Abstract: We pursue the study of S Arae, an RRab Lyrae Blazho star, using unique, uninterrupted and accurate optical photometric data acquired from Antarctica at Dome C by PAIX – Photometer AntarctIca eXtraction – during 150 d. The PAIX data were analysed using both Period04 and PDM13. Besides a main pulsation period of 0.452 d and a modulation period of 47.264 d, three other significant frequencies were found. Multiplet patterns, up to the ninth order, were also extracted, showing a clear asymmetric structure. Following these results, a new approximation of the main-frequency harmonics amplitude decrease is suggested, replacing the usual exponential fit by a hyperbolic one. The physical properties of the Blazhko star, namely metallicity, temperature, mass, were obtained using a new approach based on the study of these parameters for each Blazhko phase. Finally, the PAIX data reveal a residual scatter that occurs during a small phase interval, 10 per cent of the pulsation period, corresponding to the phase of the main shock passage across the atmosphere. The position of the so-called main bump, corresponding to the shock resulting from the infalling atmosphere and the expanding photosphere, varies from one cycle to another and, moreover, around this main bump, two other bumps appear and vanish at different phases during a Blazhko cycle. Following these observations, we discuss the relation between the bump topology and the Blazhko period and give new insights for future Blazhko theoretical investigations.

Abstract: The genus Borrelia consists of evolutionarily and genetically diverse bacterial species that cause a variety of diseases in humans and domestic animals. These vector-borne spirochetes can be classified into two major evolutionary groups, the Lyme borreliosis clade and the relapsing fever clade, both of which have complex transmission cycles during which they interact with multiple host species and arthropod vectors. Molecular, ecological, and evolutionary studies have each provided significant contributions towards our understanding of the natural history, biology and evolutionary genetics of Borrelia species; however, integration of these studies is required to identify the evolutionary causes and consequences of the genetic variation within and among Borrelia species. For example, molecular and genetic studies have identified the adaptations that maximize fitness components throughout the Borrelia lifecycle and enhance transmission efficacy but provide limited insights into the evolutionary pressures that have produced them. Ecological studies can identify interactions between Borrelia species and the vertebrate hosts and arthropod vectors they encounter and the resulting impact on the geographic distribution and abundance of spirochetes but not the genetic or molecular basis underlying these interactions. In this review we discuss recent findings on the evolutionary genetics from both of the evolutionarily distinct clades of Borrelia species. We focus on connecting molecular interactions to the ecological processes that have driven the evolution and diversification of Borrelia species in order to understand the current distribution of genetic and molecular variation within and between Borrelia species.

Abstract: Understanding the diving behaviour of diving predators in relation to concomitant prey distribution could have major practical applications in conservation biology by allowing the assessment of how changes in fine scale prey distribution impact foraging efficiency and ultimately population dynamics. The southern elephant seal (Mirounga leonina, hereafter SES), the largest phocid, is a major predator of the southern ocean feeding on myctophids and cephalopods. Because of its large size it can carry bio-loggers with minimal disturbance. Moreover, it has great diving abilities and a wide foraging habitat. Thus, the SES is a well suited model species to study predator diving behaviour and the distribution of ecologically important prey species in the Southern Ocean. In this study, we examined how SESs adjust their diving behaviour and horizontal movements in response to fine scale prey encounter densities using high resolution accelerometers, magnetometers, pressure sensors and GPS loggers. When high prey encounter rates were encountered, animals responded by (1) diving and returning to the surface with steeper angles, reducing the duration of transit dive phases (thus improving dive efficiency), and (2) exhibiting more horizontally and vertically sinuous bottom phases. In these cases, the distance travelled horizontally at the surface was reduced. This behaviour is likely to counteract horizontal displacement from water currents, as they try to remain within favourable prey patches. The prey encounter rate at the bottom of dives decreased with increasing diving depth, suggesting a combined effect of decreased accessibility and prey density with increasing depth. Prey encounter rate also decreased when the bottom phases of dives were spread across larger vertical extents of the water column. This result suggests that the vertical aggregation of prey can regulate prey density, and as a consequence impact the foraging success of SESs. To our knowledge, this is one of only a handful of studies showing how the vertical distributions and structure of prey fields influence the prey encounter rates of a diving predator.