Two new tetras named

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Scientists have described two colourful new species of tropical fish from the tetra genus Hyphessobrycon.

Tiago Carvalho and Vinicius Bertaco of Pontificia Universidade Catolica do Rio Grande do Sul described the two new characin species as Hyphessobrycon melanostichos and H. notidanos in a paper in the latest issue of the journal Neotropical Ichthyology.

Both species are known only from the Rio Doze de Outubro, a tributary of the Rio Juruena in the upper reaches of the Rio Tapajos, Chapada dos Parecis, Comodoro, Mato Grosso, Brazil.

Hyphessobrycon melanostichos, which gets its name from the Greek for black line, has a broad black longitudinal stripe running from the middle of the eye to the middle of the tail, as well as an elongated spot in the humeral region near the base of the pelvic fin. The chest, tail and unpaired fins are red in colour.

A similar vertically elongate humeral spot is also seen in H. notidanos, a yellow and red species species in which the males develop an elongated dorsal fin. Like melanostichos, this species also has a longitudinal stripe but has much brighter colouration, with a deep red colour to the entire bottom half of the fish in males.

Carvalho and Bertaco wrote: "Two new species of Hyphessobrycon are described from the upper rio Tapajos basin, Mato Grosso, Brazil. Hyphessobrycon melanostichos is distinguished from its congeners by the combination of a conspicuous longitudinal broad black band beginning on the posterior margin of orbit and reaching the tip of middle caudal fin rays, a distinct vertically elongate humeral spot, and 16 to 18 branched anal-fin rays.

"Hyphessobrycon notidanos is distinguished from its congeners by the combination of an elongate dorsal fin in mature males, a vertically elongate humeral spot, 2-4 maxillary teeth, iii,8 dorsal-fin rays, and 16 to 21 branched anal-fin rays."

The two new tetras were first discovered in July 2004 duing an expedition to sample fishes in a number of the Amazon's right-bank tributaries, including the Rio Tapajos, Rio Madeira and Rio Purus. Carvalho and Bertaco said that they found an especially diverse range of species in the collections from the Rio Juruena, one of the upper Rio Tapajos tributaries, from where the two new Hyphessobrycon were found. They believe that this part of the Amazon basin has an unrecognised area of endemism, with many species occurring here and nowhere else:

"During the Transcontinental Expedition (TCE) several tributaries of the rio Tapajos, rio Madeira, rio Purus and rio Paraguay basins were sampled. Hyphessobrycon melanostichos and H. notidanos were collected only in the rio Doze de Outubro, a tributary of the rio Juruena, upper rio Tapajos basin.

"The occurrence of these two new species, along with Hyphessobrycon hexastichos, Hemigrammus skolioplatus, Hasemania sp. n. Bertaco & Malabarba (in press), Bryconamericus sp. n. J. Pezzi da Silva (pers. comm.) (Characidae); Ancistrus parecis Fisch-Muller et al. (2005); a new genus of Ancistrinae (Loricariidae) and a new species of Cetopsorhamdia (Heptapteridae) R. Reis (pers. comm.) suggest that this portion of rio Tapajos basin formed by the rivers in the Chapada dos Parecis Formation draining to rio Juruena has an apparently endemic ichthyofauna that differs from other rivers of the east bank of the Amazon or even from the rio Arinos and rio Teles Pires basins, both also tributaries of the rio Tapajos. Further extensive studies on the composition of the fish fauna will be necessary to corroborate or not the delimitation of this area of endemism."

For more information on the new tetras see the paper: Carvalho TP and VA Bertaco (2006) - Two new species of Hyphessobrycon (Teleostei: Characidae) from upper Rio Tapajos basin on Chapada dos Parecis, Central Brazil. Neotropical Ichthyology, Vol. 4, No. 3, pp 301-308.