A new Astyanax tetra has been named from the middle Araguaia River drainage in a recent issue of the journal Neotropical Ichthyology.
Authors Valdener Garutti and Paulo Venere named the new species, Astyanax xavante, and say it has two vertically elongate humeral spots, a brown stripe on flank and a black spot on middle caudal-fin rays.
According to the authors, the new species, which is named after the native tribe inhabiting the middle Araguaia drainage, inhabits crystalline water streams with flow from 0.05 to 0.70 m3/s.
The fishes preferentially occupy the water surface and the spaces among roots and branches, usually forming schools of up to two dozen individuals (although groups of about 150 individuals have also been observed).
Astyanax xavante is an opportunistic omnivorous fish, with stomach contents of fishes examined consisting primarily of invertebrate and plant remains.
The species can be told apart from other Astyanax by the presence of 34–37 lateral-line scales; body depth 35.5–40.2% standard length; head length 28.4-31.2% standard length; distance from snout to origin of dorsal fin 50.0-56.0% standard length; interorbital width 34.5-39.4% head length; 23–26 anal-fin rays, of which 19–23 are branched; one to three maxillary teeth; five tetra- to heptacuspidate premaxillary inner row teeth, four, large, penta- to heptacuspidate, and four to nine, small uni-, bi-, tri- or pentacuspid, dentary teeth; snout not abruptly tapered; anal-fin origin on vertical through posterior third of dorsal-fin base; mature males without fin ray hooks.
For more information, see the paper: Garutti, V and PC Venere (2009) Astyanax xavante, a new species of characid from middle rio Araguaia in the Cerrado region, Central Brazil (Characiformes: Characidae). Neotropical Ichthyology 7, pp. 377–383.