants; when active, they swim in a normal, horizontal manner. They may use this camouflage either to hide from predators or as part of ambush predation
Ambush predator
Ambush predators or sit-and-wait predators are carnivorous animals that capture prey by stealth or cunning, not by speed or necessarily by strength. These organisms usually hide motionless and wait for prey to come within striking distance. They are often camouflaged, and may be solitary...
. These fish feed on fish and crustaceans, and as adults are largely piscivorous
Piscivore
A piscivore is a carnivorous animal which eats primarily fish. Piscivory was the diet of early tetrapods , insectivory came next, then in time reptiles added herbivory....
. Sorubim have been observed in captivity to excavate a small pit as a nest and even guarding freshly hatched young (unfortunately, none of these young survived).
These fish are nocturnal and occur in groups or schools.
In the aquarium
S. lima has been in the aquarium trade for many years. S. lima is the most common species found in the aquarium trade. S. elongatus also appears rather often, and is sold as S. lima.This fish is lazy and slow-moving; being nocturnal, it will usually hide during the day. This fish will accept most food, but it will also consume smaller inhabitants. It is hardy and the pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...
is not of great importance, but slightly acidic is best. This fish requires a large aquarium. This fish prefers a current as well as clean water. It has not yet been bred in captivity.