Pseudoplatystoma corruscans (Spix and Agassiz, 1829) and Pseudoplatystoma reticulatum (Eingenmann and Eigenmann, 1889) are large migratory catfishes of high biological importance and great commercial value in South America. Because fertile crossbreeds can be artificially produced in hatcheries, a high genetic proximity between these two Pimelodidae species is conceivable. Possible escape of crossbred specimens from pisciculture stations is a serious environmental concern. Despite their importance, knowledge of P. corruscans and P. reticulatum biology, ecology, population diversity and genetics is limited. In the present work, the genetic divergence between P. corruscans and P. reticulatum populations from the Paraná River Basin was analyzed on the basis of polymorphisms in ISSR fragments and in the hypervariable sequence of the mitochondrial DNA (mtDNA) control region. Estimates of intraspecific haplotype (h > 0.5) and nucleotide diversities (π < 0.01) indicate that P. corruscans and P. reticulatum have survived a historical population decline, followed by a demographic expansion. The interspecific polymorphisms within the mtDNA control region and ISSR fragments were suitable as diagnostic molecular markers and could be used to discriminate the two species. A unique Pseudoplatystoma specimen, captured in the Upper Paraná River Floodplain, was identified by these DNA diagnostic markers as a hybrid P. reticulatum × P. corruscans, which possibly escaped from pisciculture. The integrity of the natural population of P. corruscans in the Upper Paraná River is at risk of genetic introgression or homogenization due to the presence of hybrids and the transposition of P. reticulatum upstream through the Canal da Piracema at Itaipu Dam. Data presented herein improve the understanding of the genetic relatedness between P. corruscans and P. reticulatum and represent potential tools for future programs of conservation and surveillance of genetic introgression events and the genetic integrity of these populations. isolated fish populations, and this is especially threatening to the dispersion of species that undergo long-distance reproduction migrations, such as P. corruscans. Therefore, monitoring of populations is becoming essential for preserving both Pseudoplatystoma species. Molecular markers are fundamental for monitoring population genetic variability and for the surveillance of populations that are potentially at risk of losing their genetic integrity. In addition, they represent an important tool for studies of the genetic diversity and evolution of fishes. The availability of nuclear and mitochondrial DNA markers that are easily accessible and suitable for characterizing and discriminating P. corruscans and P. reticulatum is a fundamental requirement in the study and supervision of these populations. Moreover, these molecular markers could enable a better understanding of the genetic relatedness of these two species.ISSR (Inter Simple Sequence Repeats) fingerprinting is a feasible molecular tool that does ...

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The greatest diversity of anurans in the world is in Brazil and one of the major challenges is to reconcile the accelerated economic development with strategies that aim to maintain this diversity in forest fragments, often representing ESUs of some biomes. This study aimed to obtain data that will support conservation projects through the pioneering use of ISSR analysis in Neotropical anurans, estimating the intra-and interpopulation genetic diversity of four populations of P. cuvieri (Paraná and São Paulo regions). Of the 65 loci scored 58 were polymorphic, with 0.797 intrapopulation variation and 0.203 interpopulation variation. The index of interpopulation genetic diff erentiation (F ST ) proved to be high among the population of Marmeleiro-PR and the three populations of SP (F ST > 0.288); genetic dissimilarity was related to the geographical distance. The ISSR proved to be effi cient and useful molecular markers in comparison with other markers most widely used for preliminary diagnosis of genetic diversity in populations of amphibians, and could be applied as a tool for future conservation projects, since they could identify potential ESUs and infl uence decisions on the preservation of fragments.