Sternarchorhynchus
From Wikipedia, the free encyclopedia
| Sternarchorhynchus | |
|---|---|
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| Sternarchorhynchus retzeri, conventional and X-ray images | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Gymnotiformes |
| Family: | Apteronotidae |
| Subfamily: | Apteronotinae |
| Genus: | Sternarchorhynchus Castelnau, 1855[1] |
| Type species | |
| Sternarchus (Rhamphosternarchus) mulleri, a synonym of Sternarchorhynchus oxyrhynchus Castelnau, 1855[1] | |
| Synonyms[1] | |
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Sternarchorhynchus is a genus of ghost knifefishes with a long, decurved snout that are found in river basins in tropical South America.[2]
Of the 32 recognized species, more than 2⁄3 are restricted to the Amazon basin (including the Tocantins system) in Bolivia, Brazil, Colombia, Ecuador and Peru, 7 species are found in river basins flowing into the Gulf of Paria in Colombia and Venezuela (mostly Orinoco system, but S. mendesi in Guanipa and San Juan), S. freemani is from the Essequibo basin in Guyana, S. galibi is from the Maroni basin in French Guiana and Suriname, and S. britskii is from the upper Paraná basin in Brazil.[3][4] There are records of Sternarchorhynchus from the Oyapock on the French Guiana–Brazil border, but their validity and taxonomic position is unclear.[3] Most species have relatively small ranges, but a few are more widespread. S. mormyrus of the Amazon and Orinoco basins is the only that occurs in more than one major river system.[3]
The habitat varies depending on species, but they require well-oxygenated waters.[3] They have been recorded in whitewater (like the Amazon River), blackwater (like Tefé River) and clearwater (like the Xingu River). Some species have been found in small streams, less than 0.5 m (1.6 ft) deep, while others inhabit the main stream of major rivers.[3] S. mesensis is known from both above-ground and below-ground habitats, but lacks the cavefish adaptions seen in the only true cave knifefish, Eigenmannia vicentespelaea. Some change habitat with age; adult S. cramptoni and S. mormyrus live in main river channels, but their young are found near the river shore in várzea.[3]
Nine species, all with small ranges in Brazil and most restricted to fast-flowing waters including rapids, are considered threatened by Brazil's Ministry of the Environment.[5][6] The current conservation status of S. gnomus is unclear, as the only known locality in Venezuela's lower Caroní basin has been flooded by a dam.[3]
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