Caterpillars and fungal pathogens: two co-occurring parasites of an ant-plant mutualism

In mutualisms, each interacting species obtains resources from its partner that it would obtain less efficiently if alone, and so derives a net fitness benefit. In exchange for shelter (domatia) and food, mutualistic plant-ants protect their host myrmecophytes from herbivores, encroaching vines and fungal pathogens. Although selective filters enable myrmecophytes to host those ant species most favorable to their fitness, some insects can by-pass these filters, exploiting the rewards supplied whilst providing nothing in return. This is the case in French Guiana for Cecropia obtusa (Cecropiaceae) as Pseudocabima guianalis caterpillars (Lepidoptera, Pyralidae) can colonize saplings before the installation of their mutualistic Azteca ants. The caterpillars shelter in the domatia and feed on food bodies (FBs) whose production increases as a result. They delay colonization by ants by weaving a silk shield above the youngest trichilium, where the FBs are produced, blocking access to them. This probable temporal priority effect also allows female moths to lay new eggs on trees that already shelter caterpillars, and so to occupy the niche longer and exploit Cecropia resources before colonization by ants. However, once incipient ant colonies are able to develop, they prevent further colonization by the caterpillars. Although no higher herbivory rates were noted, these caterpillars are ineffective in protecting their host trees from a pathogenic fungus, Fusarium moniliforme (Deuteromycetes), that develops on the trichilium in the absence of mutualistic ants. Therefore, the Cecropia treelets can be parasitized by two often overlooked species: the caterpillars that shelter in the domatia and feed on FBs, delaying colonization by mutualistic ants, and the fungal pathogen that develops on old trichilia. The cost of greater FB production plus the presence of the pathogenic fungus likely affect tree growth

Strategies of a parasite of the ant–Acacia mutualism

Mutualisms can be exploited by parasites—species that obtain resources from a partner but provide no services. Though the stability of mutualisms in the presence of such parasites is under intensive investigation, we have little information on life history traits that allow a species to be a successful mutualist or rather a parasite, particularly in cases where both are closely related. We studied the exploitation of Acacia myrmecophytes by the ant, Pseudomyrmex gracilis, contrasting with the mutualistic ant Pseudomyrmex ferrugineus. P. gracilis showed no host-defending behavior and had a negative effect on plant growth. By preventing the mutualist from colonization, P. gracilis imposes opportunity costs on the host plant. P. gracilis produced smaller colonies with a higher proportion of alates than did the mutualist and thus showed an “r-like” strategy. This appears to be possible because P. gracilis relies less on host-derived food resources than does the mutualist, as shown by behavioral and stable isotope studies. We discuss how this system allows the identification of strategies that characterize parasites of mutualisms

Unintended Consequences of Incentive Provision for Behaviour Change and Maintenance around Childbirth

Financial (positive or negative) and non-financial incentives or rewards are increasingly used in attempts to influence health behaviours. While unintended consequences of incentive provision are discussed in the literature, evidence syntheses did not identify any primary research with the aim of investigating unintended consequences of incentive interventions for lifestyle behaviour change. Our objective was to investigate perceived positive and negative unintended consequences of incentive provision for a shortlist of seven promising incentive strategies for smoking cessation in pregnancy and breastfeeding. A multi-disciplinary, mixed-methods approach included involving two service-user mother and baby groups from disadvantaged areas with experience of the target behaviours as study co-investigators. Systematic reviews informed the shortlist of incentive strategies. Qualitative semi-structured interviews and a web-based survey of health professionals asked open questions on positive and negative consequences of incentives. The participants from three UK regions were a diverse sample with and without direct experience of incentive interventions: 88 pregnant women/recent mothers/partners/family members; 53 service providers; 24 experts/decision makers and interactive discussions with 63 conference attendees. Maternity and early years health professionals (n = 497) including doctors, midwives, health visitors, public health and related staff participated in the survey. Qualitative analysis identified ethical, political, cultural, social and psychological implications of incentive delivery at population and individual levels. Four key themes emerged: how incentives can address or create inequalities; enhance or diminish intrinsic motivation and wellbeing; have a positive or negative effect on relationships with others within personal networks or health providers; and can impact on health systems and resources by raising awareness and directing service delivery, but may be detrimental to other health care areas. Financial incentives are controversial and generated emotive and oppositional responses. The planning, design and delivery of future incentive interventions should evaluate unexpected consequences to inform the evidence for effectiveness, cost-effectiveness and future implementation

Finality revived: powers and intentionality

Proponents of physical intentionality argue that the classic hallmarks of intentionality highlighted by Brentano are also found in purely physical powers. Critics worry that this idea is metaphysically obscure at best, and at worst leads to panpsychism or animism. I examine the debate in detail, finding both confusion and illumination in the physical intentionalist thesis. Analysing a number of the canonical features of intentionality, I show that they all point to one overarching phenomenon of which both the mental and the physical are kinds, namely finality. This is the finality of ‘final causes’, the long-discarded idea of universal action for an end to which recent proponents of physical intentionality are in fact pointing whether or not they realise it. I explain finality in terms of the concept of specific indifference, arguing that in the case of the mental, specific indifference is realised by the process of abstraction, which has no correlate in the case of physical powers. This analysis, I conclude, reveals both the strength and weakness of rational creatures such as us, as well as demystifying (albeit only partly) the way in which powers work

Formal modeling and analysis of cognitive agent behavior

From an external perspective, cognitive agent behavior can be described by specifying (temporal) correlations of a certain complexity between stimuli (input states) and (re)actions (output states) of the agent. From an internal perspective the agent’s dynamics can be characterized by direct (causal) temporal relations between internal and mental states of the agent. The latter type of specifications can be represented in a relatively simple, executable format, which enables different types of analysis of the agent’s behavior. In particular, simulations of the agent’s behavior under different (environmental) circumstances can be explored. Furthermore, by applying verification techniques, automated analysis of the consequences of the agent’s behavior can be carried out. To enable such types of analysis when only given an external behavioral specification, this has to be transformed first into some type of executable format. An automated procedure for such a transformation is proposed in this paper. The application of the transformation procedure is demonstrated for a number of cases, showing examples of the types of analysis as mentioned for different forms of behavior

Physics and Applications of Laser Diode Chaos

An overview of chaos in laser diodes is provided which surveys experimental achievements in the area and explains the theory behind the phenomenon. The fundamental physics underpinning this behaviour and also the opportunities for harnessing laser diode chaos for potential applications are discussed. The availability and ease of operation of laser diodes, in a wide range of configurations, make them a convenient test-bed for exploring basic aspects of nonlinear and chaotic dynamics. It also makes them attractive for practical tasks, such as chaos-based secure communications and random number generation. Avenues for future research and development of chaotic laser diodes are also identified.Comment: Published in Nature Photonic

Emission of Volatile Organic Compounds After Herbivory from Trifolium pratense (L.) Under Laboratory and Field Conditions

Plants emit a wide range of volatile organic compounds in response to damage by herbivores, and many of the compounds have been shown to attract the natural enemies of insect herbivores or serve for inter- and intra-plant communication. Most studies have focused on volatile emission in the laboratory while little is known about emission patterns in the field. We studied the emission of volatiles by Trifolium pratense (red clover) under both laboratory and field conditions. The emission of 24 compounds was quantified in the laboratory, of which eight showed increased emission rates after herbivory by Spodoptera littoralis caterpillars, including (E)-β-ocimene, the most abundant compound, (Z)-β-ocimene, linalool, (E)-β-caryophyllene, (E,E)-α-farnesene, 4,8-dimethyl-1,3,7-nonatriene (DMNT), 1-octen-3-ol, and methyl salicylate (MeSA). While most of these compounds have been reported as herbivore-induced volatiles from a wide range of plant taxa, 1-octen-3-ol seems to be a characteristic volatile of legumes. In the field, T. pratense plants with varying herbivore damage growing in established grassland communities emitted only 13 detectable compounds, and the correlation between herbivore damage and volatile release was more variable than in the laboratory. For example, the emission of (E)-β-ocimene, (Z)-β-ocimene, and DMNT actually declined with damage, while decanal exhibited increased emission with increasing herbivory. Elevated light and temperature increased the emission of many compounds, but the differences in light and temperature conditions between the laboratory and the field could not account for the differences in emission profiles. Our results indicate that the release of volatiles from T. pratense plants in the field is likely to be influenced by additional biotic and abiotic factors not measured in this study. The elucidation of these factors may be important in understanding the physiological and ecological functions of volatiles in plants

A Comparative Study of Human TLR 7/8 Stimulatory Trimer Compositions in Influenza A Viral Genomes

Background: Variation in the genomes of single-stranded RNA viruses affects their infectivity and pathogenicity in two ways. First, viral genome sequence variations lead to changes in viral protein sequences and activities. Second, viral genome sequence variation produces diversity at the level of nucleotide composition and diversity in the interactions between viral RNAs and host toll-like receptors (TLRs). A viral genome-typing method based on this type of diversity has not yet been established. Methodology/Principal Findings: In this study, we propose a novel genomic trait called the ‘‘TLR stimulatory trimer composition’ ’ (TSTC) and two quantitative indicators, Score S and Score N, named ‘‘TLR stimulatory scores’ ’ (TSS). Using the complete genome sequences of 10,994 influenza A viruses (IAV) and 251 influenza B viruses, we show that TSTC analysis reveals the diversity of Score S and Score N among the IAVs isolated from various hosts. In addition, we show that low values of Score S are correlated with high pathogenicity and pandemic potential in IAVs. Finally, we use Score S and Score N to construct a logistic regression model to recognize IAV strains that are highly pathogenic or have high pandemic potential. Conclusions/Significance: Results from the TSTC analysis indicate that there are large differences between human and avian IAV genomes (except for segment 3), as illustrated by Score S. Moreover, segments 1, 2, 3 and 4 may be majo

Young Aphids Avoid Erroneous Dropping when Evading Mammalian Herbivores by Combining Input from Two Sensory Modalities

Mammalian herbivores may incidentally ingest plant-dwelling insects while foraging. Adult pea aphids (Acyrthosiphon pisum) avoid this danger by dropping off their host plant after sensing the herbivore's warm and humid breath and the vibrations it causes while feeding. Aphid nymphs may also drop (to escape insect enemies), but because of their slow movement, have a lower chance of finding a new plant. We compared dropping rates of first-instar nymphs with those of adults, after exposing pea aphids to different combinations of simulated mammalian breath and vibrations. We hypothesized that nymphs would compensate for the greater risk they face on the ground by interpreting more conservatively the mammalian herbivore cues they perceive. Most adults dropped in response to breath alone, but nymphs rarely did so. Breath stimulus accompanied by one concurrent vibrational stimulus, caused a minor rise in adult dropping rates. Adding a second vibration during breath had no additional effect on adults. The nymphs, however, relied on a combination of the two types of stimuli, with a threefold increase in dropping rates when the breath was accompanied by one vibration, and a further doubling of dropping rates when the second vibration was added. The age-specificity of the aphids' herbivore detection mechanism is probably an adaptation to the different cost of dropping for the different age groups. Relying on a combination of stimuli from two sensory modalities enables the vulnerable nymphs to avoid costly mistakes. Our findings emphasize the importance of the direct trophic effect of mammalian herbivory for plant-dwelling insects

Oxidative stress augments toll-like receptor 8 mediated neutrophilic responses in healthy subjects

<p>Abstract</p> <p>Background</p> <p>Excessive oxidative stress has been reported to be generated in inflamed tissues and contribute to the pathogenesis of inflammatory lung diseases, exacerbations of which induced by viral infections are associated with toll-like receptor (TLR) activation. Among these receptors, TLR8 has been reported as a key receptor that recognizes single-strand RNA virus. However, it remains unknown whether TLR8 signaling is potentiated by oxidative stress. The aim of this study is to examine whether oxidative stress modulates TLR8 signaling in vitro.</p> <p>Methods</p> <p>Human peripheral blood neutrophils were obtained from healthy non-smokers and stimulated with TLR 7/8 agonist imidazoquinoline resiquimod (R848) in the presence or absence of hydrogen peroxide (H₂O₂). Neutrophilic responses including cytokine release, superoxide production and chemotaxis were examined, and the signal transduction was also analyzed.</p> <p>Results</p> <p>Activation of TLR8, but not TLR7, augmented IL-8 release. The R848-augmented IL-8 release was significantly potentiated by pretreatment with H₂O₂(p < 0.01), and N-acetyl-<smcaps>L</smcaps>-cysteine reversed this potentiation. The combination of H₂O₂and R848 significantly potentiated NF-kB phosphorylation and IkBα degradation. The H₂O₂-potentiated IL-8 release was suppressed by MG-132, a proteosome inhibitor, and by dexamethasone. The expressions of TLR8, myeloid differentiation primary response gene 88 (MyD88), and tumor necrosis factor receptor-associated factor 6 (TRAF6) were not affected by H₂O₂.</p> <p>Conclusion</p> <p>TLR8-mediated neutrophilic responses were markedly potentiated by oxidative stress, and the potentiation was mediated by enhanced NF-kB activation. These results suggest that oxidative stress might potentiate the neutrophilic inflammation during viral infection.</p