Genetic heterogeneity in natural beds of the razor clam "Ensis siliqua" revealed by microsatellites

[Abstract] The aim of this study was to analyse the genetic diversity and population structure in the razor clam Ensis siliqua along the European Atlantic coast taking into account their recent history of exploitation and the ‘Prestige' oil spill. To this end we examined the genetic variability of microsatellite markers in 211 razor clams from five populations in Ireland, Portugal and Spain. Microsatellite data revealed a low genetic differentiation between the Spanish and Portuguese populations (FST = 0–0.032) and a moderate differentiation of these populations and the Irish samples (FST = 0.071–0.100). Although we observed changes in genetic diversity in accordance with the level of exploitation and the distribution of the oil spill, these changes were mild and not significant after Bonferroni correction. This could be the result of a genuine low impact, lack of statistical power and/or the capacity of this species to recolonize quickly after the impact of anthropogenic stressors. Supporting the latter argument we found a significant temporal heterogeneity of allelic frequencies in samples coming from the same sampling locality that could be attributed to the movement of adults or larvae from unaffected source populations

Temporal genetic variation of microsatellite markers in the razor clam "Ensis arcuatus" (Bivalvia: Pharidae)

[Abstract] The aim of this study was to characterize new microsatellite loci in the razor clam Ensis arcuatus (Bivalvia: Pharidae) and examine the temporal genetic variability of a natural bed in Cies Islands (Galicia, north-western Spain) exploited by apnoea divers and affected by the ‘Prestige’ oil tanker spill in November 2002. In this work, we characterized four polymorphic microsatellites using an alternative approach that relies on the amplification and sequencing of ISSR markers. Observed heterozygosities ranged from 0.1053–0.6800 and number of alleles from 4–19. Linkage equilibrium was observed in all loci and two of them showed significant deviations from Hardy–Weinberg equilibrium. Estimators of FST between samples were low (<0.05) and not different from zero with a confidence level of 5%. We did not detect a clear decreasing tendency in genetic diversity although we found a significant change in allelic frequencies among samples (P = 0.0024) after the ‘Prestige’ oil spill. We propose that both phenomena could be related to a high variance in genetic success and/or a movement of adults or larvae from different source populations.Xunta de Galicia; PGIDT03PXIB10302PRXunta de Galicia; PGIDT03MA10301PRXunta de Galicia; IN840DXunta de Galicia; IN809

Long-term dietary folate deficiency accelerates progressive hearing loss on CBA/Ca mice

This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).Dietary folic acid deficiency induced early hearing loss in C57BL/6J mice after two-months, corroborating the epidemiological association previously described between vitamin deficiency and this sensory impairment. However, this strain is prone to early hearing loss, and hence we decided to analyze whether the effects exerted by folate deprivation follow the same pattern in a mouse strain such as CBA/Ca, which is resistant to hearing impairment. Here, we show results of a long-term study on hearing carried out on CBA/Ca mice subjected to dietary folate deprivation. Systemic changes included decreased serum folate levels, hyperhomocysteinemia and signs of anemia in the group fed the folate-deficient diet. Initial signs of hearing loss were detected in this strain after 8-months of vitamin deficiency, and correlated with histological damage in the cochleae. In conclusion, the data presented reinforce the importance of adequate folic acid levels for the auditory system and suggest that the impact of dietary deficiencies may depend on the genetic background.RM was a fellow of the JAE-CSIC predoctoral program. This work was supported by grants of the Ministerio de Economía y Competitividad (SAF2014-53979-R to IV; BFU2009-08977 to MP), the European Union (FP7-AFHELO and TARGEAR to IV).Peer reviewe

Heterogeneous nature and distribution of interruptions in dinucleotides may indicate the existence of biased substitutions underlying microsatellite evolution

[Abstract] Some aspects of microsatellite evolution, such as the role of base substitutions, are far from being fully understood. To examine the significance of base substitutions underlying the evolution of microsatellites we explored the nature and the distribution of interruptions in dinucleotide repeats from the human genome. The frequencies that we inferred in the repetitive sequences were statistically different from the frequencies observed in other noncoding sequences. Additionally, we detected that the interruptions tended to be towards the ends of the microsatellites and 5′-3′ asymmetry. In all the estimates nucleotides forming the same repetitive motif seem to be affected by different base substitution rates in AC and AG. This tendency itself could generate patterning and similarity in flanking sequences and reconcile these phenomena with the high mutation rate found in flanking sequences without invoking convergent evolution. Nevertheless, our data suggest that there is a regional bias in the substitution pattern of microsatellites. The accumulation of random substitutions alone cannot explain the heterogeneity and the asymmetry of interruptions found in this study or the relative frequency of different compound microsatellites in the human genome. Therefore, we cannot rule out the possibility of a mutational bias leading to convergent or parallel evolution in flanking sequences

Development of Microsatellite Markers in the Razor Clam Solen Marginatus (Bivalvia: Solenidae)

[Abstract] Four microsatellite loci in the razor clam Solen marginatus are described. Loci were isolated from the sequences of intersimple sequence repeat (ISSR) markers and an enriched library. Detailed analysis of these sequences led to the design of eight primer pairs. Allelic variation was assessed in 20 individuals from Redondela, Spain. The genetic variation observed in the markers presented here will be useful for future studies on the population structure of Solen marginatus in the wild and for aquaculture of this species.Xunta de Galicia; PGIDT03MA10301PR

Isolation and characterization of polymorphic microsatellite loci in the razor clam "Ensis siliqua"

[Abstract] Five polymorphic microsatellite loci in the razor clam Ensis siliqua are described. A collection consisting of 34 individuals from Finisterre, Spain, was analysed. Loci were isolated from the sequences of intersimple sequence repeat (ISSR) markers. Detailed analysis of 42 ISSR markers led to the design of 16 primer pairs. Five of these yielded consistent and polymorphic products. The number of alleles ranged from five to 23 per locus with the observed heterozygosity ranging from 0.46 to 0.94. Linkage equilibrium was observed in all loci and three of them showed significant deviations from Hardy–Weinberg equilibrium

Genetic divergence detected by ISSR markers and characterization of microsatellite regions in "Mytilus" mussels

[Abstract] The wide distribution of microsatellites in mussels of the Mytilus edulis complex (Mytilidae) enables the analysis of inter-simple-sequence repeat (ISSR) markers. The aim of this investigation was to assess genetic differentiation in six sampling localities distributed along the European Atlantic coast to expose the potential of these markers in genetic studies requiring the detection of low polymorphism and as a source of sequences for developing microsatellite markers. We detected low genetic structuring within each member of the Mytilus edulis complex. Nei and Li distances and AMOVA clustered the individuals studied into two groups. On the basis of these results two sampling localities coming from the M. edulis × M. galloprovincialis mosaic hybrid zone in Western Europe were assigned to one species. On the other hand, mussels of a sampling locality in the Baltic Sea were not significantly different from a pure M. edulis locality supporting an extensive introgression of M. edulis in these individuals. Finally, 148 microsatellites were found in the sequences of 51 ISSR markers, and two polymorphic microsatellite markers were developed.Xunta de Galicia; PGIDT10PX110304P

Reflections on an educational program on moral and civic virtues and values in secondary schools. A case study in Mexico.

The research we present is part of the project Researching and Promoting Character Education in Latin American Secondary Schools funded by the Templeton World Charity Foundation.In this research work we present a case study, focusing on the values program implemented in a Mexican public school in the central area of the country. Our exploration of the capacity of the school when implementing the values program is based on the analysis of documents provided by the school which are related with the project, semi-structured interviews, in-depth interviews, images and the participatory observation carried out in the school over a period of three weeks. The wealth of informants (principals, teachers, pupils and parents) allowed us to gather a broader variety of information on the reality of the values program applied