Lasiancistrus
Encyclopedia
Lasiancistrus is a genus
of catfish
es (order
Siluriformes) of the family
Loricariidae
. It includes six species, L. caucanus, L. guacharote, L. heteracanthus, L. saetiger, L. schomburgkii, and L. tentaculatus.
in 1904, including A. heteracanthus, A. pictus, A. mystacinus, and A. guacharote. Later, it was raised to genus level, and several unrelated species were included. Many of these species have since been moved to other genera, such as Pseudolithoxus
. Most Lasiancistrus species had been described from few specimens; the genus was revised in 2005, synonymizing
many of the existing species into four species, L. caucanus, L. guacharote, L. heteracanthus, and L. schomburgkii. L. maracaiboensis and L. mystacinus are synonyms of L. guacharote. L. castelnaui, L. caquetae, L. guapore, L. multispinis, L. pictus, and L. scolymus are synonyms of L. schomburgkii. L. planiceps, L. mayoloi, and L. volcanensis are synonyms
of L. caucanus. In addition, two new species, L. saetiger and L. tentaculatus, were described.
basin, the upper and middle of the Orinoco
River basin, the Rupununi River basin (Essequibo River
drainage), the Lake Maracaibo
drainage, and drainages west of the Andes
in Colombia
and Panama
to the Bayano River
. L. caucanus has a trans
-Andean distribution in the Magdalena
, Atrato
, San Juan
, Tuyra, and Bayano drainages of Colombia and Panama. L. guacharote is known from the Lake Maracaibo
basin of Venezuela
and Colombia. L. heteracanthus is known from the upper Napo River
in Ecuador
and the lower Napo River and upper Amazon River in Peru
. L. saetiger is known from a single collection of fishes from the Guamá River
, a tributary of the Capim River, a drainage that enters the Atlantic just southeast of the mouth of the Amazon. L. schomburgkii has the greatest range of the species, and is found throughout much of the Amazon basin and the upper Orinoco and Essequibo River basins. L. tentaculatus is found in the Orinoco River basin of Colombia and Venezuela and in the Lake Valencia
drainage of Venezuela.
The species of Lasiancistrus are most commonly found in small creeks, typically in swift flow. However, some of the streams where Lasiancistrus can be found are in the lowlands, and hypoxia
has been observed in one such stream, suggesting that lowlands are not a barrier to the movement of these species. Lasiancistrus are most common in lower piedmont streams and are more likely to spread between rivers this way rather than through the lowlands.
s on their cheeks which are unique among the Loricariidae. These hair-like odontodes are part of their evertible cheek odontodes; they are very narrow, but appear to be made out of the same material as the other odontodes. Their presence does not appear to be sexually dimorphic
, although males may have longer ones. In nuptial males, there are fleshy tentacles on the pectoral-fin spines longer than their associated odontodes, which differentiates it from all genera except Ancistrus
. They are differentiated from Ancistrus by the presence of plates along the edge of the snout (Ancistrus lack these plates) and by maximally having translucent tentacles on the snout that have odontodes associated with them (in Ancistrus there are larger tentacles without associated odontodes coloured the same as the head).
The snout of nuptial males are almost square, rather than rounded as in females and juveniles. Adult males of most species (except L. tentaculatus) have whiskerlike odontodes at anterolateral corner of snout; in L. tentaculatus, males have tentacles instead of whiskerlike odontodes along anterior margin of snout. Also, nuptial males with tentacles longer than their associated odontodes on the pectoral-fin spine.
Lasiancistrus species are medium-sized loricariids, with the largest being about 19.0 centimetres (7.5 in) SL
. The body is strongly dorsoventrally compressed and moderately wide. The head and nape are gently sloped to the insertion of the dorsal fin. The ventral surface of the fish is flat. The head contours are smooth. The eyes are small to medium. The caudal fin is slightly emarginate to forked, with the lower lobe longer than the upper lobe. The dorsal flap of the iris is present. The lips are wide and fairly thin; the upper lip has small, round papilla
e and the lower lip has medium-sized papillae anteriorly and smaller ones posteriorly.
No morphometric
, meristic
, or skeletal differences could be found among the species of Lasiancistrus. The only differences
between the species are the degree of abdominal plating (itself a characteristic that is likely to be very homoplastic) and coloration. L. schomburgkii has a body and fins with small white spots less than half the diameter of the plates (although spots may be faded); its plates are entirely dark or with small spots. L. saetiger has a body and paired fins with large white spots almost the same size as the plates, with the dorsal fin without spots; its plates are outlined in black. In the rest of the species, the dorsal fin is with black spots, the body is with dark markings and light markings, if present, are usually present as blotches or thick lines (except in the Bayano River population in Panama of L. caucanus); the body is never completely dark. In L. caucanus and L. tentaculatus, the abdomen lacks plates; between these two species, L. caucanus has whiskerlike odontodes on the corners of the snout in nuptial males and an emarginate caudal fin, while L. tentaculatus has tentacles along the anterior margin of the snout in nuptial males and a forked caudal fin. In the remaining two species, the abdomen has plates in at least a small patch medial to the insertion of the pectoral-fin spines; in L. heteracanthus, the abdomen has plates underneath entire pectoral girdle and on the abdomen, while in L. guacharote, the abdomen has only a couple of plates medial to insertion of pectoral-fin spines.
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 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...
es (order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Siluriformes) of the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Loricariidae
Loricariidae
Loricariidae is the largest family of catfish , with almost 700 species and new species being described each year. Loricariids originate from fresh water habitats of Costa Rica, Panama, and tropical and subtropical South America. These fish are noted for the bony plates covering their bodies and...
. It includes six species, L. caucanus, L. guacharote, L. heteracanthus, L. saetiger, L. schomburgkii, and L. tentaculatus.
Taxonomy
Lasiancistrus was first described as a subgenus of AncistrusAncistrus
Ancistrus is a genus of freshwater fish in the family Loricariidae of order Siluriformes. Fish of this genus are commonly known as the bushynose or bristlenose plecos.-Taxonomy:The type species is Ancistrus cirrhosus...
in 1904, including A. heteracanthus, A. pictus, A. mystacinus, and A. guacharote. Later, it was raised to genus level, and several unrelated species were included. Many of these species have since been moved to other genera, such as Pseudolithoxus
Pseudolithoxus
Pseudolithoxus is a genus of catfishes of the family Loricariidae. It includes five species, P. anthrax, P. dumus, P. kelsorum, P. nicoi, and P. tigris, previously described as the Lasiancistrus anthrax group....
. Most Lasiancistrus species had been described from few specimens; the genus was revised in 2005, synonymizing
Synonym (taxonomy)
In scientific nomenclature, a synonym is a scientific name that is or was used for a taxon of organisms that also goes by a different scientific name. For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies...
many of the existing species into four species, L. caucanus, L. guacharote, L. heteracanthus, and L. schomburgkii. L. maracaiboensis and L. mystacinus are synonyms of L. guacharote. L. castelnaui, L. caquetae, L. guapore, L. multispinis, L. pictus, and L. scolymus are synonyms of L. schomburgkii. L. planiceps, L. mayoloi, and L. volcanensis are synonyms
of L. caucanus. In addition, two new species, L. saetiger and L. tentaculatus, were described.
Distribution and habitat
Unlike many other members of Ancistrini, the ranges of most of the Lasiancistrus species are quite broad. Lasiancistrus species are found throughout the Amazon RiverAmazon 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...
basin, the upper and middle of the Orinoco
Orinoco
The Orinoco is one of the longest rivers in South America at . Its drainage basin, sometimes called the Orinoquia, covers , with 76.3% of it in Venezuela and the remainder in Colombia...
River basin, the Rupununi River basin (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...
drainage), the 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...
drainage, and drainages west of the Andes
Andes
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 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 Panama
Panama
Panama , officially the Republic of Panama , is the southernmost country of Central America. Situated on the isthmus connecting North and South America, it is bordered by Costa Rica to the northwest, Colombia to the southeast, the Caribbean Sea to the north and the Pacific Ocean to the south. The...
to the Bayano River
Bayano River
A river of Panama in the Panama Province. It was dammed in the 70s, creating Lago Bayano. This dam provides much of the electrical power for Panama City....
. L. caucanus has a trans
Trans
Trans is a Latin noun or prefix, meaning "across", "beyond" or "on the opposite side".Trans may refer to:- Science and technology :* Cis-trans isomerism, in chemistry, a form of stereoisomerism...
-Andean distribution in the Magdalena
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...
, Atrato
Atrato River
The Río Atrato is a river of northwestern Colombia. It rises in the slopes of the Western Cordillera and flows almost due north to the Gulf of Urabá , where it forms a large, swampy delta....
, San Juan
San Juan River (Colombia)
San Juan River is an important river of Colombia. It quoted source is in the Cordillera Occidental and has a length of 380 km...
, Tuyra, and Bayano drainages of Colombia and Panama. L. guacharote is known from the 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...
basin of Venezuela
Venezuela
Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...
and Colombia. L. heteracanthus is known from the upper Napo River
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...
in 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...
and the lower Napo River and upper Amazon River in 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....
. L. saetiger is known from a single collection of fishes from the Guamá River
Guamá River
-References:*...
, a tributary of the Capim River, a drainage that enters the Atlantic just southeast of the mouth of the Amazon. L. schomburgkii has the greatest range of the species, and is found throughout much of the Amazon basin and the upper Orinoco and Essequibo River basins. L. tentaculatus is found in the Orinoco River basin of Colombia and Venezuela and in the Lake Valencia
Lake Valencia
Lake Valencia is the third largest lake in Venezuela, exceeded in size only by Lake Maracaibo and Lake Guri. It occupies one of the so-called Aragua valleys, enclosed between the parallel mountain ranges of the Cordillera de la Costa, the Maritime Andes. One part is within the limits of Carabobo...
drainage of Venezuela.
The species of Lasiancistrus are most commonly found in small creeks, typically in swift flow. However, some of the streams where Lasiancistrus can be found are in the lowlands, and hypoxia
Hypoxia (environmental)
Hypoxia, or oxygen depletion, is a phenomenon that occurs in aquatic environments as dissolved oxygen becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system...
has been observed in one such stream, suggesting that lowlands are not a barrier to the movement of these species. Lasiancistrus are most common in lower piedmont streams and are more likely to spread between rivers this way rather than through the lowlands.
Description
Adult Lasiancistrus have whiskerlike odontodeOdontode
Odontodes, or dermal teeth, are hard structures found on the external surfaces of animals or near internal openings. They comprise a soft pulp surrounded by dentine and covered by a mineralized substance such as enamel, a structure similar to that of teeth. They generally do not have the same...
s on their cheeks which are unique among the Loricariidae. These hair-like odontodes are part of their evertible cheek odontodes; they are very narrow, but appear to be made out of the same material as the other odontodes. Their presence does not appear to be sexually dimorphic
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
, although males may have longer ones. In nuptial males, there are fleshy tentacles on the pectoral-fin spines longer than their associated odontodes, which differentiates it from all genera except Ancistrus
Ancistrus
Ancistrus is a genus of freshwater fish in the family Loricariidae of order Siluriformes. Fish of this genus are commonly known as the bushynose or bristlenose plecos.-Taxonomy:The type species is Ancistrus cirrhosus...
. They are differentiated from Ancistrus by the presence of plates along the edge of the snout (Ancistrus lack these plates) and by maximally having translucent tentacles on the snout that have odontodes associated with them (in Ancistrus there are larger tentacles without associated odontodes coloured the same as the head).
The snout of nuptial males are almost square, rather than rounded as in females and juveniles. Adult males of most species (except L. tentaculatus) have whiskerlike odontodes at anterolateral corner of snout; in L. tentaculatus, males have tentacles instead of whiskerlike odontodes along anterior margin of snout. Also, nuptial males with tentacles longer than their associated odontodes on the pectoral-fin spine.
Lasiancistrus species are medium-sized loricariids, with the largest being about 19.0 centimetres (7.5 in) SL
Fish measurement
Fish measurement refers to the measuring of the length of individual fish and of various parts of their anatomy. These data are used in many areas of ichthyology, including taxonomy and fisheries biology.-Overall length:...
. The body is strongly dorsoventrally compressed and moderately wide. The head and nape are gently sloped to the insertion of the dorsal fin. The ventral surface of the fish is flat. The head contours are smooth. The eyes are small to medium. The caudal fin is slightly emarginate to forked, with the lower lobe longer than the upper lobe. The dorsal flap of the iris is present. The lips are wide and fairly thin; the upper lip has small, round papilla
Papilla (fish mouth structure)
The papilla, in certain kinds of fish, particularly rays, sharks, and catfish, are small lumps of dermal tissue found in the mouth, where they are "distributed uniformly on the tongue, palate, and pharynx"...
e and the lower lip has medium-sized papillae anteriorly and smaller ones posteriorly.
No morphometric
Morphometrics
Morphometrics refers to the quantitative analysis of form, a concept that encompasses size and shape. Morphometric analyses are commonly performed on organisms, and are useful in analyzing their fossil record, the impact of mutations on shape, developmental changes in form, covariances between...
, meristic
Meristics
Meristics is an area of ichthyology which relates to counting quantitative features of fish, such as the number of fins or scales. A meristic can be used to describe a particular species of fish, or used to identify an unknown species...
, or skeletal differences could be found among the species of Lasiancistrus. The only differences
between the species are the degree of abdominal plating (itself a characteristic that is likely to be very homoplastic) and coloration. L. schomburgkii has a body and fins with small white spots less than half the diameter of the plates (although spots may be faded); its plates are entirely dark or with small spots. L. saetiger has a body and paired fins with large white spots almost the same size as the plates, with the dorsal fin without spots; its plates are outlined in black. In the rest of the species, the dorsal fin is with black spots, the body is with dark markings and light markings, if present, are usually present as blotches or thick lines (except in the Bayano River population in Panama of L. caucanus); the body is never completely dark. In L. caucanus and L. tentaculatus, the abdomen lacks plates; between these two species, L. caucanus has whiskerlike odontodes on the corners of the snout in nuptial males and an emarginate caudal fin, while L. tentaculatus has tentacles along the anterior margin of the snout in nuptial males and a forked caudal fin. In the remaining two species, the abdomen has plates in at least a small patch medial to the insertion of the pectoral-fin spines; in L. heteracanthus, the abdomen has plates underneath entire pectoral girdle and on the abdomen, while in L. guacharote, the abdomen has only a couple of plates medial to insertion of pectoral-fin spines.