Genetic diversity and population structure of the sea lamprey (Petromyzon marinus L.) across its distributional range

Lampreys are a group of ancient vertebrates with 360 million years of existence. Throughout their evolution, they have acquired local adaptations to the colonized habitats, showing high plasticity and adaptive capacities. The sea lamprey (Petromyzon marinus L.) is a parasitic and anadromous species that occurs in both sides of the North Atlantic. The aims of this study were to analyse, using microsatellite markers, the genetic diversity and population structure of sea lamprey throughout its distributional range. Analyses demonstrated consistent signs of high population differentiation between European and North American samples (two-groups structure), most probably due to isolation by distance, but low differentiation among populations from the same coast. The apparent lack of homing in this species is in line with its high evolutive success, as homing may bring adults back to natal habitats that have changed, or that are intermittently unfavourable. Analyses also demonstrated higher levels of genetic diversity in North American samples; DIVERSIDADE GENÉTICA E ESTRUTURA POPULACIONAL DA LAMPREIA-MARINHA (PETROMYZON MARINUS L.) AO LONGO DA SUA ÁREA DE DISTRIBUIÇÃO Resumo: As lampreias são organismos ancestrais com cerca de 360 milhões de anos de existência. No decorrer da longa escala evolutiva têm vindo a adquirir adaptações aos locais que colonizaram, tendo uma forte capacidade evolutiva e adaptativa. A lampreia-marinha (Petromyzon marinus L.) é uma espécie parasita e anádroma que ocorre em ambas as costas do Atlântico Norte. Este estudo teve como principal objetivo estudar a diversidade genética e a estrutura populacional desta espécie ao longo da sua área de distribuição, através do uso de microssatélites. Os resultados demonstraram forte divergência entre populações das costas Este e Oeste do Atlântico Norte, provavelmente devido à elevada distância entre populações, mas pouca diferenciação entre populações da mesma costa. A ausência de homing nesta espécie terá contribuído para o seu sucesso evolutivo, uma vez que o homing pode levar indivíduos a reproduzirem-se em habitats que se tornaram desfavoráveis ou intermitentemente inapropriados. Os resultados demonstraram também uma maior variabilidade genética nas populações americanas.

Covariant Spectator Theory and Hadron Structure

We present the first results of a study on meson spectroscopy using a covariant formalism based on the Covariant Spectator Theory. Our approach is derived directly in Minkowski space and it approximates the Bethe–Salpeter equation by taking effectively into account the contributions from both ladder and crossed ladder diagrams in the $q\bar{q}$ interaction kernel. A general Lorentz structure of the kernel is tested and chiral constraints on the kernel are discussed. Results for the pion form factor are also presented.

Chiral-symmetry Breaking and Pion Structure in the Covariant Spectator Theory

We introduce a covariant approach in Minkowski space for the description of quarks and mesons that exhibits both chiral-symmetry breaking and confinement. In a simple model for the interquark interaction, the quark mass function is obtained and used in the calculation of the pion form factor. We study the effects of the mass function and the different quark pole contributions on the pion form factor.

Test of Emotion Comprehension: Exploring the underlying structure through Confirmatory Factor Analysis and Similarity Structure Analysis

Some decades of research on emotional development have underlined the contribution of several domains to emotional understanding in childhood. Based on this research, Pons and colleagues (Pons & Harris, 2002; Pons, Harris & Rosnay, 2004) have proposed the Test of Emotion Comprehension (TEC) which assesses nine domains of emotional understanding, namely the recognition of emotions, based on facial expressions; the comprehension of external emotional causes; impact of desire on emotions; emotions based on beliefs; memory influence on emotions; possibility of emotional regulation; possibility of hiding an emotional state; having mixed emotions; contribution of morality to emotional experiences. This instrument was administered individually to 182 Portuguese children aged between 8 and 11 years, of 3rd and 4th grades, in public schools. Additionally, we used the Socially in Action-Peers (SAp) (Rocha, Candeias & Lopes da Silva, 2012) to assess TEC’s criterion-related validity. Mean differences results in TEC by gender and by socio-economic status (SES) were analyzed. The results of the TEC’s psychometric analysis were performed in terms of items’ sensitivity and reliability (stability, test-retest). Finally, in order to explore the theoretical structure underlying TEC a Confirmatory Factor Analysis and a Similarity Structure Analysis were computed. Implications of these findings for emotional understanding assessment and intervention in childhood are discussed.