Inulin uptake and washout in contracting and quiescent rat papillary muscle

Equilibration and washout curves of inulin were determined in isolated rat papillary muscles. Inulin uptake did not reach a steady-state value even after a long equilibration time. The effects of contractile activity were investigated. Isometric contractions increased the rate of inulin uptake and washout. In isotonic conditions, a smaller increase in the uptake and washout was observed. These changes could be attributed to an actual increase of inulin distribution space and/or to an accelerated diffusion kinetics.     

King penguin demography since the last glaciation inferred from genome-wide data

How natural climate cycles, such as past glacial/interglacial patterns, have shaped species distributions at the high-latitude regions of the Southern Hemisphere is still largely unclear. Here, we show how the post-glacial warming following the Last Glacial Maximum (ca 18 000 years ago), allowed the (re)colonization of the fragmented sub-Antarctic habitat by an upper-level marine predator, the king penguin Aptenodytes patagonicus. Using restriction site-associated DNA sequencing and standard mitochondrial data, we tested the behaviour of subsets of anonymous nuclear loci in inferring past demography through coalescent-based and allele frequency spectrum analyses. Our results show that the king penguin population breeding on Crozet archipelago steeply increased in size, closely following the Holocene warming recorded in the Epica Dome C ice core. The following population growth can be explained by a threshold model in which the ecological requirements of this species (year-round ice-free habitat for breeding and access to a major source of food such as the Antarctic Polar Front) were met on Crozet soon after the Pleistocene/Holocene climatic transition.     

Morphofunctional research on the effects of steroid-stimulating and -inhibiting drugs on the major salivary glands of rats

Adult male albino rats underwent chronic treatment with synthetic adrenocorticotropin and Dexamethasone, and were examined for a long time after the administration of these drugs. The major salivary glands were observed by means of histological and histochemical methods. We did not find enzymatic modifications whereas morphological damage was particularly evident in the submaxillary and parotid glands, especially all after Dexamethasone treatment; this damage is to be found up to at least 14 days after the end of treatment.     

A diffusion model for population growth in random environment

The growth of a population in a randomly varying environment is modeled by replacing the Malthusian growth rate with a delta-correlated normal process. The population size is then shown to be a random process, lognormally distributed, obeying a diffusion equation of the Fokker-Planck type. The first passage time p.d.f. through any arbitrarily assigned value and the probability of absorption are derived. The asymptotic behavior of the population size is investigated.     

Modelling the distribution and compositional variation of plant communities at the continental scale

Aim

We investigate whether (1) environmental predictors allow to delineate the distribution of discrete community types at the continental scale and (2) how data completeness influences model generalization in relation to the compositional variation of the modelled entities.

Location

Europe.

Methods

We used comprehensive datasets of two community types of conservation concern in Europe: acidophilous beech forests and base‐rich fens. We computed community distribution models (CDMs) calibrated with environmental predictors to predict the occurrence of both community types, evaluating geographical transferability, interpolation and extrapolation under different scenarios of sampling bias. We used generalized dissimilarity modelling (GDM) to assess the role of geographical and environmental drivers in compositional variation within the predicted distributions.

Results

For the two community types, CDMs computed for the whole study area provided good performance when evaluated by random cross‐validation and external validation. Geographical transferability provided lower but relatively good performance, while model extrapolation performed poorly when compared with interpolation. Generalized dissimilarity modelling showed a predominant effect of geographical distance on compositional variation, complemented with the environmental predictors that also influenced habitat suitability.

Main conclusions

Correlative approaches typically used for modelling the distribution of individual species are also useful for delineating the potential area of occupancy of community types at the continental scale, when using consistent definitions of the modelled entity and high data completeness. The combination of CDMs with GDM further improves the understanding of diversity patterns of plant communities, providing spatially explicit information for mapping vegetation diversity and related habitat types at large scales.

     

Structural and physiological responses of <Emphasis Type="Italic">Halodule wrightii</Emphasis> to ocean acidification

Coastal areas face high variability of seawater pH. Ocean acidification (OA) and local stressors are enhancing this variability, which poses a threat to marine life. However, these organisms present potential phenotypic plasticity that can offer physiological and structural tools to survive in these extreme conditions. In this study, we evaluated the effects of elevated CO₂ levels and consequent pH reduction on the physiology, anatomy and ultrastructure of the seagrass Halodule wrightii. A mesocosm study was conducted in an open system during a 30-day experiment, where different concentrations of CO₂ were simulated following the natural variability observed in coastal reef systems. This resulted in four experimental conditions simulating the (i) environmental pH (control condition, without CO₂ addition) and (ii) reduced pH by ? 0.3 units, (iii) ? 0.6 units and (iv) ? 0.9 units, in relation to the field condition. The evaluated population only suffered reduced optimum quantum yield (Y(II)), leaf width and cross-section area under the lowest CO₂ addition (? 0.3 pH units) after 30 days of experiment. This fitness commitment should be related to carbon concentration mechanisms present in the evaluated species. For the highest CO₂ level, H. wrightii demonstrated a capacity to compensate any negative effect of the lowest pH. Our results suggest that the physiological behaviour of this primary producer is driven by the interactions among OA and environmental factors, like irradiance and nutrient availability. The observed behaviour highlights that high-frequency pH variability and multifactorial approaches should be applied, and when investigating the impact of OA, factors like irradiance, nutrient availability and temperature must be considered as well.     

Global distribution and status of introduced Siberian chipmunks Eutamias sibiricus

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