Does green light influence the fluorescence properties and structure of phototrophic biofilms?

Artificial illumination can harm works of art by inducing the development of photosynthetic biofilms. With the aim of preventing biodeterioration or esthetic damage to such surfaces, we evaluated and compared the effects of illuminating biofilms formed by Gloeothece membranacea (cyanobacteria) and Chlorella sorokiniana (Chlorophyta) using exclusively white or green light.     

Do predators influence the behaviour of bats?

Many aspects of animal behaviour are affected by real‐time changes in the risk of predation. This conclusion holds for virtually all taxa and ecological systems studied, but does it hold for bats? Bats are poorly represented in the literature on anti‐predator behaviour, which may reflect a lack of nocturnal predators specialized on bats. If bats actually experience a world with minimal anti‐predator concerns, then they will provide a unique contrast within the realm of vertebrate ecology. Alternatively, such predator‐driven behaviour in bats may not yet be fully understood, given the difficulties in working with these highly mobile and nocturnal animals. We provide a wide‐ranging exploration of these issues in bat behaviour. We first cover the basic predator‐prey information available on bats, both on potential predators and the ways in which bats might perceive predators and respond to attacks. We then cover work relevant to key aspects of bat behaviour, such as choice of daytime roosts, the nature of sleep and torpor, evening roost departures, moonlight avoidance, landscape‐related movement patterns, and habitat selection. Overall, the evidence in favour of a strong influence of predators on bat behaviour is equivocal, with the picture clouded by contradictory results and a lack of information on potential predators and the perception of risk by bats. It seems clear that day‐active bats run a considerable risk of being killed by diurnal raptors, which are able to capture bats with relative ease. Thus, bats taking advantage of a pulse of insects just prior to sunset are likely taking risks to gain much‐needed energy. Further, the choice of daytime roosts by bats is probably strongly influenced by roost safety. Few studies, however, have directly addressed either of these topics. As a group, insectivorous temperate‐zone bats show no clear tendency to avoid apparently risky situations, such as activity on moonlit nights. However, some observations are consistent with the idea that predation risk affects choice of movement paths and feeding areas by temperate‐zone bats, as well as the timing of roost departures. The behaviour of tropical bats, on the other hand, seems more generally influenced by predators; this is especially true for tropical nectarivores and frugivores, but also for insectivorous bats. Presumably there are more serious predators on bats in the tropics (e.g. specialized raptors or carnivorous bats), but the identity of these predators is unclear. More information is needed to assess fully the influence of predators on bat behaviour. There is much need for work on the ways in which bats perceive predators via auditory, visual, and olfactory cues, and whether bats have some knowledge of the risks posed by different predators. Also needed is information on how predators attack bats and how bats react to attacking predators. Difficult to obtain, but of critical value, will be information on the nature of the predation risk experienced by bats while away from roosts and during the full darkness of night.     

How does the presence of predators influence the persistence of antipredator behavior?

We developed a virtual world to study the effect of predators on predator recognition. We trained a neural network to discriminate between the shapes of simulated aerial and terrestrial predators and non-predators. Then, the network's weighting values were fixed into the genomes of a set of autonomous agents. These animats were required to eat, avoid death due to starvation, and avoid predation, by fleeing from approaching predators. We systematically varied the predator's lethality, the mutation rate, the cost of fleeing a predator, and the presence or absence of aerial and terrestrial predators. We used ANOVA to analyse the average recognition ability (a measure of directional selection) and the standard deviation of recognition ability (a measure of relaxed selection) after 500 generations of selection. Mutation rate and the cost of flight had the greatest effect on both the average and standard deviation of recognition abilities. The loss of all predators relaxed selection on predator recognition abilities. The loss of specific predators had complex effects on recognition abilities. Persistence is largely influenced by escape costs.     

Do predatory drill holes influence the transport and deposition of gastropod shells?

Predatory gastropod drill holes are an abundant and easily identifiable signal of predation in ancient and modern molluscan shell assemblages. Many workers have used drill holes to interpret patterns of predation intensity and success in fossil assemblages. These studies are predicated on the assumption that the relative abundances of drilled and undrilled shells in an assemblage accurately reflect those of the community from which the shells were originally derived. The underlying assumption is that drilled and undrilled shells are transported into shell accumulations in the same manner. If this assumption is false, shell accumulations do not represent taphonomically unbiased samples, but rather preferentially sorted deposits from which conclusions about drilling predation cannot be made. To test the hypothesis that drilled and undrilled gastropod shells transport at different flow velocities, multiple transport trials were conducted on two morphologically distinct taxa, Olivella biplicata and Euspira lewisii. Individual specimens were placed in a recirculating flume tank and observed from rest (in stable orientation) until they were transported downstream. During each trial, flow velocity was slowly and incrementally increased, so as to avoid pulses of acceleration, until shells began to move downstream. Drilled and undrilled specimens of both taxa demonstrate statistically significant correlations between shell mass and average transport velocity. Similarly sized drilled and undrilled specimens of both taxa do not exhibit significant differences in transport velocity. These results indicate that predatory drill holes do not change the hydrodynamic properties of gastropod shells. Therefore, gastropod shell assemblages are not likely to be affected by differential transport and sorting of drilled and undrilled shells.     

Do biodiversity and human impact influence the introduction or establishment of alien mammals?

What determines the number of alien species in a given region? ‘Native biodiversity’ and ‘human impact’ are typical answers to this question. Indeed, studies comparing different regions have frequently found positive relationships between number of alien species and measures of both native biodiversity (e.g. the number of native species) and human impact (e.g. human population). These relationships are typically explained by biotic acceptance or resistance, i.e. by influence of native biodiversity and human impact on the second step of the invasion process, establishment. The first step of the invasion process, introduction, has often been ignored. Here we investigate whether relationships between number of alien mammals and native biodiversity or human impact in 43 European countries are mainly shaped by differences in number of introduced mammals or establishment success. Our results suggest that correlation between number of native and established mammals is spurious, as it is simply explainable by the fact that both quantities are linked to country area. We also demonstrate that countries with higher human impact host more alien mammals than other countries because they received more introductions than other countries. Differences in number of alien mammals cannot be explained by differences in establishment success. Our findings highlight importance of human activities and question, at least for mammals in Europe, importance of biotic acceptance and resistance.     

Do food protein and carbohydrate content influence the pattern of feeding and the tendency to explore of forest tent caterpillars?

This study examines whether the ratio of protein to carbohydrate affects the timing of meals and the propensity to explore of forest tent caterpillars (Malacosoma disstria). The behavior of fourth instar caterpillars was observed on three semi-defined artificial diets varying in protein (p)-carbohydrate (c) ratio. These diets were (a) p14:c28, (b) p28:c14, and (c) p35:c7. The probability of initiating feeding at first contact with the food and the duration of the first feeding event did not vary across diets, suggesting not much difference in phagostimulatory power. There was also no difference in the total time spent eating, at rest and in motion between diets. However, the timing and duration of meals varied significantly; more short meals were observed on the carbohydrate-biased diet. The duration of pauses between meals also increased with food protein content. Furthermore, caterpillars on the carbohydrate-biased diet were more likely to leave the trail leading to the known food source and to discover a second food source, suggesting that protein deprivation promotes exploration. These findings shed insight into the physiological responses to protein and carbohydrate ingestion and demonstrate how post-ingestive effects can favor consumption of foods containing protein without invoking an explicit mechanism of independent nutrient regulation, but simply by influencing the pattern of feeding and the propensity to explore.     

Can pesticide formulations significantly influence pest behavior?: the case of Tetranychus urticae and dicofol

Pesticide formulations profoundly influenced the encounter of pest with pesticide. In four differently formulated treatments of identical dicofol concentration, total time spent on treated areas of a checkerboard residue immediately following treatment varied dramatically from 13.3% on Modified Formulation residues to 42.1 % on 50 Wettable Powder residues. With 24 h old checkerboard residues, total time spent on treated areas varied from a low of 30.1% with Modified Formulation residues to a high of 45.1% with Emulsifiable Concentrate residues. Different formulations exhibited dramatically different decay of repellency over a 24 h period. The greatest loss of repellency was found on Modified Formulation residues, although this formulation was still the most repellent at 24 h. Observations were made of three behavior patterns with both 0 h and 24 h old residues of four formulations of dicofol. Our results indicate that the constituents of some pesticide formulations may elicit behavior that greatly reduces pest encounter with pesticide. To study this phenomenon it is necessary to observe pest behavior with discontinuous residues.     

Do mesocosms influence photosynthesis and soil respiration?

Mesocosms, enclosed outdoor experimental systems, are commonly used in terrestrial ecology. They are frequently used to study the effects of elevated CO₂ and temperature on terrestrial ecosystem processes. Despite their advantages and frequent use it is important to verify, through explicit measures, that mesocosms reliably model the larger system. In this study, fully-coupled, soil–litter–plant mesocosms were constructed in Corvallis using native soil and litter, and planted with Douglas-fir (Pseudotsuga menziesii Mirb. Franco) seedlings. Needle photosynthesis and soil respiration were measured repeatedly over a 21-month period in mesocosms and compared to measurements made at two field sites (Toad Creek and Falls Creek) planted at the same density as the mesocosms. Under the temperature and soil moisture conditions, photosynthetic and soil respiration rates in the mesocosms were not significantly different than the rates at Toad Creek, where the soil and litter in the mesocosms were collected. In contrast, the soil at Falls Creek was different than the soil in the mesocosms and at Toad Creek and photosynthetic and soil respiration rates at Falls Creek were significantly different than at the other two sites. The lack of significant differences between rates measured in the mesocosms in Corvallis and at the Toad Creek field site indicate that the mesocosms did not cause significant artifacts in the data and that the results for these rates in the mesocosms can be extrapolated to field settings with comparable edaphic conditions.     

Do pollinators influence the assembly of flower colours within plant communities?

The co-occurrence of plant species within a community is influenced by local deterministic or neutral processes as well as historical regional processes. Floral trait distributions of co-flowering species that share pollinators may reflect the impact of pollinator preference and constancy on their assembly within local communities. While pollinator sharing may lead to increased visitation rates for species with similar flowers, the receipt of foreign pollen via interspecific pollinator movements can decrease seed set. We investigated the pattern of community flower colour assembly as perceived by native honeybee pollinators within 24 local assemblages of co-flowering Oxalis species within the Greater Cape Floristic Region, South Africa. To explore the influence of pollinators on trait assembly, we assessed the impact of colour similarity on pollinator choices and the cost of heterospecific pollen receipt. We show that flower colour is significantly clustered within Oxalis communities and that this is not due to historical constraint, as flower colour is evolutionarily labile within Oxalis and communities are randomly structured with respect to phylogeny. Pollinator observations reveal that the likelihood of pollinators switching between co-flowering species is low and increases with flower colour similarity. Interspecific hand pollination significantly reduced seed set in the four Oxalis species we investigated, and all were dependant on pollinators for reproduction. Together these results imply that flower colour similarity carries a potential fitness cost. However, pollinators were highly flower constant, and remained so despite the extreme similarity of flower colour as perceived by honeybees. This suggests that other floral traits facilitate discrimination between similarly coloured species, thereby likely resulting in a low incidence of interspecific pollen transfer (IPT). If colour similarity promotes pollinator attraction at the community level, the observed clustering of flower colour within communities might result from indirect facilitative interactions.     

Ain't misbehavin' ? Genotype-environment interactions and the genetics of behavior

Although the multiple interacting genes affecting complex traits can readily be dissected, how much genotype-environment interactions contribute to variation in complex traits remains elusive. A recent study that quantified several behavioral phenotypes on the same mouse strains in different laboratories decades apart, shows that some behavioral differences between laboratories remain greatly replicable, whereas others are less robust over time. This report, together with studies from Drosophila, stresses the importance of understanding genotype-environment interactions.     

Do oral bacteria alter the regenerative potential of stem cells? A?concise review

Mesenchymal stem cells (MSCs) are widely recognized as critical players in tissue regeneration. New insights into stem cell biology provide evidence that MSCs may also contribute to host defence and inflammation. In case of tissue injury or inflammatory diseases, e.g. periodontitis, stem cells are mobilized towards the site of damage, thus coming in close proximity to bacteria and bacterial components. Specifically, in the oral cavity, complex ecosystems of commensal bacteria live in a mutually beneficial state with the host. However, the formation of polymicrobial biofilm communities with pathogenic properties may trigger an inadequate host inflammatory‐immune response, leading to the disruption of tissue homoeostasis and development of disease. Because of their unique characteristics, MSCs are suggested as crucial regulators of tissue regeneration even under such harsh environmental conditions. The heterogeneous effects of bacteria on MSCs across studies imply the complexity underlying the interactions between stem cells and bacteria. Hence, a better understanding of stem cell behaviour at sites of inflammation appears to be a key strategy in developing new approaches for in situ tissue regeneration. Here, we review the literature on the effects of oral bacteria on cell proliferation, differentiation capacity and immunomodulation of dental‐derived MSCs.     

Do seasonally fluctuating aquatic subsidies influence the distribution pattern of birds between riparian and upland forests?

Seasonal fluctuation of allochthonous subsidies influences food web structure and dynamics in recipient communities. This study investigated whether aquatic subsidies influence the dynamics of insectivorous birds in entire catchment. We estimated the prey biomass and bird density in riparian and upland habitats in three catchments in temperate deciduous forests in Hokkaido, Japan. Aquatic prey was found only in riparian forests and the biomass peaked in early spring, while terrestrial prey was equally distributed between habitats and increased in biomass in late spring. Bird density was higher in riparian than in upland forests before bud break, when the biomass of aquatic insects peaked, but was similar in both forests during the rest of the seasons. These results suggest that aquatic prey subsidies are used not only by birds inhabiting riparian forests, but also by birds associated with upland forests. Aquatic prey subsidies may be particularly important in the spring as a critical food resource for survival and the breeding activities of birds, thereby, influencing the population dynamics of bird communities.     

Do submerged aquatic plants influence their periphyton to enhance the growth and reproduction of invertebrate mutualists?

It has been suggested that submerged aquatic plants can influence the nutritional quality of the periphyton which grows on their surfaces, making it more nutritious for grazing invertebrates, particularly snails. In return, these grazers might preferentially feed on the periphyton and clear the plants of a potential competitor, with the plants and grazers both gaining from this mutualistic relationship. A highly replicated experiment was conducted, in which the nature of the plant (isoetid and elodeid types compared with similar-shaped inert substrata), the nutrient loading, and the influence of periphyton grazers (the bladder snail, Physa fontinalis) of similar size and history were controlled. Plant growth and survival significantly increased in the presence of the periphyton grazer. Whilst the presence of the grazers had the largest influence on periphyton abundance, nutrient availability and plant type also had effects. Plant type had little influence on the nutritional quality of the periphyton measured as carbohydrate, protein and C:N. Effects of treatment on snail growth, and the timing and extent of snail reproduction disappeared when they were compared with the quantity of periphyton available. There was no evidence of enhanced grazer success in the presence of the live plants compared with inert substrata. Although submerged plants affect the growth and reproduction of the grazers which feed on their surfaces, through differences in the amount of periphyton which grows there, we found no evidence that they manipulate the periphyton to encourage such grazers. Received: 1 September 1998 / Accepted: 12 May 1999     

In vitro and in vivo evaluation of the antifungal activity of fluoxetine combined with antifungals against Candida albicans biofilms and oral candidiasis

Abstract

Candida albicans biofilms are responsible for oral candidiasis. Fluoxetine is a widely used antidepressant, with certain anti-Candida activities. The antifungal activity of fluoxetine combined with various antifungals against C. albicans biofilms and oral candidiasis was evaluated in this study. The morphological change in the inhibition of fluoxetine on C. albicans biofilms was observed using SEM. The interactions between fluoxetine and antifungals against C. albicans biofilms were evaluated using microdilution checkerboard methods, FICI and the ΔE model. The synergistic combination was tested in vivo on the mice model of oral candidiasis. SEM imaging showed fluoxetine inhibited hyphal growth and biofilm formation. Fluoxetine combined with caspofungin exhibited synergistic effects against C. albicans biofilms. Antagonistic effects occurred when fluoxetine was combined with amphotericin B or terbinafine. Further, the fluoxetine combined with caspofungin significantly reduced the lesion score and CFU of C. albicans on the murine tongue (p?<?0.05), and relieved oral candidiasis of the infected mice.     

Do rivers influence fine-scale population genetic structure of tigers in the Sundarbans?

Global tiger Panthera tigris populations mostly survive within the geographically fragmented forest patches, thereby limited genetic exchange between isolated populations. Assessing the genetic status of these populations can reveal the effects of dispersal barriers and provide critical insights to guide future conservation actions. Using non-invasively collected biological samples, we investigated fine-scale genetic structure of tigers in the Sundarbans mangrove forests intersected by the complex river systems, and which holds one of the largest global tiger populations. We genotyped 52 tiger samples at 10 polymorphic microsatellite loci, and sequenced 33 of them for a total of 1263 base-pairs at four mitochondrial gene fragments. Microsatellite analyses exhibit a signature of fine-scale genetic structure, which might have been the consequence of limited tiger dispersal due to wide rivers across the Sundarbans. Similarly, mitochondrial data show a historic pattern of population isolation that might be due to wider rivers across the entire Sundarbans shared by Bangladesh and India. Given the intrinsic nature of the mangrove habitat embedded with numerous rivers, increased commercial traffic and human activities may further impede tiger dispersal across wide rivers, escalating further genetic isolation of the Sundarbans tigers.     

Do copper ions influence the reduction of ferricytochrome C by O-2?

Recently, it was suggested that the measured rate of reduction of ferricytochrome C by O-2 below pH 8, was too high in the presence of high concentrations of formate (Koppenol, W.H., Van Buuren, K.J.H., Butler J. and Braams, R. (1976) Biochim. Biophys. Acta 449, 157-168). The high values were attributed to the presence of impurities of copper, which compete for O-2. This assumption is consistent with either a decrease in the reduction yield of ferricytochrome C in the presence of copper, or with a very fast reaction of Cu(I) with ferricytochrome C. It was previously shown by us and by others that the reduction yield of ferricytochrome C by O-2 IS 100%. We measured the rate of reduction of ferricytochrome C by Cu(I), and found that this reaction is slow: k = (1.5 +/- 0.5) . 10(3) M-1 . s-1. Therefore, our results rule out the possibility that below pH 8 copper impurities affect the measured rate constant of the reduction of ferricytochrome C by O-2.     

The influence of environmental factors on the rate and extent of stainless steel ennoblement mediated by manganese‐oxidizing biofilms

The increase in the open circuit potential of passive metals in natural waters due to biofilm formation at the metal surface, termed ennoblement, has been reported for nearly 30 years. Although its occurrence is undoubtedly associated with microbial colonization, the underlying mechanism of ennoblement remains controversial. Recent work produced in the authors’ laboratory has provided convincing experimental evidence that ennoblement can be caused by deposition of biomineralized manganese produced by manganese‐oxidizing biofilms. The purpose of this study was to determine the effects of environmental factors on the rate and extent of ennoblement of 316L stainless steel exposed to natural waters. This was accomplished by exposing corrosion coupons to four freshwater systems over a 4‐yearperiod. The rate and extent of ennoblement observed in these locations was correlated with dissolved manganese concentrations, the mass of accumulated manganese oxides, organic carbon concentration, dissolved oxygen concentration, flow, conditions, temperature, and pH in these environments.