Interspecies variation in yolk selenium concentrations among eggs of free-living birds: The effect of phylogeny

Birds deposit the trace element selenium (Se) into their eggs because an adequate supply of this micronutrient is essential for embryonic development. Although there is considerable interest in egg Se with regard to topics as diverse as poultry nutrition and environmental pollution, data on the natural levels of Se in eggs of free-living avian species are currently very limited. To address this lack of information, we measured the yolk Se concentrations in eggs of 14 avian species collected in the wild. The concentrations (ng/g wet yolk) varied from 394 to 2238, with a mean value of 1040. Values (means+/-SD) for eggs from the UK, Canada and New Zealand were, respectively, 522+/-192 (3 species), 1194+/-584 (8 species) and 1147+/-200 (3 species). However, analysis by appropriate statistical models indicates that the effect of phylogenetic relatedness among these species is so significant that it removes any effect of geographical location. In particular, species belonging to the order Passeriformes displayed significantly higher yolk Se levels than Non-Passeriforme species. In marked contrast to the free-living species, our previously published data indicate that the Se concentration in egg yolk of the domestic chicken is only about 100 ng/g wet yolk when the birds are maintained on a basal commercial diet without supplementary Se. The results reveal an extensive interspecies variation in yolk Se (across a 6-fold range) for eggs collected from the wild. Nevertheless, the Se concentrations in the yolks of all the free-living species were far higher (4-21-fold) than that achieved in the yolk of the domestic chicken consuming a standard basal diet.     

Revised evidence for facultative sex ratio adjustment in birds: a correction

We provide a revision to the calculation of effect sizes and heterogeneity statistics in our original article, 'Facultative primary sex ratio variation: a lack of evidence in birds' (Ewen et al. 2004). Our revision shows that significant heterogeneity in sex ratio study effect sizes does indeed exist and that for a series of key traits the average effect sizes (while still weak) are in fact significantly different from zero.     

Enhanced astaxanthin production from microalga,Haematococcus pluvialis by two-stage perfusion culture with stepwise light irradiation

For efficient astaxanthin production from the culture of green microalga, Haematococcus pluvialis, a two-stage mixotrophic culture system was established with stepwise increased light irradiance. By perfusion process, high density biomass (2.47 g/L) was achieved during the vegetative stage due to no detrimental effect of inhibitory metabolites, which was 3.09 and 1.67 times higher than batch and fed-batch processes, respectively. During the induction stage, biomass and astaxanthin were subsequently produced to the very high level 12.3 g/L and 602 mg/L, under stepwise increased light irradiance (150–450 μE/m²/s), respectively. These results indicate that the combinatorial approach of perfusion culture during the vegetative stage and stepwise light irradiation during the induction stage is a promising strategy for the simultaneous production of high concentration of biomass and astaxanthin in microalgae including H. pluvialis.     

Phenotypic variation and promiscuity in a wild population of pure dingoes (Canis dingo)

Phenotypic diversity occurs in natural populations as a result of the interaction between an individual's genotype and the environment. Nevertheless, individual variation in phenotypic traits such as coat colour and body size is routinely used to differentiate between “pure” dingoes Canis dingo and dingo‐dog hybrids. Extensive anthropogenic impacts and widespread hybridization with domestic dogs has hindered our ability to study intact dingo populations and, therefore, most of our basic understanding of dingo biology (e.g., phenotypic variation, mating systems, genetic diversity) stems from observational studies on perturbed populations. We sampled a relatively undisturbed population of dingoes, from arid Australia, to determine their purity and genetic diversity. We explored their mating strategy using a pedigree built from genetic data and examined how phenotypic variation was influenced by age, sex, heterozygosity, and relatedness. Coat colour was our measure of phenotype and our population displayed four types (sandy, black & tan, white, and sable). All dingoes (n = 83) possessed a high level of dingo ancestry (mean purity > 90%) and were closely related to each other; with all but one individual related as full‐sibling or parent–offspring. Our pedigree shows both monogamous and promiscuous mating strategies exist within an undisturbed population. Variation in coat colour or body size cannot be used to infer a dingo's level of purity because the phenotype of pure dingoes is intrinsically variable. The breeding system of dingoes was long thought to be monogamous, but we provide genetic evidence for numerous mating strategies including both long‐term monogamy and extreme promiscuity.     

Adaptive Sampling of Information in Perceptual Decision-Making

In many perceptual and cognitive decision-making problems, humans sample multiple noisy information sources serially, and integrate the sampled information to make an overall decision. We derive the optimal decision procedure for two-alternative choice tasks in which the different options are sampled one at a time, sources vary in the quality of the information they provide, and the available time is fixed. To maximize accuracy, the optimal observer allocates time to sampling different information sources in proportion to their noise levels. We tested human observers in a corresponding perceptual decision-making task. Observers compared the direction of two random dot motion patterns that were triggered only when fixated. Observers allocated more time to the noisier pattern, in a manner that correlated with their sensory uncertainty about the direction of the patterns. There were several differences between the optimal observer predictions and human behaviour. These differences point to a number of other factors, beyond the quality of the currently available sources of information, that influences the sampling strategy.     

A nondestructive method for extracting maternally derived egg yolk carotenoids

ABSTRACT.   Maternally deposited carotenoids are a prominent component of egg yolk and are vital for the development and growth of the embryo. In most studies of avian yolk carotenoids, eggs are destructively sampled and this may limit both the number of clutches studied and the research questions addressed. We describe an empirical field trial for a nondestructive biopsy method to extract small samples (0.05 ml) of egg yolk for high-performance liquid chromatography (HPLC) analysis of yolk carotenoid concentrations. We sampled 180 clutches ( N = 44 biopsies) of two species of introduced thrushes (genus Turdus ) from agricultural habitats in central North Island, New Zealand. Once the protocol was established, all biopsied eggs from clutches that were not depredated or deserted before candling were found to be developing normally after 3–5 d of incubation ( N = 28) and all hatched. Biopsy samples (>0.02 g) produced concentrations of yolk carotenoids (and variances) that were statistically indistinguishable from whole yolk destructive samples. In addition, our samples (>0.02 g) confirmed previously reported differences in yolk carotenoid concentrations between the two thrush species and revealed a significant decline in yolk carotenoid concentration with laying order. Further examination of how variability in yolk carotenoid concentration and identity influences offspring sex, success, and survival or, later in life, reproductive success and ability to efficiently incorporate dietary carotenoids into both integument and immune tissues will require larger sample sizes. Studies to date have been restricted by the number of destructive samples that investigators are willing (or permitted) to obtain from wild species. Thus, we hope that our nondestructive method of sampling yolk will promote further examination of the links between carotenoid uptake from the environment and maternal investment in the avian yolk.     

Novel piperidinium and pyridinium agents as water-soluble acetylcholinesterase inhibitors for the reversal of neuromuscular blockade

A series of piperidinium and pyridinium agents containing a common structural fragment of 5,6-dimethoxybenzothiophene have been synthesised as water-soluble acetylcholinesterase inhibitors. Several compounds, for example 42 (AChE IC(50) 0.03 microM) have been found to reverse the neuromuscular blockade induced by vecuronium bromide in vitro and in vivo. Coupled with their high water solubility (up to 30-60 mg/mL), these compounds are potentially useful as intravenous reversal agents of neuromuscular blocking agents in surgical anaesthesia.     

Biomechanical implications of degenerative joint disease in the apophyseal joints of human thoracic and lumbar vertebrae

An experimental technique for quantifying load-sharing in cadaveric spines is used to test the hypothesis that degenerative changes in human apophyseal joints are directly related to high levels of compressive load-bearing by these joints. About 36 cadaveric thoraco-lumbar motion segments aged 64-92 years were subjected to a compressive load of 1.5 kN. The distribution of compressive stress was measured in the intervertebral discs using a miniature pressure transducer, and stress measurements were summed over area to give the compressive force resisted by the disc. This was subtracted from the applied 1.5 kN to indicate compressive load-bearing by the apophyseal joints. The cartilage of each apophyseal joint surface was then graded for degree of degeneration. After maceration, each joint surface was scored for degenerative joint disease (DJD) affecting the bone. Results demonstrated that the apophyseal joints resisted 5-96% (mean 45%) of the applied compressive force. A significant positive correlation was demonstrated between age and cartilage degeneration, age and DJD bone score, apophyseal joint load-bearing and bone score, and cartilage score and load-bearing. The latter correlation was strongest for load-bearing above 50%. Ordinal regression showed that the variables describing bone DJD (marginal osteophytes, pitting, bony contour change, and eburnation) were significantly correlated with degree of cartilage degeneration. It is concluded that in elderly individuals apophyseal joint load-bearing above a threshold of 50% is associated with severe degenerative changes in cartilage and bone, and that markers of DJD observed palaeopathologically may be used as predictors of such loadingin life.     

The varying role of population abundance in structuring indices of biotic homogenization

Aim An important component of human‐induced global change is the decrease or increase in community distinctiveness (taxonomic homogenization or differentiation, respectively) that follows the loss of native species and gain of non‐native species. We use simulation approaches to assess the extent to which conclusions about the outcome of the homogenization process depend on whether or not abundance data are incorporated. Location Data were produced through computer simulation. Methods The frequency with which occurrence‐based similarity indices and abundance‐based similarity indices give different views of changes in community similarity, and the conditions under which such differences occurred were assessed using both deterministic and stochastic modelling approaches to simulate species assemblage states. Results Occurrence‐based and abundance‐based indices were positively correlated across the set of simulations for both the deterministic and stochastic models. However, in both situations approximately one quarter (25%) of models resulted in contrasting outcomes for the two approaches of calculating changes in compositional similarity; that is, one data type showed a positive value (homogenization), whereas the other showed a negative value (differentiation). Main conclusions In the majority of cases, species abundances will not change drastically enough after perturbation to produce large differences between homogenization scores measured using occurrence versus abundance information. However, in cases where these changes are large, it is important to recognize that the choice of metric to analyse homogenization trends will influence the qualitative and quantitative conclusions drawn. Studies of real assemblages are therefore necessary to evaluate the role of species abundance in defining the magnitude and direction of changes in community composition across space, and the implications of these changes for native biodiversity.     

The island biogeography of exotic bird species

Aim   A recent upsurge of interest in the island biogeography of exotic species has followed from the argument that they may provide valuable information on the natural processes structuring island biotas. Here, we use data on the occurrence of exotic bird species across oceanic islands worldwide to demonstrate an alternative and previously untested hypothesis that these distributional patterns are a simple consequence of where humans have released such species, and hence of the number of species released.
Location   Islands around the world.
Methods   Statistical analysis of published information on the numbers of exotic bird species introduced to, and established on, islands around the world.
Results   Established exotic birds showed very similar species–area relationships to native species, but different species–isolation relationships. However, in both cases the relationship for established exotics simply mimicked that for the number of exotic bird species introduced. Exotic bird introductions scaled positively with human population size and island isolation, and islands that had seen more native species extinctions had had more exotic species released.
Main conclusion   The island biogeography of exotic birds is primarily a consequence of human, rather than natural, processes.