ESTUDO DA VARIABILIDADE GENÉTICA DO CARDINAL (OSTARIOPHYSI: CHARACIFORMES: Paracheirodon axelrodi) NA BACIA DO RIO NEGRO

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

The cardinal tetra Paracheirodon axelrodi is the most exported Amazonian characin. Since the mid-1950s, cardinal tetras have been harvested along their natural distribution in the Negro, and the upper Orinoco River drainages and their tributaries in Brazil, Colombia and Venezuela. Just the cardinal tetra constitutes over 80% of total catch all ornamental fish exported from the Amazon region. Despite its economic importance, no fisheries management or conservation plans are available for the ornamental fishes in the Amazon. As part of an effort to develop hypervariable molecular markers for Amazonian fishes and to contribute genetic information for future management and conservation plans, microsatellite loci were developed for the cardinal tetra (Paracheirodon axelrodi) and additional previously published microsatellites were assayed. Starting from a protocol of enrichment for microsatellite repeat regions and selective hybridization by using oligonucleotides as a probe, a total of 12 microsatellites loci were developed and characterized. Although five out of 12 loci were polymorphic, only two were adequate for population analyses purposes. By using six previously published microsatellite loci, the genetic structure of P. axelrodi from six wild populations collected in distinct years in the municipalities of Barcelos (Igarapé Cajarizinho, Igarapé Zamula and Lago Rainha) and Santa Izabel do Rio Negro (Rio Tea, Rio Urubaxi and Igarapé Iaha) was investigated. Polymorphism at all loci was assessed, with a total of 17 different alleles found. These microsatellites markers detected substantial amounts of genetic variation, with observed heterozygosity (Ho) ranging from 0,1 to 0,967 and the expected heterozygosity (He) ranging from 0.059 to 0.938. The most loci were at HardyWeinberg equilibrium (HWE) but in some cases deviations were observed. Also, partial evidences for linkage disequilibrium was detected. Overall, the populations were characterized by high microsatellite genetic diversity (d= 0,744) and a low genetic structure (FST = 0,14309) which may be reversed or minimized by the estimated gene flow (Nm =1-9). It was suggested that the Negro River did not hinder dispersal of the cardinal tetra and that sampled populations are a single unit of management. Mantels test showed no correlation between genetic distance and geographical distance for the populations sampled in 1999 but did show a weak but significant correlation for the 2005 samples. The detection of bottlenecks gave different results for the tests implemented in the programs Bottleneck and Mvalues; genetic bottleneck was observed only in the second test and only in some populations. In conclusion, it was found that the cardinal tetra in the middle Negro River is not immediately threatened by loss of evolutionary potential either due to long term events, i.e. extrativism fisheries, or by short term events, i.e. the cyclic El Niño.

ASSUNTO(S)

microssatélites variabilidade genética genetica peixe ornamental

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