Conspicuous brown first humeral spot, similar to somewhat diffuse, inverted triangle shape, width about four-five scales and depth of about five scales, two below and three above lateral line. Inconspicuous or faint second bar-shaped brownish humeral spot little behind first humeral spot, sometimes mixed with brown lateral stripe; pale or whitish anterior areas between and below humeral spots.
Black middle caudal rays, from 7 th to 11 th or 12 th , with its extremities included. Dorsal fin hyaline or translucent, blackish or not, on distal half of first three-five branched rays. Anal fin hyaline or translucent, with blackish ray tips. Caudal-fin lobes slightly blackish or translucent; middle caudal rays black. Adipose, pectoral, and pelvic fins hyaline, translucent or slightly blackish. Pupil with dark spot. Habitat and ecological notes. Astyanax xavante inhabits crystalline water streams with flow from 0.
There is a reduced number of pools along these watercourses, but there are many rapids and accentuated falls, some up to 30 m high. The bottom of the rapids is generally composed of stone and gravel-stone. Sand and small silt and clay fractions prevail at the bottom of the pools. In general, the rapids are typical of mountain streams with fast-flowing water and gravel, rocky, and sandy bottoms. The banks are covered by riparian forest which prevents most light penetration and have little or no marginal herbaceous vegetation.
There are many exposed roots from erosion and many tree trunks, branches and submerged leaves, in various stages of decomposition. The fishes preferentially occupy the water surface and the spaces among roots and branches. They usually form schools with up to two dozen individuals, but schools with about individuals have also been observed.
Astyanax xavante was collected about 0. Characidae , and Aequidens tetramerus Cichlidae , despite the reduced frequency of the latter. All the collections were conducted in the daytime. Astyanax xavante is an opportunistic omnivorous fish. Studies on the feeding ecology of this species have shown that from a total of examined stomachs, Other food items found in smaller proportions were Ostracoda crustaceans.
Filamentous algae were found in Fish scales were observed in 9. Studies conducted on fish specimens during the dry season July to October and flooded season February and March showed individuals in all stages of sexual maturity, except for the specimens collected on July 19, , when all individuals were ready for spawning. Fish ready for spawning were found in all collections, as well as many small, young specimens. The gonads, although mature, had a small number of oocytes compared to other mature fish. Thus, it seems evident that A. The highest percentages of sexually mature individuals occurred in the dry months.
The smallest mature male specimen had 26 mm SL; the smallest female, 25 mm SL. Hooks in the male fins were not seen in any reproductive phases. Geographical distribution. Serra Azul is located in the extreme south of the Serra do Roncador, at the beginning of the great Central Brazilian Plateau, whose direction is mainly south-north. The specific epithet xavante is a reference to the Xavante ethnic group, constituted by the natives inhabiting the Serra do Roncador and middle rio Araguaia, Mato Grosso, Brazil.
A noun in apposition. Astyanax xavante has the larger body depth in about two to three scales ahead of dorsal-fin origin, snout short but not abruptly tapered, and head not massive. These features are enough to distinguish it from species of the A. Most Astyanax species described more recently have restricted geographical distribution e.
Astyanax altiparanae and A. Restricted geographical distribution seems to occur also with A. Although numerous and extensive collections have been made in the middle rio Araguaia streams, A. The recent descriptions of the Astyanax species with restricted geographical distribution confirm that the genus is poorly known taxonomically, and this suggests that many species should be described with better collection efforts, especially in small headwater stream basins in areas that remain unexplored.
The stream where A. The creek possesses small water volume, and it is located in the mountain area. Approximately in the first m, i.
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The region is dominated by agriculture and cattle farms, and the region is presently suffering an anthropogenic impact, mostly by habitat destruction due to the increase in farmland. In the last years there have been frequent fires which swept the whole escarpment, destroying vast expanses of the cerrado habitat.
Environmental recovery is hindered by the high frequency of fires, which continuously expose the soil to erosion. As a consequence of this process, the riparian forest may disappear and its bottom will turn into sand, endangering the environment and affecting the survival of A. The size reached by Astyanax xavante is comparable to that of A. Melo, , A. Among the Astyanax species effectively recorded in the inventory of the vast drainage of Araguaia-Tocantins, A. Comparative material. Astyanax asuncionensis : FMNH , syntypes, 8, Astyanax goyacensis : MCZ , holotype, Astyanax novae : FMNH , type-series, 11, Astyanax scabripinnis : BMNH Langeani for the bony structure counts and suggestions on the manuscript, F.
Carvalho for the clearing and staining, M. Marinho for the photograph of the holotype, V. Oliveira for the help on the collections, V. Bertaco and two anonymous reviewers for the suggestions to improve the manuscript. The senior author is financially supported by the CNPq Proc. Bertaco, V.
Neotropical Ichthyology, 5 1 : Two new species of Astyanax Ostariophysi: Characiformes: Characidae from eastern Brazil, with a synopsis of the Astyanax scabripinnis species complex. Neotropical Ichthyology, 4 1 : Astyanax elachylepis , a new characid fish from the rio Tocantins drainage, Brazil Teleostei: Characidae. Neotropical Ichthyology, 3 3 : Description of two new species of Astyanax Teleostei: Characidae from headwater streams of Southern Brazil, with comments on the " A.
Ichthyological Exploration of Freshwaters, 12 3 : Britski, H. Peixes do Pantanal. Casciotta, J. Astyanax pampa Characiformes, Characidae , a new species from the southermost boundary of the Brazilian subregion, Argentina. Revue suisse de Zoologia, 2 : Eigenmann, C. The American Characidae. Memoirs of the Museum of Comparative Zoology, 43 3 : Memoirs of the Museum of Comparative Zoology, 43 4 Fink, W. The so-called cheirodontin fishes of Central America, with descriptions of two new species Pisces: Characidae. Smithsonian Contributions to Zoology, Garutti, V.rotasassfe.ga
Derek Chura (Author of The Last Astyanax)
Neotropical Ichthyology, 7 3 : xx-xx. Characoids of the World. Neptune City, T. Publications, p.
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Haluch, C. Lima, F. Brycon gouldingi , a new species from the rio Tocantins drainage, Brazil Ostariophysi: Characiformes: Characidae , with a key to the species in the basin. Ichthyological Exploration of Freshwaters, 15 3 : Lowe-McConnell, R. Ichthyological Exploration of Freshwaters, 2 1 : Melo, F. Arquivos do Museu Nacional, Astyanax henseli , a new name for Tetragonopterus aeneus Hensel, from southern Brazil Teleostei: Characiformes. Melo, C. Feeding habitats of fish from a stream in the savanna of Central Brazil, Araguaia Basin.
Neotropical Ichthyology, 2 1 : Santos, G. Souza, I.
Allopatric distribution in a small stream. These questions have fueled discussions on the relative importance of these different evolutionary mechanisms [ 12 , 17 , 27 — 31 ]. In order to analyze several of these issues such as the relative weight of selection, migration and genetic drift, it would be very useful to have accurate estimations of some demographic and population genetic parameters to describe the dynamic of cavefish evolution. Gene flow from the surface populations has been estimated to be from very low, if any, to very high, depending on the cave population examined.
Some studies have also found significant and higher gene flow from cave to surface populations than in the opposite direction [ 32 — 37 ]. Moreover, as some caves are very close to each other, fish migrations within cave clusters are likely.