Haemonchus contortus: development of a two-step, differential-display PCR to detect differential gene expression in nematodes from immune and naïve sheep

Haemonchus contortus is a blood-feeding nematode which parasitizes the abomasum of sheep and represents a serious constraint to sheep production. Anthelmintics are currently the most common method of worm control but the worldwide development of multiple-drug resistance and issues of residues in the food chain make alternatives to anthelmintics a priority. Biotechnology-driven solutions to parasitism include vaccines and silencing of genes regulating nematode development. To pursue gene targets that may be suitable for parasite control, a two stage differential-display PCR (dd-PCR) approach was developed to observe differential gene expression between Haemonchus from immune and control sheep. Twenty-four reproducible differentially-expressed bands were identified in 60 pairs of dd-PCR comparisons. The first of these cloned and sequenced corresponded to the H. contortus 60S ribosomal protein L35A. The remaining bands are being cloned and validated and may provide new targets for parasite control.     

Is the body the self? Women and body image

This paper discusses how women's body image or experience of the body influences their identity and self-image. What are the implications of this tendency to equate the body and the self? For many women, being a dieter represents not only something that they do, but also an important aspect of how they see themselves. We propose that choosing to become a chronic dieter is a means of regulating not just one's feelings, but also one's identity and self-image when those central aspects of the self feel threatened. Weight-loss dieting is often unsuccessful, however, and repeated dieting attempts may increase weight as often as they reduce it, so using body shape to determine self-worth or identity is a maladaptive strategy for most women.     

Is cell-mediated immunity related to the evolution of life-history strategies in birds?

According to life-history theory, the development of immune function should be balanced through evolutionary optimization of the allocation of resources to reproduction and through mechanisms that promote survival. We investigated interspecific variability in cell-mediated immune response (CMI), as measured by the phytohaemagglutinin (PHA) assay, in relation to clutch size, longevity and other life-history traits in 50 species of birds. CMI exhibited significant repeatability within species, and PHA responses in chicks were consistently stronger than in adults. Univariate tests showed a variety of significant relationships between the CMI of both chicks and adults with respect to size, development period and lifespan, but not clutch size or prevalence of blood parasites in adults. Multivariate analyses confirmed these patterns but independent variables were too highly correlated to isolate unique influences on CMI. The positive relationship of chick CMI to nestling period is further complicated by a parallel relationship of chick CMI to the age at testing. However, multivariate analysis showed that chick CMI varies uniquely with length of the nestling period. Adult CMI was associated with a strong life-history axis of body size, development rate and longevity. Therefore, adult CMI may be associated with prevention and repair mechanisms related to long lifespan, but it also may be allometrically related to body size through other pathways. Neither chick CMI nor adult CMI was related to clutch size, contradicting previous results linking parasite-related mortality to CMI and the evolution of clutch size (reproductive investment) in birds.     

Is phylogenetic relatedness to native species important for the establishment of reptiles introduced to California and Florida?

Aim Charles Darwin posited that introduced species with close relatives were less likely to succeed because of fiercer competition resulting from their similarity to residents. There is much debate about the generality of this rule, and recent studies on plant and fish introductions have been inconclusive. Information on phylogenetic relatedness is potentially valuable for explaining invasion outcomes and could form part of screening protocols for minimizing future invasions. We provide the first test of this hypothesis for terrestrial vertebrates using two new molecular phylogenies for native and introduced reptiles for two regions with the best data on introduction histories. Location California and Florida, USA. Methods We performed an ordination of ecological traits to confirm that ecologically similar species are indeed closely related phylogenetically. We then inferred molecular phylogenies for introduced and native reptiles using sequence data for two nuclear and three mitochondrial genes. Using these phylogenies, we computed two distance metrics: the mean phylogenetic distance (MPD) between each introduced species and all native species in each region (which indicates the potential interactions between introduced species and all native species in the community) and the distance of each introduced species to its nearest native relative – NN (indicating the degree of similarity and associated likelihood of competition between each introduced species and its closest evolutionary analogue). These metrics were compared for introduced species that established and those that failed. Results We demonstrate that phylogenetically related species do share similar ecological functions. Furthermore, successfully introduced species are more distantly related to natives (for NN and MPD) than failed species, although variation is high. Main conclusions The evolutionary history of a region has value for explaining and predicting the outcome of human‐driven introductions of reptiles. Phylogenetic metrics are thus useful inputs to multi‐factor risk assessments, which are increasingly required for screening introduced species.     

Is the distribution of nitrogen‐fixing cyanobacteria in the oceans related to temperature?

Approximately 50% of the global natural fixation of nitrogen occurs in the oceans supporting a considerable part of the new primary production. Virtually all nitrogen fixation in the ocean occurs in the tropics and subtropics where the surface water temperature is 25°C or higher. It is attributed almost exclusively to cyanobacteria. This is remarkable firstly because diazotrophic cyanobacteria are found in other environments irrespective of temperature and secondly because primary production in temperate and cold oceans is generally limited by nitrogen. Cyanobacteria are oxygenic phototrophic organisms that evolved a variety of strategies protecting nitrogenase from oxygen inactivation. Free-living diazotrophic cyanobacteria in the ocean are of the non-heterocystous type, namely the filamentous Trichodesmium and the unicellular groups A–C. I will argue that warm water is a prerequisite for these diazotrophic organisms because of the low-oxygen solubility and high rates of respiration allowing the organism to maintain anoxic conditions in the nitrogen-fixing cell. Heterocystous cyanobacteria are abundant in freshwater and brackish environments in all climatic zones. The heterocyst cell envelope is a tuneable gas diffusion barrier that optimizes the influx of both oxygen and nitrogen, while maintaining anoxic conditions inside the cell. It is not known why heterocystous cyanobacteria are absent from the temperate and cold oceans and seas.     

Is there a relationship between prion protein genotype and ovulation rate and litter size in sheep?

The identification of an association between polymorphisms of the prion protein (PrP) gene and susceptibility to scrapie has enabled the development of breeding programmes to increase natural resistance to scrapie. It is, however, imperative to identify if such selection would affect important reproduction and production traits. The objective of this study was to determine if there is a relationship between polymorphisms at codons 136, 154 and 171 of the PrP gene and ovulation rate or litter size in sheep. Data were collected from a mixed-aged flock of Belclare ewes, over a 9-year period. Ovulation rate was determined annually using laparoscopy by counting the number of corpora lutea at each of two consecutive oestrous cycles, one immediately before and one after mating (2418 records from 366 ewes). Litter size was recorded at parturition (875 records from 353 ewes). The five common PrP alleles were present in the population and 14 PrP genotypes were represented among the animals studied. There was no significant overall effect of PrP genotype on ovulation rate or litter size and pairwise comparisons among genotypes did not reveal any significant differences for either trait. These data suggest that breeding programmes based on selection for specific polymorphisms of the PrP gene will not influence ovulation rate or litter size, at least in the breed studied.     

Changes in the metabolic rate of the foraging honeybee: effect of the carried weight or of the reward rate?

The metabolic rate of free flying honeybees (Apis mellifera ligustica) foraging on a multiple automatic feeder was measured in complete absence of perturbation. Each time the sucrose flow rate was doubled, the metabolic rate increased by 18.2 ± 2.0% (14.7 μl CO₂ min⁻¹) and final crop load by 25.1 ± 2.4% (7.04 μl). The possibility that the heavier load carried by the bees caused the increase in the metabolic rate was analyzed in detail. It was found that, for the same weight in the crop, the metabolic rate increased with the increasing reward rate. Therefore, a factor other than the carried weight might account for this increase: a motivational drive, whose intensity may depend on the reward rate at the food source. Although at higher reward rates metabolic rate increased during the visit, at lower reward rates it remained constant, suggesting that the effect of the carried weight on the metabolic rate might be controlled by this motivational drive. The hypothesis that honeybees maximize individual efficiency by reducing their crop load loses support, as foraging costs are not determined by the carried weight. The functional meaning of the reduction in crop load would be to increase the informational exchange at the hive. Accepted: 8 January 2000     

Is orchid species richness and abundance related to the conservation status of oak forest?

The response of organisms to anthropogenic or natural modification of the environment is one of the most important questions in conservation biology and ecological theory. In spite of the fact that orchids are one of the most studied groups of plants, little information exists regarding their response to habitat alteration. The few existing studies are biased toward European orchid species and no consensus exists with regard to the response of orchids to human and natural disturbance. In this study, we sampled 30 transects (0.1 ha each) of oak forest located in Morelos, Central Mexico, and measured 13 variables related to forest aging and stump abundance, and six variables of orchid species richness and abundance. Neither abundance nor the richness and specific abundance of orchid genus or species were related to timber extraction. The abundance of dead standing trees in the forest, a surrogate variable of forest age, was positively related to abundance of orchids of the genus Malaxis, orchid richness and orchid abundance. This finding suggests that the conservation of all facets of the studied forest orchid community is dependent on natural processes (such as self-thinning) and the maintenance of older areas of the forest, and concurs with previous studies that suggest that natural disturbance is a key process for orchid survival.     

Is hissing behaviour of incubating great tits related to reproductive investment in the wild?

Anti-predator behaviour of breeding animals is a complex trait that depends on current reproductive investment as well as individual differences in risk-taking propensities. In response to nest predation, many bird species produce specific sounds, such as the hissing calls in incubating great tits (Parus major), that may provoke an acoustic startle response in the predator. However, it is still unclear whether the propensity of incubating females to produce hissing calls towards nest predators depends on the reproductive investment. With our 3-year study, we show that response type (females that do not hiss versus females giving hissing calls) to a potential nest predator, the woodpecker, is a repeatable trait. We found no differences in the studied reproductive traits between hissing and non-hissing birds. Interestingly, among hissing birds, fast-responding females started egg-laying earlier than slow-responding ones. Among non-hissing birds, heavier birds initiated clutches earlier. We also revealed that hissing birds breed in areas with decreased nest-box occupancy, suggesting either that they potentially select different areas to breed or that territory size is larger as a result of hissing birds being more aggressive. These findings demonstrate that response type is not related to the early reproductive value of the brood across distinct behavioural groups. However, our results do suggest that non-hissing and hissing females differ in terms of individual quality or dominance or personality related aspects.     

Is sociopolitical egalitarianism related to bodily and facial formidability in men?

Social bargaining models predict that men should calibrate their egalitarian attitudes to their formidability and/or attractiveness. A simple social bargaining model predicts a direct negative association between formidability/attractiveness and egalitarianism, whereas a more complex model predicts an association moderated by wealth. Our study tested both models with 171 men, using two sociopolitical egalitarianism measures: social dominance orientation and support for redistribution. Predictors included bodily formidability and attractiveness and four facial measures (attractiveness, dominance, masculinity, and width-to-height ratio). We also controlled for time spent lifting weights, and experimentally manipulated self-perceived formidability in an attempt to influence egalitarianism. Both the simple and complex social bargaining models received partial support: sociopolitical egalitarianism was negatively related to bodily formidability, but unrelated to other measures of bodily/facial formidability/attractiveness; and a formidability-wealth interaction did predict variance in support for redistribution, but the nature of this interaction differed somewhat from that reported in previous research. Results of the experimental manipulation suggested that egalitarianism is unaffected by self-perceived formidability in the immediate short-term. In sum, results provided some support for both the simple and complex social bargaining models, but suggested that further research is needed to explain why male formidability/attractiveness and egalitarianism are so often negatively related.     

Is branch damage by xylophages related to the presence of epiphytes?

Host identity influences the guilds (epiphytes and xylophages) that interact within canopies. Host species can be categorized as either limiting or preferred hosts based on epiphyte load. It is possible that, depending on the host category (limiting or preferred), galleries bored by xylophages would affect the quality and availability of space for epiphytes. The objective of this study was to determine, among and within limiting and preferred hosts, the relationship between the damage inflicted by insects to branches and epiphytic bromeliads. We collected two branches each (with and without epiphytes, respectively) from limiting hosts (Bursera fagaroides, Ipomoea murucoides and I. pauciflora) and preferred hosts (Bursera copallifera and B. glabrifolia). The variables measured were: number and species of epiphytes, number of holes, number and taxonomical group of insects, percentage of epiphyte cover and percentage of area damaged by insects. These variables were compared among and within hosts and the significant correlations, where present, determined. We identified five bromeliad species and six taxonomical groups of insects. I. murucoides showed a higher proportion of damage and a larger number of insects. For the three limiting hosts, there was a negative relationship between (1) epiphyte cover and damaged area, (2) number of epiphyte individuals and number of xylophages and (3) number of epiphyte individuals and damaged area. Within species, B. copallifera, B. glabrifolia and I. pauciflora had more holes in branches that supported epiphytes than in branches without. We hypothesized that, inter-specifically, xylophages would interfere with the establishment of epiphytes by facilitating the release of allelopathics, but this possibility needs to be examined in more detail. Intra-specifically, it is possible that holes made by xylophages do not cause sufficient damage in hosts and, consequently, a possible repercussion on epiphytes is not reflected.     

Is the large‐scale decline of the starling related to local changes in demography?

The decline of one farmland bird, the migratory European starling, has been attributed to both agricultural intensification and farmland abandonment and to factors operating both during the winter and during the breeding season. We analysed population data from thirty‐three Swedish nestbox colonies over more than two decades to determine if the national decline was caused by a common factor affecting all colonies or by local changes in the breeding grounds affecting starling colonies. We found that numbers of breeding starling had declined significantly, but at different rates in different colonies. The local population sizes were affected by previous years’ productivity at both national and local scales, suggesting that changes in habitat quality at both scales could affect local population trends. There were no long‐term trends in reproductive output, but fledgling production was lowest at intermediate years. The local population changes were positively related to local changes in reproductive output, but only when including complete nest‐failures. A relationship between population declines and low mean local productivity was the result of the association between population sizes and reproductive success over time, since decline rates of starlings were not related to the average success during the first part of the study, but to the average success during the later part of the study. The relationship between population change and changes in reproductive output was evident, but fledgling production showed negative density‐dependence. In conclusion this study suggests that the decline of the starling population in Sweden has been affected by processes at small spatial scales during the breeding season affecting reproductive success, but does not exclude an additional role for processes at large spatial scales or outside the breeding season.     

Is the strength of sea ice related to its chlorophyll content?

Summary Results of uniaxial compression test are compared to porosity and chlorophyll content of granular seaice samples, collected in the Weddell Sea from June to November of 1986. Compressive failure stresses are significantly correlated with the total porosity of the ice, but exhibit no correlation with chlorophyll concentration. We suggest that high chlorophyll concentrations may accompany low ice strengths only because high porosities, which are responsible for low mechanical strength, can be linked to sea-ice biology. High concentrations of ice algae may be either cause or effect of high porosities (through absorption of solar radiation in the first case or due to enhanced nutrient supply and environmental space in the second case). As a cause of high porosities, ice organisms could therefore indirectly influence the spring breakup of floes and thus the course of the ablation season.Contribution no. 411 from the Alfred-Wegener-Institute for Polar and Marine Research     

Hyponatremia: Is it related to the seasons?

BackgroundHyponatremia is a common electrolyte disorder in inpatients related to morbidity and mortality. In this study, we aimed to examine whether there is a relationship between the incidence of hyponatremia and the seasons among the patients hospitalized in our nephrology department.MethodsThe inpatients in our Nephrology Department between 2012 and 2015 were retrospectively analyzed. The patients with serum sodium levels below 135 mmol/L were included in the study. Hyponatremia incidence was calculated as the proportion of inpatients with low sodium levels in a season to the total number of inpatients in the same season.ResultsOut of 1950 inpatients in four years, 509 were found to have hyponatremia (26.1%). The mean serum sodium level of the patients was 129.7±4.7 mmol/L. Hyponatremia incidences in autumn, winter, spring, and summer were found to be 28.7%, 15.4%, 20.4%, and 36.6%, respectively. Upon comparing the incidence of hyponatremia in patients hospitalized in winter and summer seasons, there was a significantly higher incidence of hyponatremia in summer (p<0.001). We found a positive correlation between hyponatremia incidence and temperature (r=0.867, p=0.001). However, there was a negative correlation between hyponatremia incidence and relative humidity (r=-0.735, p=0.001).ConclusionsThe highest hyponatremia incidence was observed in summer in a four-year period. Loss of sodium by perspiration, along with increased temperature and/or excessive hypotonic fluid intake, might contribute to the development of hyponatremia.     

Is the lack of leguminous savanna trees in grasslands of South Africa related to nutritional constraints?

As with many grasslands globally, the Highveld grasslands of South Africa are tree-less, despite having a climate that can support tree growth. Models predict that fire maintains these grasslands. The question arises as to why fire-tolerant savanna trees do not survive in these ecosystems? Savanna tree survival in mesic areas is restricted by demographic bottlenecks, specifically limitations to sapling-escape from fire. It was hypothesised that ancient highly leached soils from grassland areas would prevent saplings from growing fast enough to escape the fire-trap. Growth rates of savanna tree seedlings (Acacia karroo Hayne and Acacia sieberiana Burtt Davy) were measured in a common garden experiment using soils from ten sites collected along a savanna-grassland continuum. Soils from grassland sites were relatively nutrient-poor compared to those from savannas with lower pH, and associated cations. A. sieberiana growth rates responded to pH and these nutrients, whereas A. karroo growth was less strongly linked to specific nutrients. Even so, both species accumulated more biomass when grown in soils from savanna sites compared to grassland sites. An exception was a low elevation low nutrient savanna site that resulted in poor growth, yet sustains high tree biomass in situ. Differences between growth in grassland and savanna soils were small. They may contribute to, but are unlikely to explain, the treeless nature of these grasslands.