The effects of wet wipe pollution on the Asian clam, Corbicula fluminea (Mollusca: Bivalvia) in the River Thames, London.

The aim of the present study was to evaluate "flushable" and "non-flushable" wet wipes as a source of plastic pollution in the River Thames at Hammersmith, London and the impacts they have on the invasive Asian clam, Corbicula fluminea, in this watercourse. Surveys were conducted to assess whether the density of wet wipes along the foreshore upstream of Hammersmith Bridge affected the distribution of C. fluminea. High densities of wet wipes were associated with low numbers of clams and vice versa. The maximum wet wipe density recorded was 143 wipes m-2 and maximum clam density 151 individuals m-2. Clams adjacent to the wet wipe reefs were found to contain synthetic polymers including polypropylene (57%), polyethylene (9%), polyallomer (8%), nylon (8%) and polyester (3%). Some of these polymers may have originated from the wet wipe reefs.

Constraint-Based Approach to Granular Dispersion Rheology.

We present a phenomenological model for granular suspension rheology in which particle interactions enter as constraints to relative particle motion. By considering constraints that are formed and released by stress respectively, we derive a range of experimental flow curves in a single treatment and predict singularities in viscosity and yield stress consistent with literature data. Fundamentally, we offer a generic description of suspension flow that is independent of bespoke microphysics.

Ingestion and fragmentation of plastic carrier bags by the amphipod Orchestia gammarellus: Effects of plastic type and fouling load.

Inappropriate disposal of plastic debris has led to the contamination of marine habitats worldwide. This debris can be ingested by organisms; however, the extent to which chewing and gut transit modifies plastic debris is unclear. Detritivores, such as amphipods, ingest and shred natural organic matter and are fundamental to its breakdown. Here we examine ingestion and shredding of plastic carrier bags by Orchestia gammarellus. A laboratory experiment showed these amphipods shredded plastic carrier bags, generating numerous microplastic fragments (average diameter 488.59µm). The presence of a biofilm significantly increased the amount of shredding, but plastic type (conventional, degradable and biodegradable) had no effect. Subsequent field observations confirmed similar shredding occurred on the strandline. Rates of shredding will vary according to amphipod density; however, our data indicates that shredding by organisms could substantially accelerate the formation microplastics in the environment.

Betamethasone-exposed preterm birth does not impair insulin action in adult sheep.

Preterm birth is associated with increased risk of type 2 diabetes (T2D) in adulthood; however, the underlying mechanisms are poorly understood. We therefore investigated the effect of preterm birth at ~0.9 of term after antenatal maternal betamethasone on insulin sensitivity, secretion and key determinants in adulthood, in a clinically relevant animal model. Glucose tolerance and insulin secretion (intravenous glucose tolerance test) and whole-body insulin sensitivity (hyperinsulinaemic euglycaemic clamp) were measured and tissue collected in young adult sheep (14 months old) after epostane-induced preterm (9M, 7F) or term delivery (11M, 6F). Glucose tolerance and disposition, insulin secretion, ß-cell mass and insulin sensitivity did not differ between term and preterm sheep. Hepatic PRKAG2 expression was greater in preterm than in term males (P = 0.028), but did not differ between preterm and term females. In skeletal muscle, SLC2A4 (P = 0.019), PRKAA2 (P = 0.021) and PRKAG2 (P = 0.049) expression was greater in preterm than in term overall and in males, while INSR (P = 0.047) and AKT2 (P = 0.043) expression was greater in preterm than in term males only. Hepatic PRKAG2 expression correlated positively with whole-body insulin sensitivity in males only. Thus, preterm birth at 0.9 of term after betamethasone does not impair insulin sensitivity or secretion in adult sheep, and has sex-specific effects on gene expression of the insulin signalling pathway. Hence, the increased risk of T2D in preterm humans may be due to factors that initiate preterm delivery or in early neonatal exposures, rather than preterm birth per se.

Assessing wave energy effects on biodiversity: the wave hub experience.

Marine renewable energy installations harnessing energy from wind, wave and tidal resources are likely to become a large part of the future energy mix worldwide. The potential to gather energy from waves has recently seen increasing interest, with pilot developments in several nations. Although technology to harness wave energy lags behind that of wind and tidal generation, it has the potential to contribute significantly to energy production. As wave energy technology matures and becomes more widespread, it is likely to result in further transformation of our coastal seas. Such changes are accompanied by uncertainty regarding their impacts on biodiversity. To date, impacts have not been assessed, as wave energy converters have yet to be fully developed. Therefore, there is a pressing need to build a framework of understanding regarding the potential impacts of these technologies, underpinned by methodologies that are transferable and scalable across sites to facilitate formal meta-analysis. We first review the potential positive and negative effects of wave energy generation, and then, with specific reference to our work at the Wave Hub (a wave energy test site in southwest England, UK), we set out the methodological approaches needed to assess possible effects of wave energy on biodiversity. We highlight the need for national and international research clusters to accelerate the implementation of wave energy, within a coherent understanding of potential effects-both positive and negative.

Sexual conflict and reproductive isolation in flies.

Sexual conflict is predicted to generate more rapid reproductive isolation between larger populations. While there is some empirical support for this, the data are inconsistent and, additionally, there has been criticism of some of the evidence. Here we reanalyse two experimental-evolution datasets using an isolation index widely applied in the speciation literature. We find evidence for reproductive isolation through sexual conflict in Sepsis cynipsea, but not in Drosophila melanogaster, and this occurred to a greater degree in larger populations, which is consistent with previous findings.

Genetic variation in strains of zebrafish (Danio rerio) and the implications for ecotoxicology studies.

There is substantial evidence that genetic variation, at both the level of the individual and population, has a significant effect on behaviour, fitness and response to toxicants. Using DNA microsatellites, we examined the genetic variation in samples of several commonly used laboratory strains of zebrafish, Danio rerio, a model species in toxicological studies. We compared the genetic variation to that found in a sample of wild fish from Bangladesh. Our findings show that the wild fish were significantly more variable than the laboratory strains for several measures of genetic variability, including allelic richness and expected heterozygosity. This lack of variation should be given due consideration for any study which attempts to extrapolate the results of ecotoxicological laboratory tests to wild populations.

Selfish genetic elements promote polyandry in a fly.

It is unknown why females mate with multiple males when mating is frequently costly and a single copulation often provides enough sperm to fertilize all a female's eggs. One possibility is that remating increases the fitness of offspring, because fertilization success is biased toward the sperm of high-fitness males. We show that female Drosophila pseudoobscura evolved increased remating rates when exposed to the risk of mating with males carrying a deleterious sex ratio-distorting gene that also reduces sperm competitive ability. Because selfish genetic elements that reduce sperm competitive ability are generally associated with low genetic fitness, they may represent a common driver of the evolution of polyandry.

Short-term rates of parasite evolution predict the evolution of host diversity.

Coevolution with parasites has been implicated as an important factor driving the evolution of host diversity. Studies to date have focussed on gross effects of parasites: how host diversity differs in the presence vs. absence of parasites. But parasite-imposed selection is likely to show rapid variation through time. It is unclear whether short-term fluctuations in the strength of parasite-imposed selection tend to affect host diversity, because increases in host diversity are likely to be constrained by both the supply of genetic variation and ecological processes. We followed replicate populations of coevolving, initially isogenic, bacteria and phages through time, measuring host diversity (with respect to bacterial colony morphologies), host density and rates of parasite evolution. Both host density and time-lagged rates of parasite evolution were good independent predictors of the magnitude of bacterial within- and between-population diversities. Rapid parasite evolution and low host density decreased host within-population diversity, but increased between-population diversity. This study demonstrates that short-term changes in the rate of parasite evolution can predictably drive patterns of host diversity.

Body size evolution in South American Liolaemus lizards of the boulengeri clade: a contrasting reassessment.

Bergmann's rule predicts larger body sizes in species living in higher latitudes and altitudes. This rule appears to be valid for endotherms, but its relevance to ectotherm vertebrates has largely been debated. In squamate reptiles (lizards and snakes), only one study, based on Liolaemus species of the boulengeri clade, has provided phylogenetic evidence in favour of Bergmann's clines. We reassessed this model in the same lizard clade, using a more representative measure of species body size and including a larger number of taxa in the sample. We found no evidence to support Bergmann's rule in this lineage. However, these non-significant results appear to be explained only by the inclusion of further species rather than by a different estimation of body size. Analyses conducted on the 16 species included in the previous study always revealed significant relationships between body size and latitude-altitude, whereas, the enlarged sample always rejected the pattern predicted by Bergmann's rule.

Sperm competition promotes the exploitation of rival ejaculates.

In many polyandrous species, the second male to mate with a female has fertilization priority. Strategic mechanisms generating this pattern tend to involve facultative increases in ejaculate size by informed males. Here we suggest a novel mechanism to generate second male precedence in internal fertilizers, based on the established fact that the female site of insemination is hostile to sperm, and that non-sperm components of the ejaculate frequently act to ameliorate these hostile conditions. We suggest that in species where female remating is frequent and rapid, second male sperm precedence may be due to the prior buffering of the female tract by previous males' ejaculates. In this scenario, second male costs are lower due to reduced sperm mortality and/or the redundancy of seminal fluid. Contrary to many classical predictions, second males may gain a paternity advantage despite investing less in an ejaculate.

Host ecology determines the relative fitness of virus genotypes in mixed-genotype nucleopolyhedrovirus infections.

Mixed-genotype infections are common in many natural host-parasite interactions. Classical kin-selection models predict that single-genotype infections can exploit host resources prudently to maximize fitness, but that selection favours rapid exploitation when co-infecting genotypes share limited host resources. However, theory has outpaced evidence: we require empirical studies of pathogen genotypes that naturally co-infect hosts. Do genotypes actually compete within hosts? Can host ecology affect the outcome of co-infection? We posed both questions by comparing traits of infections in which two baculovirus genotypes were fed to hosts alongside inocula of the same or a different genotype. The host, Panolis flammea, is a herbivore of Pinus sylvestris and Pi. contorta. The pathogen, PfNPV (a nucleopolyhedrovirus), occurs naturally as mixtures of genotypes that differ, when isolated, in pathogenicity, speed of kill and yield. Single-genotype infection traits failed to predict the 'winning' genotypes in co-infections. Co-infections infected and caused lethal disease in more hosts, and produced high yields, relative to single-genotype infections. The need to share with nonkin did not cause fitness costs to either genotype. In fact, in hosts feeding on Pi. sylvestris, one genotype gained increased yields in mixed-genotype infections. These results are discussed in relation to theory surrounding adaptive responses to competition with nonkin for limited resources.

Food-plant effects on larval performance do not translate into differences in fitness between populations of Panolis flammea (Lepidoptera: Noctuidae).

In the UK, Panolis flammea (Denis & Schiffermüller) is a pest of monocultures of non-native lodgepole pine Pinus contorta Douglas, but not of the indigenous host Scots pine P. sylvestrisL. This difference in population dynamics may be due to the adaptation of P. flammea populations to the phenology, chemical composition and natural enemy complement of lodgepole pine. To ascertain if there was local adaptation of P. flammea populations to lodgepole pine, this study tested for improved performance of both larvae and adults on the host plant species from which they were sourced, compared with their performance on the alternative host plant species. No difference was found in the relative mean performance of populations sourced from Scots pine or lodgepole pine plantations, when fed on Scots or lodgepole pine foliage. Larvae grew faster on Scots pine but this difference did not translate into differences in pupal weight, female body weight or fecundity. Indeed, those insects that had fed on lodgepole pine had a longer lifespan than those that had fed on Scots pine, which, if translated into greater probability of mating or higher fecundity, could contribute to the observed outbreak dynamics in the field. The prediction that the observed outbreak dynamics of P. flammea can be explained by the existence of populations locally adapted to lodgepole pine was not supported. These results cast doubt on the use of larval growth parameters as surrogates of fitness in Lepidoptera.

The consequences of clustering by Aphis fabae foundresses on spring migrant production.

Aphis fabae (Homoptera: Aphididae) foundresses were shown to have a clustered distribution on leaves of their primary host, Euonymus europaeus. Two field experiments were carried out to determine the costs or benefits of this clustering behaviour to aphid clones. The first experiment, in spring 1996, excluded predators from colonies formed by single fundatrices or clusters of three. No density-dependent effects on colony growth were observed early in the season, but the total production of migrants per foundress was significantly lower for clustered foundresses. This demonstrated that there was no synergistic effect of group feeding on clonal performance. All colonies were initiated on randomly selected leaves and all grew successfully, therefore clustering was not due to a shortage of feeding sites. The second experiment, in spring 1997, tested whether natural enemies cause selection for selfish herding by the foundress generation. Colonies were initiated by one or three foundresses, but half were left unbagged. If natural enemy attack is a selective force inducing clustering behaviour in foundresses, the costs of clustering should have been reduced or negated in unbagged colonies. Colonies grown from clusters produced significantly fewer migrants per foundress, irrespective of bagging treatment. Other potential factors causing clustering behaviour are discussed.

The relationship between power output and endurance: a brief review.

It is well established that for work requiring high power output, endurance time is short, and that low power outputs can be maintained for long periods. Parameters describing this relationship are important in characterising work performance and the capacity of humans as a source of mechanical power. The purpose of this paper is to provide a brief review of the available literature investigating this relationship and its parameters. Most experimental data reflect measurements of endurance times over a range of constant power outputs on the cycle ergometer. Early graphical analyses of these data have been superseded by curve fitting, which in turn has led to establishment of the two component hyperbolic model now embodied in the critical power test. This model has been modified and extended in various ways to account for its shortcomings. In addition, a number of different exercise forms have been studied, and the effects of a variety of secondary factors (training status, age, sex, for example) on the parameters have also been investigated.

Conformation and structure of acidic dipeptides. Crystal structures of L-alanyl-L-aspartic acid and alpha-L-glutamyl-L-aspartic acid.

The crystal structures of the dipeptides L-alanyl-L-aspartic acid, C7H12N2O5, and alpha-L-glutamyl-L-aspartic acid, C9H14N2O7, have been determined from three-dimensional X-ray diffractometer data. Alanylaspartic acid crystallizes in the orthorhombic space group P2(1)2(1)2(1) with four formula units in a cell of dimensions a = 13.389(5), b = 14.467(3), c = 4.781(1) A. Glutamylaspartic acid also crystallizes in space group P2(1)2(1)2(1) with four formula units in a cell of dimensions a = 13.709(5), b = 16.126(7), c = 4.939(5) A. Both structures were solved by direct methods and refined by full-matrix least squares methods; the final value of the weighted R-factors (on F) were 0.040 based on 790 independent intensities with I greater than or equal to 2 sigma (I) for Ala-Asp and 0.033 based on 1105 intensities with I greater than or equal to 2 sigma (I) for Glu-Asp. Each dipeptide occurs as a zwitterion with the amino terminus protonated and the main chain carboxyl group deprotonated. The conformation of the peptide linkage is trans in both molecules, the omega torsion angle being - 175.9 degrees in Ala-Asp and 174.3 degrees in Glu-Asp. There is considerable intermolecular, but not intramolecular, hydrogen bonding in the crystals. The conformations and structures of Ala-Asp and Glu-Asp are compared to those of other structurally characterized acidic dipeptides.

Conformation and crystal structure of L-prolyl-L-glutamic acid dihydrate.

The crystal structure of the dipeptide L-prolyl-L-glutamic acid dihydrate, L-Pro-L-Glu . 2H2O, C10H20O7N2, has been determined from three-dimensional X-ray diffractometer data. The dipeptide crystallizes in the space group P21 of the monoclinic system with two formula units in a cell of dimensions a = 5.629(2), b = 11.832(5), c = 10.485(4)A, and beta = 103.06(3) degrees. The structure was solved by direct methods and refined by least squares techniques to a final value of the conventional R-factor (on F) of 0.039 based on 1798 independent intensities with I greater than or equal to 3 sigma(I). The dipeptide occurs as a zwitterion in the crystal with the pyrrolidine nitrogen atom protonated and the main chain carboxyl group deprotonated. The conformation of the peptide linkage is trans, the omega torsional angle being 173.7 degrees. The pyrrolidine ring adopts the Cs-C beta endo conformation and the conformation of the glutamyl side chain is fully extended. There is considerable intermolecular hydrogen bonding in the crystals.

Conformation and structure of acidic dipeptides. Crystal structure of glycyl-L-aspartic acid dihydrate.

The crystal structure of the acidic dipeptide glycyl-L-aspartic acid dihydrate, Gly-L-Asp X 2H2O, C6H10N2O5 X 2H2O, has been determined by means of three-dimensional counter X-ray data. The dipeptide crystallizes in space group P212121 of the orthorhombic system with four formula units in a cell of dimensions of a = 9.611(4), b = 9.775(6), and c = 10.845(4)A. The structure was solved by direct methods and refined by least-squares methods to a final value of the weighted R-factor of 0.035 using all 1191 observed intensity data. The dipeptide occurs in the crystal as a zwitterion, with the glycyl N-terminus protonated and the aspartyl main chain carboxyl group deprotonated. The conformation about the peptide bond is fully trans extended, with an omega angle of -175.9 degrees. While there is extensive intermolecular hydrogen bonding in the crystals, there is no intramolecular hydrogen bonding either here or in the solid state structures of related dipeptides.