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The arapaima, Arapaima gigas, is a fish whose populations are threatened by both overfishing and the ongoing destruction of its natural habitats. In the Amazon basin, varying levels of population structure have been found in A. gigas, although no data are available on the genetic diversity or structure of the populations found in the Araguaia-Tocantins basin, which has a topographic profile, hydrological regime, and history of fishing quite distinct from those of the Amazon. In this context, microsatellite markers were used to assess the genetic diversity and connectivity of five wild A. gigas populations in the Araguaia-Tocantins basin. The results of the analysis indicated low levels of genetic diversity in comparison with other A. gigas populations, studied in the Amazon basin. The AMOVA revealed that the Arapaima populations of the Araguaia-Tocantins basin are structured significantly. No correlation was found between pairwise FST values and the geographical distance among populations. The low level of genetic variability and the evidence of restricted gene flow may both be accounted for by overfishing, as well as the other human impacts that these populations have been exposed to over the years. The genetic fragility of these populations demands attention, given that future environmental changes (natural or otherwise) may further reduce these indices and eventually endanger these populations. The results of this study emphasize the need to take the genetic differences among the study populations into account when planning management measures and conservation strategies for the arapaima stocks of the Araguaia-Tocantins basin.

The genetic diversity of the specimens of four natural populations of Arapaima from Araguaia-Tocantins basin was assessed within and among these stocks, using five primers for ISSR. COI (cytochrome c oxidase subunit I ) partial sequences confirmed that the specimens belongs to Arapaima gigas . The ISSR provided 168 loci, of which 165 were polymorphic. However, the number of loci for each population and expected heterozygosity values were low. AMOVA showed 52.63% intra-population variation and 47.37% inter-population variation. The F ST was high among all populations (F ST ≥ 0.25), however, the cluster analysis (PCoA) and Bayesian inference showed three major groups: Araguaiana-MT + São Félix do Araguaia-MT, Novo Santo Antônio-MT and Itupiranga-PA. The genetic distance was not correlated with geographical distance. The ISSR marker revealed that the populations of the Araguaia-Tocantins are structured and have a low genetic diversity. These are the first data from a population analysis using molecular markers for A. gigas of Araguaia-Tocantins basins and may be used to define the best management strategies and conservation projects for this species. A diversidade genética dos espécimes de quatro populações naturais de Arapaima coletados na bacia do Araguaia-Tocantins foi avaliada com base em cinco primers para marcadores moleculares ISSR. A sequência parcial do COI (cytochrome c oxidase subunit I ) confirmou que os espécimes pertencem à espécie Arapaima gigas . Os ISSR forneceram 168 loci , dos quais 165 polimórficos. No entanto, para cada população, os valores de heterozigosidade esperada foram baixos. A AMOVA mostrou 52,63% de variação intrapopulacional e 47,37% interpopulacional. O F ST foi alto entre todas as populações (F ST ≥ 0,25); entretanto, a análise de agrupamento e a inferência Bayesiana mostraram três grandes grupos: Araguaiana-MT + São Félix do Araguaia-MT, Novo Santo Antônio-MT e Itupiranga-PA. A distância genética não teve correlação com a distância geográfica. Os ISSRs se mostraram eficientes para determinar a diversidade genética para a A. gigas , revelando que as populações da bacia Araguaia-Tocantins estão estruturadas e com baixa diversidade genética. Estes são os primeiros dados de análise populacional utilizando ISSR para A. gigas da bacia Araguaia-Tocantins e poderão ser utilizados para definir as melhores estratégias de manejo e projetos de conservação dessa espécie.

Made available in DSpace on 2014-09-30T18:18:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-09-01Bitstream added on 2014-10-01T14:03:23Z : No. of bitstreams: 1 S1679-62252013000300553.pdf: 3110218 bytes, checksum: 6f72fb2327f81d8fb8d575435b161a41 (MD5) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundacao de Amparo a Pesquisa do Estado de Mato Grosso (FAPEMAT) SEMA Instituto Brasileiro do Meio Ambiente e Recursos Naturais Renovaveis (MMA/IBAMA) Astyanax é um grupo bastante diverso de peixes neotropicais cujas diferentes formas ocupam distintos ambientes. Esta grande variabilidade também se reflete em aspectos citogenéticos e moleculares, que têm sido repetidamente demonstrados por meio de estudos citogenéticos. A fim de caracterizar o cariótipo de representantes deste gênero, seis espécies foram estudadas: Astyanax altiparanae, A. elachylepis, A. xavante, A. argyrimarginatus e duas espécies novas provisoriamente citadas como Astyanax sp. e A. aff. bimaculatus. Um estudo citogenético detalhado com base na coloração convencional com Giemsa, AgNORs, banda C, fluorocromos base-específicos, e FISH com sondas para genes ribossomais 18S e 5S foi realizado com o objetivo de compreender alguns dos mecanismos cromossômicos associados com a alta diversificação que caracteriza este grupo de peixes e que culminou com o estabelecimento dessas espécies. Os resultados revelaram 2n = 50 cromossomos para cinco espécies e 2n = 52 cromossomos para Astyanax sp. Pequenas variações na macroestrutura dos cariótipos foram identificadas e se mostraram relevantes quando analisadas com base nos bandamentos clássicos, coloração por fluorocromos base-específicos e FISH com sondas de DNA 18S e 5S. Esssa diversidade cariotípica detectada indica a necessidade de uma revisão taxonômica no grupo de indivíduos aqui referidos como A. aff. bimaculatus, inclusive com a descrição de Astyanax sp., incluindo a possibilidade de inserção dessa unidade em outro gênero distinto de Astyanax. Astyanax is a diverse group of Neotropical fishes, whose different forms occupy different environments. This great diversity is also reflected on cytogenetic aspects and molecular markers, which have repeatedly been demonstrated by cytogenetic studies. In order to characterize the karyotype of species of this genus, six species were studied: Astyanax altiparanae, A.argyrimarginatus, A. elachylepis, A. xavante, and two new species provisionally called Astyanax sp. and A. aff. bimaculatus. A detailed cytogenetic study based on conventional staining with Giemsa, AgNORs, C-banding, base-specific fluorochromes, and FISH using ribosomal genes 18S and 5S was conducted, aiming to understand some of the chromosomal mechanisms associated with the high diversification that characterizes this group and culminated with the establishment of these species. The results showed 2n = 50 chromosomes for five species and a karyotype with 52 chromosomes in Astyanax sp. Small variations in the macrostructure of the karyotypes were identified, which were quite relevant when analyzed by classical banding, fluorochromes, and FISH methods. These differences among Astyanax spp. (2n = 50) are largely due to changes in the amount and types of heterochromatic blocks. Astyanax sp (2n = 52), in addition to variations due to heterochromatic blocks, has its origin possibly by events of centric fission in a pair of chromosomes followed by minor rearrangements.These results show an interesting karyotypic diversity in Astyanax and indicate the need of a review of the group referred as A. aff. bimaculatus and the description of Astyanax sp., including the possibility of inclusion of this unit in another genus. Universidade Federal de Mato Grosso Laboratorio de Genetica e Citogenetica de Peixes Universidade Federal de Santa Catarina Departamento de Biologia Celular, Embriologia e Genetica Universidade Estadual Paulista Julio de Mesquita Filho Instituto de Biociencias Laboratorio de Biologia e Genetica de Peixes Universidade Estadual Paulista Julio de Mesquita Filho Instituto de Biociencias Laboratorio de Biologia e Genetica de Peixes CNPq: 474057/2009-8 FAPEMAT: 453511/2009 FAPEMAT: 841147/2009 SEMA: 104358/2011 MMA/IBAMA: 15226-1