Pseudolithoxus
Encyclopedia
Pseudolithoxus is a genus
of catfish
es (order
Siluriformes) 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.
. In 2001, the genus Pseudolithoxus was erected for these species. This group forms a monophyletic
sister group
to Lasiancistrus and Ancistrus
. P. anthrax and P. nicoi likely represent sister species. In 2011, P. kelsorum was described based on type material from Venezuela.
, Venezuela
in the upper Orinoco
, Ventuari
, Casiquiare
, and upper Negro rivers. P. anthrax ranges throughout the upper Orincoo, and is also found in the Caura River
and Aro River of Bolivar
state in Venezuela. P. dumus is known from the upper Orinoco, upper Negro, and Casiquiare River basins. Unlike its close relative P. anthrax, P. nicoi originates from the upper Negro River basin, including the Casiquiare basin. P. tigris inhabits the upper Orinoco and Ventuari River basin.
s (integumentary teeth) on elongated pectoral spines and along the snout margin, and 3 rows of plates on the caudal peduncle. In addition, it appears as if females as well as males develop hypertrophied snout and pectoral-fin odontodes, traits normally restricted to nuptial males in other loricariids.
Pseudolithoxus species may be differentiated based on colouration. Two species are black, usually with white spots, and lack dark bands on the caudal fin; P. nicoi has a white band at the distal
margin of the caudal fin, while P. anthrax does not. P. dumus has a colour pattern consisting of black spots on the head and anterior part of body, while P. tigris has a colour pattern consisting of brown and tan bars on the head and anterior part of body. However, P. dumus and P. tigris may actually both represent more species. In P. dumus, specimens from northern Amazonas have a well-spotted caudal peduncle, those from the Ventuari and Cataniapo Rivers have spots along the mid-line on the caudal peduncle, and those from the Casiquiare have spots combining to form bands on the caudal peduncle. In some P. tigris, though specimens have similar colour patterns, they may differ in thickness of the tan bars and dark bars, body depth, and eye position.
The body of these fish is very dorsoventrally flattened with both ventral- and dorsal-surface flat. The dorsal fin spine is weak, and the dorsal fin spinelet supports odontodes. The pectoral fins are usually elongated, reaching the anus in juveniles and growing to the anal fins in the adults; P. anthrax has been referred to as "flying catfish", probably due to these long pectoral fins in adults. The caudal fin is weakly forked, with the lower lobe longer than the upper. The eyes are mostly dorsal. The abdomen is without plates.
Pseudolithoxus species are known to grow to about 9.4–12.4 centimetres (3.7–4.9 in) SL
. P. tigris probably matures at a relatively small size; in a specimen about 5 cm (2 in) SL, the snout and pectoral-fin spine odontodes are already greatly elongated, while the odontodes are only beginning to develop in similarly sized specimens of other species.
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 five species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, P. anthrax, P. dumus, P. kelsorum, P. nicoi, and P. tigris, previously described as the Lasiancistrus
Lasiancistrus
Lasiancistrus is a genus of catfishes of the family Loricariidae. It includes six species, L. caucanus, L. guacharote, L. heteracanthus, L. saetiger, L. schomburgkii, and L. tentaculatus.-Taxonomy:...
anthrax group.
Taxonomy
The species group was originally described in 2000 and the four species were temporarily placed in LasiancistrusLasiancistrus
Lasiancistrus is a genus of catfishes of the family Loricariidae. It includes six species, L. caucanus, L. guacharote, L. heteracanthus, L. saetiger, L. schomburgkii, and L. tentaculatus.-Taxonomy:...
. In 2001, the genus Pseudolithoxus was erected for these species. This group forms a 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...
sister group
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
to Lasiancistrus and 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...
. P. anthrax and P. nicoi likely represent sister species. In 2011, P. kelsorum was described based on type material from Venezuela.
Distribution
Most species are restricted to AmazonasAmazonas (Venezuelan state)
Amazonas State is one of the 23 states into which Venezuela is divided.The state capital is Puerto Ayacucho. The capital until the early 1900s was San Fernando de Atabapo. Although named after the Amazon River, most of the state is drained by the Orinoco. Amazonas State covers a total surface...
, 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...
in the upper 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...
, Ventuari
Ventuari River
The Ventuari River is a river in the Orinoco basin in Venezuela. The Ventuari flows from eastern Venezuela in the Guiana Highlands southwest into the Orinoco River. It is 520 km long and its major tributary is the Manapiare River.-References:...
, Casiquiare
Casiquiare canal
The Casiquiare river is a distributary of the upper Orinoco flowing southward into the Rio Negro, in Venezuela, South America. As such, it forms a unique natural canal between the Orinoco and Amazon river systems. It is the largest river on the planet that links two major river systems, a...
, and upper Negro rivers. P. anthrax ranges throughout the upper Orincoo, and is also found in the Caura River
Caura River (Venezuela)
The Caura is a tributary of the Orinoco River, located in Bolívar State in Venezuela. Its flow is the second after the Caroni River among the affluents of the Orinoco River, with almost 3.000 m³/s....
and Aro River of Bolivar
Bolívar (state)
Bolívar State , is one of the 23 states into which Venezuela is divided. The state capital city is Ciudad Bolívar. Bolívar State covers a total surface area of 238,000 km² and in June 30, 2010 had an estimated population of 1,620,359....
state in Venezuela. P. dumus is known from the upper Orinoco, upper Negro, and Casiquiare River basins. Unlike its close relative P. anthrax, P. nicoi originates from the upper Negro River basin, including the Casiquiare basin. P. tigris inhabits the upper Orinoco and Ventuari River basin.
Description
Pseudolithoxus species are characterized by evertible cheek plates, a very dorsoventrally flattened body, extremely hypertrophied 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 (integumentary teeth) on elongated pectoral spines and along the snout margin, and 3 rows of plates on the caudal peduncle. In addition, it appears as if females as well as males develop hypertrophied snout and pectoral-fin odontodes, traits normally restricted to nuptial males in other loricariids.
Pseudolithoxus species may be differentiated based on colouration. Two species are black, usually with white spots, and lack dark bands on the caudal fin; P. nicoi has a white band at the distal
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
margin of the caudal fin, while P. anthrax does not. P. dumus has a colour pattern consisting of black spots on the head and anterior part of body, while P. tigris has a colour pattern consisting of brown and tan bars on the head and anterior part of body. However, P. dumus and P. tigris may actually both represent more species. In P. dumus, specimens from northern Amazonas have a well-spotted caudal peduncle, those from the Ventuari and Cataniapo Rivers have spots along the mid-line on the caudal peduncle, and those from the Casiquiare have spots combining to form bands on the caudal peduncle. In some P. tigris, though specimens have similar colour patterns, they may differ in thickness of the tan bars and dark bars, body depth, and eye position.
The body of these fish is very dorsoventrally flattened with both ventral- and dorsal-surface flat. The dorsal fin spine is weak, and the dorsal fin spinelet supports odontodes. The pectoral fins are usually elongated, reaching the anus in juveniles and growing to the anal fins in the adults; P. anthrax has been referred to as "flying catfish", probably due to these long pectoral fins in adults. The caudal fin is weakly forked, with the lower lobe longer than the upper. The eyes are mostly dorsal. The abdomen is without plates.
Pseudolithoxus species are known to grow to about 9.4–12.4 centimetres (3.7–4.9 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:...
. P. tigris probably matures at a relatively small size; in a specimen about 5 cm (2 in) SL, the snout and pectoral-fin spine odontodes are already greatly elongated, while the odontodes are only beginning to develop in similarly sized specimens of other species.