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Pseudoplatystoma


Pseudoplatystoma is a genus of several South American catfish species of family Pimelodidae. The three species are known by a number of different common names. They inhabit the major rivers of north-eastern Argentina, Paraguay, Bolivia, Uruguay and Brazil. They prefer the main channels and tend to stay at maximum depth. They have robust bodies, and are important food fish.

Common names

In their native waters, these fish may be called Surubi in Spanish. P. corruscans may be called moleque or pintado. They often are referred to in the vernacular as Bagre rayado or Pintadillo (tiger catfish or tigershovelnose). P. corruscans, P. fasciatum, and P. tigrinum are also known as Spotted Sorubim, Barred Sorubim, and Tiger Sorubim, respectively. This genus contains the fish commonly known as the tiger shovelnose catfish in the aquarium hobby, though the species in this genus are relatively easy to confuse.

Taxonomy

Pseudoplatystoma is a monophyletic assemblage of catfishes.

P. fasciatum was the first species to be described, under the name Siluris fasciatus, by Carolus Linnaeus. In 1829, P. corruscans was described under the name Platystoma corruscans, and over a decade later P. tigrinum was described as Platystoma tigrinum. It was not until 1862 that Pseudoplatystoma was described and these species transferred to it, with P. fasciatum as type species.

Unrecognized species of Pseudoplatystoma have been included under the names P. fasciatum and P. tigrinum for decades. This genus traditionally contained only three species until 2007; there are currently eight species in this genus. P. punctifer, P. orinocoense, P. magdaleniatum, and P. reticulatum were formerly recognized as P. fasciatum, but are now recognized as distinct species. P. metaense is also now recognized as a distinct species from P. tigrinum.

Two clades are recognized within the genus. One is the P. fasciatum clade which includes P. fasciatum, P. punctifer, P. orinocoense, P. magdaleniatum, P. reticulatum, and P. corruscans. Within this clade, P. fasciatum and P. punctifer are sister species, and P. orinocoense is sister to the clade formed by these two species. The other, the P. tigrinum clade, includes only P. tigrinum and P. metaense. They are differentiated by anatomical characters.

The intergeneric relationships of this genus are well established. This genus forms a monophyletic group with Sorubim, Sorubimichthys, Hemisorubim, and Zungaro. Of these genera, Hemisorubim is most closely related to Pseudoplatystoma.

Distribution and habitat

The distribution of Pseudoplatystoma species includes the great river basins of South America: the Amazon, Orinoco, Parana, Sao Francisco, Magdalena, Rupununi, Essequibo, and Suriname River. They have not been reported from the Pacific basin. P. fasciatum inhabits the Guyana region, including the Essequibo and Suriname rivers and their tributaries, in the countries of Guyana, Suriname, and French Guiana. P. tigrinum is found in the Amazon River in Brazil, Colombia, Ecuador, Peru, and Venezuela. P. corruscans originates from the Parana River and Sao Francisco River in the countries of Argentina, Brazil, Paraguay, and Uruguay. P. orinocoense is named for and endemic to the Orinoco River of Venezuela. P. punctifer lives in the Amazon River in Bolivia, Brazil, Colombia, Ecuador, Peru, and Venezuela. P. metaense is distributed in the Orinoco River in Colombia and Venezuela; it is named for the Meta River, the type locality, a tributary of the Orinoco River. P. magdaleniatum is named for and endemic to the Magdalena River drainage, including the Cauca River of Colombia. P. reticulatum inhabits the central Amazon and Parana River in Argentina, Bolivia, Brazil, Paraguay, and Uruguay.

Pseudoplatystoma species live in a diverse range of habitats such as great rivers, lakes, side channels, floating meadows, and flooded forests. P. fasciatum is found in river beds and sometimes in flooded forests. Though it is biologically similar to P. tigrinum, this fish seems to favor shadier streams. P. tigrinum occurs in estuarine zones, mainly upstream of the first rapids up to the basin's headwaters. They live in the main bed of slow or fast zones, and the juveniles particularly live in flooded forests.

Physical characteristics

Pseudoplatystoma species are all large, boldly striped or spotted catfishes. They are familiar due to their distinctively marked color patterns. They are also recognized due to a depressed head, an occipital process extending backward to contact the predorsal plate, and a very long fontanel.

After gonadal maturation, females tend to grow faster than males. They have a large, depressed head with an expandable mouth. The eyes and teeth are small. They have dorsal and pectoral fin spines; in P. fasciatum, there is also an additional, smaller, dorsal spinelet preceding the dorsal spine. They exhibit typical barbels of catfish, the maxillary barbels sometimes being quite long, especially in juveniles.

P. fasciatum has 10–11 dark vertical bars that are relatively wider than other species of the Amazon, and there are fewer white vertical bars than dark ones; the pectoral fins and pelvic fins are darker with few or no spots; and the skull is at least 1/6th narrower than other species. It reaches a maximum of 90 centimetres TL.

P. tigrinum is distinguished by the presence of looplike bands connecting to, or extending to, dorsal region and continuing onto other side of body; looplike bars form cells. The adipose fin also has some loop-like bands and spots, but there are no discrete dark spots on the sides of the body. It reaches a maximum size of 130 cm TL.

P. corruscans has a body covered by large spots in six to eight eight rows with 4–13 pale vertical bars. The adipose fin contains 5–10 or no spots, the caudal fin has few spots. It reaches a maximum size of 114 cm TL.

P. orinocoense has straight, vertical bars on its body longer than those of P. faciatum and P. punctifer that extend to or connect dorsally. The bars of the anterior region extend below the dusky dorsolateral area. There are usually no spots below the lateral line, though some individuals may have two or three. It has a maximum recorded length of 49 cm TL.

P. punctifer has straight, dark, vertical bars with pale short lines; these bars do not connect across the dorsum on the opposite side. There are free discrete spots on below the laterla line. The adipose fin has fewer spots than P. fasciatum . It reaches a maximum length of 140 cm TL.

P. metaense has dark spots randomly distributed over the dusky region of its body; also, there are no more than five straight dark vertical bars on the side of the body. The adipose fin has fewer spots than in P. tigrinum . The pectoral and pelvic fins are pale without any dusky pigmentation. It has a maximum recorded length of about 53 cm TL.

P. magdaleniatum has wide, straight, dark vertical bars on its sides. There are no loops on the nape and associated areas. The pectoral fin has no spots, the dorsal fin has few or no spots, and the adipose has 6–7 large spots. It has a maximum recorded length of 100 cm .

P. reticulatum is named for its pattern; it has loop-like dark bars forming a reticulating pattern, never straight as in P. fasciatum, P. orinocoense, and P. punctifer. It has dark, looplike bars join those in the dorsal region of the body forming distinct cells. It also has longer looplike dark bars, extending far below the lateral line. The head shows either spots or loops. The anal fin is always with spots. The lower jaw is pointed. It has a maximum recorded length of about 60 cm TL.

Juvenile Pseudoplatystoma are quite different in appearance from adults. These fishes' juvenile coloration differs from their adult coloration, and the patterning is different. In the juvenile, the fish is dark on its back with an obvious boundary between the white of its sides and belly; also, the fish lacks stripes of P. fasciatum and P. tigrinum, but has spots instead. The adult colour is brown-olive, with about 13 or 14 dark transverse bands reaching up to the belly, which is white with a few dark spots.

Reproduction

Pseudoplatystoma are all migratory fish. P. orinocense and P. tigrinum make short migrations. At the end of the dry season, P. tigrinum can migrate at the same time as its prey, and then return at the end of the rainy season.

The migration of P. corruscans is heavily tied to flooding. As the rainfall occurs, there is the greates reproductive activity, highest rate of development of gonads, and the most amount of energy spent in migration.

Diet

These fish are nocturnal hunters. They are primarily piscivorous, feeding on fish such as electric knifefishes, cichlids, loricariids, and characins. They may consume on other fish such as sabalos, Prochilodus lineatus, and bogas, Leporinus obtusidens. Opportunistic feeders, they may also feed on crustaceans such as crabs or shrimps.

Relationship to humans

Pseudoplatystoma are of considerable economic value; all are sold in open fish markets throughout South America. They are important food fish for human consumption. P. fasciatum has a succulent yellowish flesh that is without bones. P. tigrinum is the most important catfish in gill-net fisheries of Guapore and Marmore rivers. These fish are being overexploited in their range, and it is possible that uncontrolled fishing has led to the disappearance of Pseudoplatystoma species in some local tributaries of the Amazon, Orinoco, and Magdalena. In the Argentine province of Entre Rios alone, about 27,000 tonnes of Pseudoplatystoma sp. are obtained every year, comprising 70 to 80% of the total capture there, mostly concentrated on the fishing area near the city of Victoria, opposite Rosario, Santa Fe.

The capture of P. corruscans has declined greatly due to changes in their environment. This fish has a high commercial value due to the excellent quality of its meat, its high marketability, and its marked participation in commercial fishing. Spawning of this fish can be induced with hormones and there is high potential for commercial production.

P. fasciatum and P. tigrinum are often found in public aquariums.

In the aquarium

Juvenile Pseudoplatystoma are marked as ornamental fish in both North and South America; however, they are usually at a size too small for certain identification, but more than one species may be imported. These species appear in the aquarium hobby, where they are most often sold under the name "tiger shovelnose" or "tiger shovelnose catfish". These fish prove to be hardy. However, the large adult size is problematic for both matters of housing as well as finding suitable tankmates that will not be consumed. With the appetite these fish have, finding enough good food may present some difficulty.

See also

List of freshwater aquarium fish species

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Pseudoplatystoma


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