Scientists have described a new species of Knodus tetra from the upper Rio Negro system in Brazil.
Katiane Ferreira and Flavio Lima described the new characin as Knodus tiquiensis in a paper in the latest issue of the journal Copeia.
Knodus tiquiensis was discovered in the Rio Tiquie, a tributary of the Rio Uaupes in the upper Rio Negro system of Brazil's Amazon basin.
The silvery-grey tetra has yellowish pectoral fins, and a white anterior portion on the anal fin and outer parts of the pelvic fins.
Ferreira and Lima say that the new Knodus can be distinguished from other members of the genus by the presence of thickened skin, which forms folds that cover the basal portion of the front six branched anal-fin rays and interradial membrane.
The six branched rays are also considerably thicker than other rays.
The tetra is rheophilic and lives only in areas of moderate to strong current, including the torrential flows around waterfalls.
It feeds on chironomid larvae and reaches a size of around 6cm/2", according to the type series.
The species is said to be widespread in the upper Rio Tiquie, and occurs above large waterfalls, such as the Cachoeira do Caruru, Cachoeira da Pedra Curta, and Cachoeira Comprida.
Local fishermen told the authors that the species occurs along the length of the rivers, all the way up to the headwaters in Estado Vaupes in Colombia.
Other species described from the area include Corydoras tukano (view map) and Jupiaba poekotero.
For more information see the paper: Ferreira KM and FCT Lima (2006) - A new species of Knodus (Characiformes: Characidae) from the Rio Tiquie, upper Rio Negro system, Brazil. Copeia, 2006(4), pp. 630-639.