Habitat uncertainty explains variation in offspring provisioning strategies in a temporary pond crustacean

Along with the development of nanotechnology, an increase in production and application of nanosized magnetite (Fe₃O₄) is expected. Though magnetite is considered relatively safe, information concerning potential hazards of synthetic magnetite nanoparticles with unique physico-chemical characteristics to aquatic organisms is still limited. In this study, we evaluated the toxicity of nanosized (27.2 ± 9.8 nm) and bulk (144.2 ± 67.7 nm) magnetite particles to different life stages of the aquatic crustacean Daphnia magna. In addition, phytotoxicity of the magnetite was evaluated using duckweed Lemna minor. The study did not reveal any statistically significant differences between the biological effects of nanosized and bulk magnetite particles. Both forms of magnetite induced very low toxicity (EC50 > 100 ppm) to D. magna and L. minor in the standard acute assays. However, it was demonstrated that at acutely subtoxic magnetite concentrations (10 and 100 ppm), the number of neonates hatched from D. magna ephippia was decreased. Moreover, short-term (48 h) exposure of neonate daphnids to these concentrations may significantly affect the long-term survival and reproductive potential of daphnids. These results indicate that substantial contamination of aquatic ecosystems by magnetite may disrupt the stability of cladoceran populations.     

Arenavirus Dynamics in Experimentally and Naturally Infected Rodents

Infectious diseases of wildlife are typically studied using data on antibody and pathogen levels. In order to interpret these data, it is necessary to know the course of antibodies and pathogen levels after infection. Such data are typically collected using experimental infection studies in which host individuals are inoculated in the laboratory and sampled over an extended period, but because laboratory conditions are controlled and much less variable than natural conditions, the immune response and pathogen dynamics may differ. Here, we compared Morogoro arenavirus infection patterns between naturally and experimentally infected multimammate mice (Mastomys natalensis). Longitudinal samples were collected during three months of bi-weekly trapping in Morogoro, Tanzania, and antibody titer and viral RNA presence were determined. The time of infection was estimated from these data using a recently developed Bayesian approach, which allowed us to assess whether the natural temporal patterns match the previously observed patterns in the laboratory. A good match was found for 52% of naturally infected individuals, while most of the mismatches can be explained by the presence of chronically infected individuals (35%), maternal antibodies (10%), and an antibody detection limit (25%). These results suggest that while laboratory data are useful for interpreting field samples, there can still be differences due to conditions that were not tested in the laboratory.     

How tree species identity and diversity affect light transmittance to the understory in mature temperate forests

Light is a key resource for plant growth and is of particular importance in forest ecosystems, because of the strong vertical structure leading to successive light interception from canopy to forest floor. Tree species differ in the quantity and heterogeneity of light they transmit. We expect decreases in both the quantity and spatial heterogeneity of light transmittance in mixed stands relative to monocultures, due to complementarity effects and niche filling. We tested the degree to which tree species identity and diversity affected, via differences in tree and shrub cover, the spatiotemporal variation in light availability before, during, and after leaf expansion. Plots with different combinations of three tree species with contrasting light transmittance were selected to obtain a diversity gradient from monocultures to three species mixtures. Light transmittance to the forest floor was measured with hemispherical photography. Increased tree diversity led to increased canopy packing and decreased spatial light heterogeneity at the forest floor in all of the time periods. During leaf expansion, light transmittance did differ between the different tree species and timing of leaf expansion might thus be an important source of variation in light regimes for understory plant species. Although light transmittance at the canopy level after leaf expansion was not measured directly, it most likely differed between tree species and decreased in mixtures due to canopy packing. A complementary shrub layer led, however, to similar light levels at the forest floor in all species combinations in our plots. Synthesis. We find that a complementary shrub layer exploits the higher light availability in particular tree species combinations. Resources at the forest floor are thus ultimately determined by the combined effect of the tree and shrub layer. Mixing species led to less heterogeneity in the amount of light, reducing abiotic niche variability.     

Long‐term seed bank dynamics in a temperate forest under conversion from coppice‐with‐standards to high forest management

Questions: How do changes in forest management, i.e. in disturbance type and frequency, influence species diversity, abundance and composition of the seed bank? How does the relationship between seed bank and vegetation change? What are the implications for seed bank dynamics? Location: An ancient Quercus petraea — Carpinus betulus forest in conversion from coppice‐with‐standards to regular Quercus high forest near Montargis, France. Methods: Seed bank and vegetation were sampled in six replicated stand types, forming a chronosequence along the conversion pathway. The stand types represented mid‐successional stages of stands in transition from coppice‐with‐standards (to high forest (16 plots) and early‐ and mid‐successional high forest stands (32 plots). Results: Seed bank density and species richness decreased with time since last disturbance. Adjusting for seed density effects obscured species richness differences between stand types, but species of later seres were nested subsets of earlier seres, implying concomitant shifts in species richness and composition with time since disturbance. Later seres were characterized by species with low seed weight and high seed longevity. Seed banks of early seres were more similar to vegetation than to later seres. Conclusions: Abandonment of the coppice‐with‐standards regime altered the seed bank characteristics, as well as its relationship with vegetation. Longer management cycles under high forest yield impoverished seed banks. For their persistence, seed bank species will increasingly rely on management of permanently open areas in the forest landscape. Thus, revegetation at the beginning of new high‐forest cycles may increasingly depend on inflow from seed sources.     

Quantifying the Hydroregime of a Temporary Pool Habitat: A Modelling Approach for Ephemeral Rock Pools in SE Botswana

Ecological and evolutionary processes in temporary rock pools operate within constraints imposed by their hydrologic regimes. These shallow pools flood when seasonal rains accumulate on impermeable substrates. Despite the ecological importance of hydrologic conditions for these ecosystems, we typically lack tools and empirical data required to understand the implications of hydrologic variability and climate change for biotic populations and communities in these habitats. In this study, we developed a hydrologic model to simulate rock pool hydrologic regimes based on rainfall, evapotranspiration, and basin geometry. The model was used to investigate long-term patterns of seasonal and inter-annual variation in hydroregime. In addition, hydrologic conditions associated with potential climate change scenarios were simulated and evaluated with respect to the biological requirements of the anostracan Branchipodopsis wolfi. The model’s output for daily inundation matched with field observations with an overall accuracy of 85% and correctly estimated complete hydroperiods with an overall accuracy of 70%. Simulations indicate large variation in individual hydroperiods (76–115%) as well as in the number of hydroperiods per year (19–23%). Furthermore, this study suggests that climate change may significantly alter the rock pool hydroregime. These findings confirm the hydrologic sensitivity of these ephemeral habitats to precipitation patterns, and their potential sensitivity to future climate change. Modelling indicates that the suitability of average inundation conditions for B. wolfi deteriorates significantly under future climate predictions. High levels of spatial and temporal variation in hydrologic conditions are dominant features of these habitats and an essential consideration for understanding population and community-level ecological processes.     

Desflurane consumption during automated closed-circuit delivery is higher than when a conventional anesthesia machine is used with a simple vaporizer-O2-N2O fresh gas flow sequence

Background

Current analgesics have drawbacks such as delays in acquisition, lag-times for effect, and side effects. We recently presented a preliminary report of a new analgesic method involving a two-minute sciatic nerve press, which resulted in immediate short-term relief of pain associated with dental and renal diseases. The present study investigated whether this technique was effective for pain associated with other disease types, and whether the relief was effective for up to one hour.

Methods

This randomized, placebo-controlled, parallel-group trial was conducted in four hospitals in Anhui Province, China. Patients with pain were sequentially recruited by participating physicians during clinic visits, and 135 patients aged 15 – 80 years were enrolled. Dental disease patients included those with acute pulpitis and periapical abscesses. Renal disease patients included those with kidney infections and/or stones. Tumor patients included those with nose, breast, stomach and liver cancers, while Emergency Room patients had various pathologies. Patients were randomly assigned to receive a "sciatic nerve press" in which pressure was applied simultaneously to the sciatic nerves at the back of both thighs, or a "placebo press" in which pressure was applied to a parallel region on the front of the thighs. Each fist applied a pressure of 11 – 20 kg for 2 minutes. Patients rated their level of pain before and after the procedure.

Results

The "sciatic nerve press" produced immediate relief of pain in all patient groups. Emergency patients reported a 43.5% reduction in pain (p < 0.001). Significant pain relief for dental, renal and tumor patients lasted for 60 minutes (p < 0.001). The peak pain relief occurred at the 10 – 20^th minutes, and the relief decreased 47% by the 60^th minutes.

Conclusion

Two minutes of pressure on both sciatic nerves produced immediate significant short-term conduction analgesia. This technique is a convenient, safe and powerful method for the short-term treatment of clinical pain associated with a diverse range of pathologies.

Trial registration

Current Controlled Trials ACTRN012606000439549     

Specific immuno capturing of the Staphylococcal superantigen toxic‐shock syndrome toxin‐1 in plasma

Toxic‐shock syndrome is primarily caused by the Toxic‐shock syndrome toxin 1 (TSST‐1), which is secreted by the Gram‐positive bacterium Staphylococcus aureus. The toxin belongs to a family of superantigens (SAgs) which exhibit several shared biological properties, including the induction of massive cytokine release and V_β‐specific T‐cell proliferation. In this study we explored the possibility to use monoclonal Variable domains of Llama Heavy‐chain antibodies (VHH) in the immuno capturing of TSST‐1 from plasma. Data is presented that the selected VHHs are highly specific for TSST‐1 and can be efficiently produced in large amounts in yeast. In view of affinity chromatography, the VHHs are easily coupled to beads, and are able to deplete TSST‐1 from plasma at very low, for example, pathologically relevant, concentrations. When spiked with 4 ng/mL TSST‐1 more than 96% of TSST‐1 was depleted from pig plasma. These data pave the way to further explore application of high‐affinity columns in the specific immuno depletion of SAgs in experimental sepsis models and in sepsis in humans. Biotechnol. Bioeng. 2009; 104: 143–151 © 2009 Wiley Periodicals, Inc.     

Memory keeps you at home: a mechanistic model for home range emergence

Despite its central place in animal ecology no general mechanistic movement model with an emergent home-range pattern has yet been proposed. Random walk models, which are commonly used to model animal movement, show diffusion instead of a bounded home range and therefore require special modifications. Current approaches for mechanistic modeling of home ranges apply only to a limited set of taxa, namely territorial animals and/or central place foragers. In this paper we present a more general mechanistic movement model based on a biased correlated random walk, which shows the potential for home-range behavior. The model is based on an animal tracking a dynamic resource landscape, using a biologically plausible two-part memory system, i.e. a reference- and a working-memory. Our results show that by adding these memory processes the random walker produces home-range behavior as it gains experience, which also leads to more efficient resource use. Interestingly, home-range patterns, which we assessed based on home-range overlap and increase in area covered with time, require the combined action of both memory components to emerge. Our model has the potential to predict home-range size and can be used for comparative analysis of the mechanisms shaping home-range patterns.     

Characterization of Coastal Urban Watershed Bacterial Communities Leads to Alternative Community-Based Indicators

Background

Microbial communities in aquatic environments are spatially and temporally dynamic due to environmental fluctuations and varied external input sources. A large percentage of the urban watersheds in the United States are affected by fecal pollution, including human pathogens, thus warranting comprehensive monitoring.

Methodology/Principal Findings

Using a high-density microarray (PhyloChip), we examined water column bacterial community DNA extracted from two connecting urban watersheds, elucidating variable and stable bacterial subpopulations over a 3-day period and community composition profiles that were distinct to fecal and non-fecal sources. Two approaches were used for indication of fecal influence. The first approach utilized similarity of 503 operational taxonomic units (OTUs) common to all fecal samples analyzed in this study with the watershed samples as an index of fecal pollution. A majority of the 503 OTUs were found in the phyla Firmicutes, Proteobacteria, Bacteroidetes, and Actinobacteria. The second approach incorporated relative richness of 4 bacterial classes (Bacilli, Bacteroidetes, Clostridia and α-proteobacteria) found to have the highest variance in fecal and non-fecal samples. The ratio of these 4 classes (BBC∶A) from the watershed samples demonstrated a trend where bacterial communities from gut and sewage sources had higher ratios than from sources not impacted by fecal material. This trend was also observed in the 124 bacterial communities from previously published and unpublished sequencing or PhyloChip- analyzed studies.

Conclusions/Significance

This study provided a detailed characterization of bacterial community variability during dry weather across a 3-day period in two urban watersheds. The comparative analysis of watershed community composition resulted in alternative community-based indicators that could be useful for assessing ecosystem health.