Marlise Ladvocat Bartholomei-Santos

High genetic differentiation of Aegla longirostri (Crustacea, Decapoda, Anomura) populations in southern Brazil revealed by multi-loci microsatellite analysis.

Species with a broad distribution rarely have the same genetic make-up throughout their entire range. In some cases, they may constitute a cryptic complex consisting of a few species, each with a narrow distribution, instead of a single-, widely distributed species. These differences can have profound impacts for biodiversity conservation planning. The genetic differentiation of four populations of Aegla longirostri, a freshwater crab found in two geographically isolated basins in Rio Grande do Sul State, Brazil, was investigated by analyzing pentanucleotide multi-loci microsatellites in a heteroduplex assay. Although no morphological differences were evident, we found significant genetic differentiation among the four populations, based on F(ST) values and clustering analysis. This high level of differentiation may be indicative of cryptic species in these populations. If this hypothesis is correct, then the species occurring in the Ibicuí-Mirim River, at the southern limit of the Atlantic Rain Forest, would be under threat, considering its very restricted distribution.

PCR-mediated recombination in development of microsatellite markers: Mechanism and implications

Protocols for microsatellite-enrichment libraries have been widely applied to several species in order to supply the most informative molecular markers for population and inbreeding studies. One drawback of these protocols is the ratio of designed primer pairs that fail to amplify the expected fragment, even after exhaustive optimization attempts. A possible cause of unsuccessful microsatellite primers may be that such loci are artifacts resulting from chimeric PCR products, instead of real genomic sequences. The microsatellite-enriched library constructed for Aegla longirostri (Crustacea, Decapoda, Anomura) showed that 29% of sequenced clones were chimeric products because these sequences shared one of the flanking regions around the same repeat motif but not the other. PCR-mediated recombination is a well-known event described for several procedures in which related sequences are used as a template. We have associated this phenomenon with microsatellite marker development. This study explained the high ratio of recombinant sequences generated in the A. longirostri microsatellite-enriched library. We discuss the mechanism and implications of PCR chimeric-product formation during microsatellite isolation.

Comparison of different methodologies for DNA extraction from Aegla longirostri

Marcadores moleculares sao ferramentas uteis para esclarecer duvidas a respeito dos Aeglidae, unico grupo de crustaceos Anomura de agua doce. Essas tecnicas dependem da obtencao de DNA de boa qualidade e sem contaminantes. O objetivo deste estudo foi comparar algumas metodologias de extracao de DNA de Aegla longirostri. Quatorze protocolos foram analisados, baseados na metodologia tradicional de extracao de DNA com fenol-cloroformio, exceto o protocolo K no qual se utilizou um Kit. Os procedimentos diferiram quanto aos tecidos utilizados e a adicao de b-mercaptoetanol ao tampao de lise. Avaliaram-se tambem diferentes tempos e maneiras de conservacao. Individuos congelados apresentaram maior degradacao do material obtido conforme o tempo em que ficaram congelados. Para os individuos conservados em alcool, aqueles mantidos em etanol 95% forneceram material de melhor qualidade. A utilizacao do Mini Kit resultou em uma quantidade muito pequena de DNA de alto peso molecular. O melhor protocolo para extracao de DNA de Aeglidae utilizou musculos e brânquias, de individuos frescos com adicao de b-mercaptoetanol ao tampao de lise.

Estimulando o “Pensamento em Árvore” em Alunos de Ensino Médio: Potencial de Contribuição dos Livros Didáticos de Biologia

This study evaluates whether biology textbooks contribute to the inclusion of an evolutionary approach to the teaching of biodiversity, with the potential to assist in the development of the “tree thinking” by the students, based on the phylogenetic systematics. All the six books available in the library of a public school in Santa Maria, RS, Brazil, were analyzed. Data were collected by analyzing the content of books, through the method of Pigel. All the books brought up the phylogenetic systematics as a mechanism of biological classification in order to stimulate a nonlinear thinking on the emergence of species and contributing to the teaching of how to build phylogenetic trees according to recent research in the area, making the textbook a facilitator of the teaching/learning process in an evolutionary perspective.