Isolamento e caracterização de locos microssatélites e sua aplicação na identificação de estoque pesqueiro da piraíba - Brachyplatystoma filamentosum – Pimelodidae-Siluriformes

Abstract

The Piraíba- Brachyplatystoma filamentosum, Is the largest among the migratory Amazonian catfish. Its distribution covers the entire Amazon basin, from the rivers of Amapá to the Andes, living both in white water, black and clear, as well as in tributaries and floodplains and igapó lakes. Until 2005 the information about this species were treated in common with Brachyplatystoma capapretum, which was described based on osteological features. In this context, it is necessary studies on the biology of the species, being the genetics the promising science to elucidate issues such as life cycle, accurate distribution in the Amazonian environment, variability and genetic stock. Genetic studies using mitochondrial DNA sequences contributed revealing that on average B. filamentosum is more abundant than B. capapretum in white water rivers in the Amazon basin. This study aims, through microsatellite markers, check if B. filamentosum presents population structure and can compose more than one genetic stock, if it has genetic segregation and if it is associated with the type of water where is its natural environment. Seventeen microsatellite markers were isolated and characterized in 35 individuals of B. filamentosum coming from the Belem - PA, Brazil. There were obtained 78 alleles that ranged from 1 to 15 alleles per locus, with an average of 6.00%. The observed heterozygosity (Ho) and expected (He) ranged from 0.100 to 0.875 (mean 0.569) and 0.136 to 0.837 (mean 0.558), respectively. The heterologous amplification resulted in 3 to 12 locos of six species of the genus Brachyplatystoma B. capapretum (black piraíba), B. vaillantii (piramutaba), B. rousseauxii (dourada) B. platynemum (Babão), B. tigrinum (dourada zebra ) and B. juruense (Flamengo). The microsatellite markers obtained will contribute to future genetic studies of natural populations of B. filamentosum and will be available for other species of the genus Brachyplatystoma. Ten microsatellite loci were used for population genetic analyzes of 178 individuals of B. filamentosum sampled in six regions of the Amazon basin, representatives of three different types of water. A total of 80 alleles was obtained with average of 8 alleles, the average of heterozygosity observed and expected from 0.548 to 0.598 per locus. The results of AMOVA showed moderate genetic flow between locations and significant values of FST. It is not possible accept the null hypothesis of panmixia, from single stock for the species, because the analyzes indicate structure between some locations, especially between Araguaia River with Branco River (FST = 0.113) and Negro River (FST = 0.219). The Negro River also presented the Madeira River (FST = 0.101). The Nm values were also below 4 between these locations. Thus, it is suggested that B. filamentosum be considered as a single genetic stock, especially in Negro River, Araguaia River and Branco River. However, it is not possible to say that this segregation is fully associated with the type of water.