Spatial ecology and habitat use of two-spined blackfish Gadopsis bispinosus in an upland reservoir

The scale and patterns of movement and habitat use are primary considerations in the conservation and management of threatened species. Movement, activity and habitat use of the threatened two-spined blackfish Gadopsis bispinosus were assessed in a small upland reservoir in south-eastern Australia using manual and remote radio-telemetry. Movements and activity of two-spined blackfish (n?=?19) were studied over a 28-day period and exhibited proportionately large directional crepuscular movement and activity with heightened activity continuing throughout the night (although movement was subdued). Two daily movement strategies were observed: movements from diurnal home-shelter habitats (predominantly rock) to macrophytes at night (14 individuals), and occupation of macrophytes during the entire diel period and restricted movement (five individuals). Daily movement strategies were fixed (not plastic) among all individuals, with one exception, for the duration of the study period. Rock, fallen timber and macrophytes were the most commonly used daytime shelter habitat (in order of preference). Although some information exists on movements and habitat use of this species and the congeneric river blackfish G. Marmoratus in lotic environments, we present the first study of movements and habitat use for either species in lentic environments. Given the occupation of lentic environments by this threatened species, the data presented in this study provide insight into the habitat requirements for this species, and offer opportunities for habitat enhancement in existing reservoirs within the species’ geographic range.     

Vulnerability to xylem cavitation of Hakea species (Proteaceae) from a range of biomes and life histories predicted by climatic niche

Background and AimsExtreme drought conditions across the globe are impacting biodiversity, with serious implications for the persistence of native species. However, quantitative data on physiological tolerance are not available for diverse flora to inform conservation management. We quantified physiological resistance to cavitation in the diverse Hakea genus (Proteaceae) to test predictions based on climatic origin, life history and functional traits.MethodsWe sampled terminal branches of replicate plants of 16 species in a common garden. Xylem cavitation was induced in branches under varying water potentials (tension) in a centrifuge, and the tension generating 50 % loss of conductivity (stem P₅₀) was characterized as a metric for cavitation resistance. The same branches were used to estimate plant functional traits, including wood density, specific leaf area and Huber value (sap flow area to leaf area ratio).Key ResultsThere was significant variation in stem P₅₀ among species, which was negatively associated with the species climate origin (rainfall and aridity). Cavitation resistance did not differ among life histories; however, a drought avoidance strategy with terete leaf form and greater Huber value may be important for species to colonize and persist in the arid biome.ConclusionsThis study highlights climate (rainfall and aridity), rather than life history and functional traits, as the key predictor of variation in cavitation resistance (stem P₅₀). Rainfall for species origin was the best predictor of cavitation resistance, explaining variation in stem P₅₀, which appears to be a major determinant of species distribution. This study also indicates that stem P₅₀ is an adaptive trait, genetically determined, and hence reliable and robust for predicting species vulnerability to climate change. Our findings will contribute to future prediction of species vulnerability to drought and adaptive management under climate change.     

Reversal potentials corresponding to mechanical stimulation and leakage current in Myxicola giant axons

The response of a Myxicola infundibulum giant axon to a transverse mechanical stimulus is an increase in membrane conductance. The similarity of the reversal potential for this conductance increase and the reversal potential for leakage current, together with other similarities, suggest similar pathways for these two processes. Depolarization of the reversal potential with increased mechanical stimulus is best explained in terms of a gradual change in the mechanically-stimulated ionic pathways.     

Xylem traits mediate a trade-off between resistance to freeze-thaw-induced embolism and photosynthetic capacity in overwintering evergreens

Hydraulic traits were studied in temperate, woody evergreens in a high-elevation heath community to test for trade-offs between the delivery of water to canopies at rates sufficient to sustain photosynthesis and protection against disruption to vascular transport caused by freeze-thaw-induced embolism. Freeze-thaw-induced loss in hydraulic conductivity was studied in relation to xylem anatomy, leaf- and sapwood-specific hydraulic conductivity and gas exchange characteristics of leaves. We found evidence that a trade-off between xylem transport capacity and safety from freeze-thaw-induced embolism affects photosynthetic activity in overwintering evergreens. The mean hydraulically weighted xylem vessel diameter and sapwood-specific conductivity correlated with susceptibility to freeze-thaw-induced embolism. There was also a strong correlation of hydraulic supply and demand across species; interspecific differences in stomatal conductance and CO(2) assimilation rates were correlated linearly with sapwood- and leaf-specific hydraulic conductivity. Xylem vessel anatomy mediated an apparent trade-off between resistance to freeze-thaw-induced embolism and hydraulic and photosynthetic capacity during the winter. These results point to a new role for xylem functional traits in determining the degree to which species can maintain photosynthetic carbon gain despite freezing events and cold winter temperatures.     

Genetic association analysis highlights new loci that modulate hematological trait variation in Caucasians and African Americans

Red blood cell, white blood cell, and platelet measures, including their count, sub-type and volume, are important diagnostic and prognostic clinical parameters for several human diseases. To identify novel loci associated with hematological traits, and compare the architecture of these phenotypes between ethnic groups, the CARe Project genotyped 49,094 single nucleotide polymorphisms (SNPs) that capture variation in ~2,100 candidate genes in DNA of 23,439 Caucasians and 7,112 African Americans from five population-based cohorts. We found strong novel associations between erythrocyte phenotypes and the glucose-6 phosphate dehydrogenase (G6PD) A-allele in African Americans (rs1050828, P<2.0×10(-13), T-allele associated with lower red blood cell count, hemoglobin, and hematocrit, and higher mean corpuscular volume), and between platelet count and a SNP at the tropomyosin-4 (TPM4) locus (rs8109288, P=3.0×10(-7) in Caucasians; P=3.0×10(-7) in African Americans, T-allele associated with lower platelet count). We strongly replicated many genetic associations to blood cell phenotypes previously established in Caucasians. A common variant of the α-globin (HBA2-HBA1) locus was associated with red blood cell traits in African Americans, but not in Caucasians (rs1211375, P<7×10(-8), A-allele associated with lower hemoglobin, mean corpuscular hemoglobin, and mean corpuscular volume). Our results show similarities but also differences in the genetic regulation of hematological traits in European- and African-derived populations, and highlight the role of natural selection in shaping these differences.     

Identification of legume RopGEF gene families and characterization of a Medicago truncatula RopGEF mediating polar growth of root hairs

Root hairs play important roles in the interaction of plants with their environment. Root hairs anchor the plant in the soil, facilitate nutrient uptake from the rhizosphere, and participate in symbiotic plant-microbe interactions. These specialized cells grow in a polar fashion which gives rise to their elongated shape, a process mediated in part by a family of small GTPases known as Rops. RopGEFs (GEF, guanine nucleotide exchange factor) activate Rops to effect tip growth in Arabidopsis pollen and root hairs, but the genes mediating tip growth in legumes have not yet been characterized. In this report we describe the Rop and RopGEF gene families from the model legume Medicago truncatula and from the crop legume soybean. We find that one member of the M. truncatula gene family, MtRopGEF2, is required for root hair development because silencing this gene by RNA interference affects the cytosolic Ca2+ gradient and subcellular structure of root hairs, and reduces root hair growth. Consistent with its role in polar growth, we find that a GFP::MtRopGEF2 fusion protein localizes in the apex of emerging and actively growing root hairs. The amino terminus of MtRopGEF2 regulates its ability to interact with MtRops in yeast, and regulates its biological activity in vivo.     

Experimental evidence that women's mate preferences are directly influenced by cues of pathogen prevalence and resource scarcity

When choosing a mate, women are thought to face a trade-off between genetic and parental quality. Recent research suggests that this trade-off is influenced by environmental factors such as pathogen prevalence and resource scarcity, which affect the relative value of genetic and parental quality to offspring fitness. To further investigate these findings, the current study primed 60 women with pathogen prevalence, resource scarcity or an irrelevant threat, before administering a forced trade-off task that assessed mate preferences for traits thought to be indicative of genetic or parental quality. Women primed with pathogen prevalence revealed greater preferences for traits indicative of genetic quality at the expense of traits indicative of parental quality. The reverse was found for women primed with resource scarcity. These findings suggest that environmental factors may directly influence women's mate preferences owing to evolved plasticity, such that mate preferences are flexible in response to environmental factors.     

Performance of predictive models in marine benthic environments based on predictions of sponge distribution on the Australian continental shelf

This study tested the performance of 15 predictive models in predicting the distribution of sponge assemblages on the Australian continental shelf using a common set of marine environmental variables. The models included traditional regression and more recently developed machine learning models. The results demonstrate that the spatial distribution of sponge assemblages can be successfully predicted, although the effectiveness of predictions varied among models. Overall, machine learning models achieved the best prediction performance. The direct variable of bottom-water temperature and the resource variables that describe bottom-water nutrient status were found to be useful surrogates for the distribution of sponge assemblages at the broad regional scale. A new method of deriving pseudo-absence data (weighted pseudo-absence) was compared with random pseudo-absence data — the new data were able to improve modelling performance for all the models both in terms of statistics (~ 10%) and in the predicted spatial distributions. Results from this study will further refine modelling methods used to predict the spatial distribution of marine biota at broad spatial scales, an outcome especially relevant to managers of marine resources.     

2-D DIGE analysis of the mitochondrial proteome from human skeletal muscle reveals time course-dependent remodelling in response to 14 consecutive days of endurance exercise training

Adaptation of skeletal muscle to repeated bouts of endurance exercise increases aerobic capacity and improves mitochondrial function. However, the adaptation of human skeletal muscle mitochondrial proteome to short‐term endurance exercise training has not been investigated. Eight sedentary males cycled for 60 min at 80% of peak oxygen consumption (VO_2peak) each day for 14 consecutive days, resulting in an increase in VO_2peak of 17.5±3.8% (p<0.01). Mitochondria‐enriched protein fractions from skeletal muscle biopsies taken from m. vastus lateralis at baseline, and on the morning following the 7th and 14th training sessions were subjected to 2‐D DIGE analysis with subsequent MS followed by database interrogation to identify the proteins of interest. Thirty‐one protein spots were differentially expressed after either 7 or 14 days of training (ANOVA, p<0.05). These proteins included subunits of the electron transport chain, enzymes of the tricarboxylic acid cycle, phosphotransfer enzymes, and regulatory factors in mitochondrial protein synthesis, oxygen transport, and antioxidant capacity. Several proteins demonstrated a time course‐dependent induction during training. Our results illustrate the phenomenon of skeletal muscle plasticity with the extensive remodelling of the mitochondrial proteome occurring after just 7 days of exercise training suggestive of enhanced capacity for adenosine triphosphate generation at a cellular level.     

Quantifying the importance of MSP1-19 as a target of growth-inhibitory and protective antibodies against Plasmodium falciparum in humans

Background

Antibodies targeting blood stage antigens are important in protection against malaria, but the key targets and mechanisms of immunity are not well understood. Merozoite surface protein 1 (MSP1) is an abundant and essential protein. The C-terminal 19 kDa region (MSP1-19) is regarded as a promising vaccine candidate and may also be an important target of immunity.

Methodology/Findings

Growth inhibitory antibodies against asexual-stage parasites and IgG to recombinant MSP1-19 were measured in plasma samples from a longitudinal cohort of 206 children in Papua New Guinea. Differential inhibition by samples of mutant P. falciparum lines that expressed either the P. falciparum or P. chabaudi form of MSP1-19 were used to quantify MSP1-19 specific growth-inhibitory antibodies. The great majority of children had detectable IgG to MSP1-19, and high levels of IgG were significantly associated with a reduced risk of symptomatic P. falciparum malaria during the 6-month follow-up period. However, there was little evidence of PfMSP1-19 specific growth inhibition by plasma samples from children. Similar results were found when testing non-dialysed or dialysed plasma, or purified antibodies, or when measuring growth inhibition in flow cytometry or microscopy-based assays. Rabbit antisera generated by immunization with recombinant MSP1-19 demonstrated strong MSP1-19 specific growth-inhibitory activity, which appeared to be due to much higher antibody levels than human samples; antibody avidity was similar between rabbit antisera and human plasma.

Conclusions/Significance

These data suggest that MSP1-19 is not a major target of growth inhibitory antibodies and that the protective effects of antibodies to MSP1-19 are not due to growth inhibitory activity, but may instead be mediated by other mechanisms. Alternatively, antibodies to MSP1-19 may act as a marker of protective immunity.