Genetic variability of two Nile tilapia strains by microsatellites markers

O objetivo desse trabalho foi avaliar a variabilidade genética de duas variedades de tilápia nilótica (Oreochromis niloticus), Chitralada e Red Stirling, e de suas progênies submetidas a programas de melhoramento genético, em sistemas intensivos de cultivo por meio de marcadores microssatélites. Foram utilizados 30 animais de cada variedade parental, 30 animais híbridos (CH), provenientes do cruzamento entre as variedades Chitralada e Red Stirling, e 30 animais (RR) provenientes do cruzamento entre os parentais da variedade Red Stirling. Utilizaram-se cinco microssatélites: UNH104, UNH108, UNH118, UNH222 e UNH231. Observaram-se baixos índices de endogamia, com valores de FIS negativo para as duas variedades e seus cruzamentos. Verificou-se diferença genética entre as duas variedades, obtida pelo cálculo do índice de fixação de alelos (FST = 0,131 e RST = 0,130). As variedades parentais Chitralada e Red Stirling apresentaram 24,4% de distância genética, o que se refletiu na presença de vigor híbrido com 23,5% de incremento em rendimento no plantel CH.The objective of this work was to evaluate the genetic variability of two Nile tilapia strains (Oreochromis niloticus), Chitralada and Red Stirling, as well as its offsprings submitted to genetic enhancement programs, in intensive systems farming by microsatellites markers. Thirty individuals of each parental strain, 30 crossbred (CH) individuals from Chitralada and Red Stirling strains, and 30 individuals from Red Stirling progeny (RR) were used. Five microsatellites loci were utilized: UNH104, UNH108, UNH118, UNH222 e UNH231. Low values of inbreeding were observed with a negative FIS in both strains and their crossings. Genetic differences between the two strains were detected through FST = 0.131 and RST = 0.130. The parental strains Chitralada and Red Stirling presented 24.4% of genetic distance, which produced 23.5% of hybrid vigor in the CH stock

Broad Geographic Distribution of Roundscale Spearfish (Tetrapturus georgii) (Teleostei, Istiophoridae) in the Atlantic Revealed by DNA Analysis: Implications for White Marlin and Roundscale Spearfish Management

The recent validation of the roundscale spearfish (Tetrapturus georgii) within the western North Atlantic has introduced new complexities in the management of the overfished white marlin (Kajikia albida) in this region due to historical and contemporary misidentification between the two morphologically similar species. Compounding the management challenge for white marlin, which is currently assessed as a single Atlantic-wide stock, is an unclear picture of the extent of the roundscale spearfish\u27s overall Atlantic distribution. By using genetic tools (mitochondrial DNA ND4L-ND4 locus sequences) for species identification, we confirm that the roundscale spearfish has a much broader distribution than previously known, including the central North Atlantic and much of the western South Atlantic to at least 28°52′S. This much wider Atlantic distribution of the roundscale spearfish sympatric with its morphologically similar congeners, the white marlin and longbill spearfish (Tetrapturus pfluegeri), raises further management complexities: it increases the geographic scale for species misidentification in catch records that form the basis for stock assessments and uncertainty in currently accepted white marlin biological parameters. Additional vigilance in obtaining accurate species identification by improved fishery onboard observer training and incorporation of genetic tools is recommended for informing management of white marlin, longbill spearfish and roundscale spearfish throughout the Atlantic

Large-scale SNP discovery and construction of a high-density genetic map of Colossoma macropomum through genotyping-by-sequencing

Colossoma macropomum, or tambaqui, is the largest native Characiform species found in the Amazon and Orinoco river basins, yet few resources for genetic studies and the genetic improvement of tambaqui exist. In this study, we identified a large number of single-nucleotide polymorphisms (SNPs) for tambaqui and constructed a high-resolution genetic linkage map from a full-sib family of 124 individuals and their parents using the genotyping by sequencing method. In all, 68,584 SNPs were initially identified using minimum minor allele frequency (MAF) of 5%. Filtering parameters were used to select high-quality markers for linkage analysis. We selected 7,734 SNPs for linkage mapping, resulting in 27 linkage groups with a minimum logarithm of odds (LOD) of 8 and maximum recombination fraction of 0.35. The final genetic map contains 7,192 successfully mapped markers that span a total of 2,811 cM, with an average marker interval of 0.39 cM. Comparative genomic analysis between tambaqui and zebrafish revealed variable levels of genomic conservation across the 27 linkage groups which allowed for functional SNP annotations. The large-scale SNP discovery obtained here, allowed us to build a high-density linkage map in tambaqui, which will be useful to enhance genetic studies that can be applied in breeding programs

Conservation genetics of tilapias: Seeking to define appropriate units for management

Tilapias comprise 112 species and subspecies of cichlid fishes of the genera Oreochromis, Sarotherodon, and Tilapia. Because of the importance of tilapias to aquatic ecosystem structure and function, fisheries, and aquaculture, it is critically important to conserve wild genetic resources. Of the 112 recognized tilapia taxa, 41 are regarded as imperiled. In order to manage adaptively important genetic variation in tilapias, we need to recognize and define biologically appropriate units of conservation. An evolutionary significant unit (ESU) can be defined as a population or group of populations that merits priority for conservation and separate management because of high genetic and ecological distinctiveness from other such units. Management units (MUs) are defined as populations that are demographically independent of one another; that is, their population dynamics depend mostly on local birth and death rates, and not on genetically effective migration. Identification of MUs – similar to “stocks” widely referred to in fisheries management – is useful for short-term management, such as managing habitat, delineating fishing areas, setting harvest rates, and monitoring population status. Against this background, the goal of our review and synthesis was to summarize knowledge and recommend critical work yet to be done regarding conservation of tilapias, approaching this task in a species-by-species manner. With the exceptions of Oreochromis niloticus, O. mossambicus, and Sarotherodon melanotheron, the body of existing work regarding genetic and adaptive differentiation of populations of tilapias is insufficient to inform identification of evolutionary significant units, a knowledge gap that should be addressed by targeted research. We note that competition and interspecific hybridization caused by introductions of tilapias for aquaculture purposes jeopardizes the genetic resources of certain native tilapia species. We hope that our review and synthesis spark critical discussion of tilapia conservation within the tilapia aquaculture, management, and conservation communities

Diversidade genetica do DNA mitocondrial em populações cultivadas e selvagens da Pirapitinga-do-Sul, Brycon opalinus (Cuvier, 1819) (Characiforme, Characidae, Bryconiae), na Bacia do Paraíba do Sul

Orientadores: Jose Eduardo Krieger, Marta Helena KriegerTese (doutorado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: A diversidade do DNA mitocondrial pelo RFLP (Restriction Fragment Length Po/ymorphism) foi usada para investigar a estrutura genético populacional, e avaliar o potencial desta metodologia para identificação e manejo das populações cultivadas e selvagens da Pirapitinga-do-sul ¿ Brycon opalinus (Cuvier, 1819) (Characiforme, Characidae, Bryconiae) na bacia do Paraíba-do-sul. Amostras de DNA de 283 indivíduos, provenientes de 7 rios da bacia do Paraíba-do-Sul e da Estação de Hidrobiologia e Aqüicultura de Paraibuna (CESP), foram analisadas pela hibridação com sondas mitocondriais homólogas. De um total de 24 enzimas de restrição, 6 foram selecionadas (Apa .l, Ava ll, EcoR I, Hinc ll, Hpa I, Nhe I) por produzirem polimorfismo, as quais resultaram em 27 haplótipos mitocondriais. o DNA mitocondrial da espécie em estudo apresentou um tamanho de 16,300 (± 500) pb. Heteroplasmia de tamanho da molécula não foi observada, porém, em 17.5% dos animais da Estação de Hidrobiologia e Aqüicultura de Paraibuna (CESP ), 2.7% do rio Negro e 15.79% do rio do Peixe o fenômeno da heteroplasmia de sítio de restrição com a enzima Nhe I foi observado. Dois haplótipos (25 e 26) foram encontrados exclusivamente nos indivíduos da Estação. Desta forma, em razão da transmissão materna do DNA mitocondrial esses dois haplótipos podem ser considerados como marcadores potenciais para avaliar a sobrevivência e sucesso reprodutivo de peixes introduzidos em projetos de repovoamento. A diversidade haplotípica dos animais mantidos em cativeiro foi relativamente alta (h=0.75), e a das populações selvagens foi de h=0.62. A diversidade nucleotídica média entre os 27 haplótipos encontrados para o Brycon opalinus foi de 0.825%. A análise da variância molecular (AMOVA Analysis of MOlecular V Ariance) apresentou maior percentagem de variância nucleotídica dentro das populações (70.02%). Contudo, 15.97% da variância foi observada entre populações Estes índices possibilitaram avaliar a condição atual do estoque de reprodutores mantidos em cativeiro, e utilizado na produção de alevinos para o repovoamento. Em conjunto, estes dados permitiram analisar a estruturação genética da espécie na natureza, seus aspectos evolutivos, e a relação entre conservação dos ambientes lacustres e variabilidade genética mitocondrial das populações selvagensAbstract: .RFLP (Restriction Fragment Length Polymorphism) analysis of mitochondrial DNA was carried out to investigate the population genetic structure and its potential as a tool to identify and manage the cultured and wild populations of Pirapitinga-do-sul ¿ Brycon opalinus (Cuvier, 1819) (Characiforme, Characidae, Bryconiae) in the Paraíba do sul watershed. DNA samples from 283 fish, collected in 7 rivers of Paraíba watershed and in the Hydrobiology and Aquaculture Station of Paraibuna (CESP), were analysied. 24 restriction enzymes were screened and 6 (Apa I, Ava ll, EcoR I, Hinc ll, Hpa I, Nhe I) of them which produced multiple cutling sites in the molecule were selected. The combination of the 6 informative enzymes .revealed 27 haplotypes. The mtDNA of Pirapitinga-do-sul had 16.300 ( ± 500) bp long. No length heteroplasmy was found but restriction site heteroplasmy was observed in 17.5% of the fish from the Hydrobiology and Aquaculture Station of Paraibi.ma (CESP), as well as in 2.7% of the samples from Negro River, and 15.7% from Peixe River. Two haplotypes (25 and 26) were tound exclusively in the hatchery facilities. Such haplotypes can provide information on both the survival and long term reproductive success of stocked fish. Haplotype diversities were high both in the population from the Aquaculture Station (h=0.75), and from the wild (h=0.62). Nucleotide diversity among the 27 haplotypes found for the Brycon opalinus was 0.825%. The molecular variance analysis (AMOVA - nAnalysis of MOlecular V Ariancen) showed that the largest percentage of variance was observed within populations (70,02%). However, 15,97% of the total diversity were explained by interpopulation variance. Computer simulations of mt DNA variabilty indices were used to appraise the present situation of broodstock kept in captivity for stocking purposes. Also, genetic structure of natural populations, its evolution aspects and the relationship between conservation of riverine habitats and mitochondrial genetic variability of wild populations were discussed.DoutoradoFisiologiaDoutor em Ciência