Differences in spontaneously avoiding or approaching mice reflect differences in CB1-mediated signaling of dorsal striatal transmission

Approach or avoidance behaviors are accompanied by perceptual vigilance for, affective reactivity to and behavioral predisposition towards rewarding or punitive stimuli, respectively. We detected three subpopulations of C57BL/6J mice that responded with avoiding, balancing or approaching behaviors not induced by any experimental manipulation but spontaneously displayed in an approach/avoidance conflict task. Although the detailed neuronal mechanisms underlying the balancing between approach and avoidance are not fully clarified, there is growing evidence that endocannabinoid system (ECS) plays a critical role in the control of these balancing actions. The sensitivity of dorsal striatal synapses to the activation of cannabinoid CB1 receptors was investigated in the subpopulations of spontaneously avoiding, balancing or approaching mice. Avoiding animals displayed decreased control of CB1 receptors on GABAergic striatal transmission and in parallel increase of behavioral inhibition. Conversely, approaching animals exhibited increased control of CB1 receptors and in parallel increase of explorative behavior. Balancing animals reacted with balanced responses between approach and avoidance patterns. Treating avoiding animals with URB597 (fatty acid amide hydrolase inhibitor) or approaching animals with AM251 (CB1 receptor inverse agonist) reverted their respective behavioral and electrophysiological patterns. Therefore, enhanced or reduced CB1-mediated control on dorsal striatal transmission represents the synaptic hallmark of the approach or avoidance behavior, respectively. Thus, the opposite spontaneous responses to conflicting stimuli are modulated by a different involvement of endocannabinoid signaling of dorsal striatal neurons in the range of temperamental traits related to individual differences.     

Survival of the feces: Does a nematode lungworm adaptively manipulate the behavior of its cane toad host?

Parasites can enhance their fitness by modifying the behavior of their hosts in ways that increase rates of production and transmission of parasite larvae. We used an antihelminthic drug to experimentally alter infections of lungworms (Rhabdias pseudosphaerocephala) in cane toads (Rhinella marina). We then compared subsequent behaviors of dewormed toads versus toads that retained infections. Both in the laboratory and in the field, the presence of parasites induced hosts to select higher body temperatures (thereby increasing rates of lungworm egg production), to defecate in moister sites, and to produce feces with higher moisture content (thereby enhancing survival of larvae shed in feces). Because those behavioral modifications enhance rather than decrease parasite fitness, they are likely to have arisen as adaptive manipulations of host behavior rather than as host adaptations to combat infection or as nonadaptive consequences of infection on host physiology. However, the mechanisms by which lungworms alter cane toad thermal preference and defecation are not known. Although many examples of host manipulation by parasites involve intermediate hosts facilitating their own demise, our findings indicate that manipulation of definitive hosts can be as subtle as when and where to defecate.     

Genetic variation in resistance, but not tolerance, to a protozoan parasite in the monarch butterfly

Natural selection should strongly favour hosts that can protect themselves against parasites. Most studies on animals so far have focused on resistance, a series of mechanisms through which hosts prevent infection, reduce parasite growth or clear infection. However, animals may instead evolve tolerance, a defence mechanism by which hosts do not reduce parasite infection or growth, but instead alleviate the negative fitness consequences of such infection and growth. Here, we studied genetic variation in resistance and tolerance in the monarch butterfly (Danaus plexippus) to its naturally occurring protozoan parasite, Ophryocystis elektroscirrha. We exposed 560 monarch larvae of 19 different family lines to one of five different parasite inoculation doses (0, 1, 5, 10 and 100 infective spores) to create a range of parasite loads in infected butterflies. We then used two proxies of host fitness (adult lifespan and body mass) to quantify: (i) qualitative resistance (the ability to prevent infection; also known as avoidance or anti-infection resistance); (ii) quantitative resistance (the ability to limit parasite growth upon infection; also known as control or anti-growth resistance); and (iii) tolerance (the ability to maintain fitness with increasing parasite infection intensity). We found significant differences among host families in qualitative and quantitative resistance, indicating genetic variation in resistance. However, we found no genetic variation in tolerance. This may indicate that all butterflies in our studied population have evolved maximum tolerance, as predicted by some theoretical models.     

Avenues of the membrane transport system in adaptation of plants to abiotic stresses

Abstract

Abiotic stress imposed by many factors such as: extreme water regimes, adverse temperatures, salinity, and heavy metal contamination result in severe crop yield losses worldwide. Plants must be able to quickly respond to these stresses in order to adapt to their growing conditions and minimize metabolic losses. In this context, transporter proteins play a vital role in regulating stress response mechanisms by facilitating movement of a variety of molecules and ions across the plasma membrane in order to maintain fundamental cellular processes such as ion homeostasis, osmotic adjustment, signal transduction, and detoxification. Aquaporins play a crucial role in alleviating abiotic stress by transporting water and other small molecules to maintain cellular homeostasis. Similarly, other transporter families such as CDF, ZIP, ABC, NHX, HKT, SWEETs, TMTs, and ion channels also contribute to abiotic stress tolerance. Hormones and other signaling molecules are necessary to coordinate responses across different tissues and to precisely regulate molecular trafficking. The present review highlights the current understanding of how membrane transporters orchestrate stress responses in plants. It also provides insights about the importance of these sensing and adaptive mechanisms for ensuring improved sustainable crop production during unfavorable conditions. Finally, this review discusses future prospects for the use of computational tools in constructing signaling networks to improve our understanding of the behavior of transporters under abiotic stress.     

动物个性研究进展

"个性"是指不同时空条件下动物种群个体间行为的稳定差异。大量的理论和实验性研究表明,个性差异在动物界普遍存在,其是种群多度和分布、物种共存及群落构建的重要驱动因子。介绍了动物个性的概念、分类及衡量指标,将前人测量个性类型的方法加以总结;随后介绍了动物个性的生态学意义,尤其是个性对动物生活史策略、种群分布与多度、群落结构和动态、生态系统功能和过程以及疾病与信息传播等的影响。在此基础上,进一步分析了在人类活动增加等全球变化背景下,动物个性如何调控动物个体行为、种群和群落动态对这些环境变化的响应。阐述了动物个性的形成与维持机制,并对未来的研究方向进行了展望。     

Does animal behavior underlie covariation between hosts' exposure to infectious agents and susceptibility to infection? Implications for disease dynamics

Animal behavior is unique in influencing both components of the process of transmission of disease: exposure to infectious agents, and susceptibility to infection once exposed. To date, the influence of behavior on exposure versus susceptibility has largely been considered separately. Here, we ask whether these two key mechanisms act in concert in natural populations, whereby individuals who are most exposed to infectious agents or have the most contact with conspecifics are also the most susceptible or infectious. We propose three mechanisms that can generate covariation between these two key elements of the transmission of disease within and among hosts, and we provide empirical examples of each. We then use a mathematical model to examine the effect of this covariation on the dynamics of disease at the population level. First, we show that the empirical mechanisms generating covariation between behavioral and physiological components of disease transmission are widespread and include endocrine mediators of behavior, mate choice, group size, sickness behaviors, and behavioral avoidance of infectious conspecifics. The diversity of these empirical mechanisms underscores the potential importance and breadth of covariation in the disease process. Second, we show mathematically that the variability in hosts' exposure to infectious agents and susceptibility or infectiousness, and how tightly they are coupled, strongly influences the ability of a disease to invade a host population. Overall, we propose that covariation between behavioral and physiological components of transmission is likely widespread in natural populations, and can have important consequences for the dynamics of disease at the population level as well as for our understanding of sexual selection, social behavior, and animal communication.     

The economy of inflammation: when is less more?

In ecology, tolerance of parasites refers to host mitigation of the fitness costs of an infection. This concept of parasite tolerance contrasts with resistance, whereby hosts reduce the intensity of an infection. Anti-inflammatory cells and molecules have been implicated as mechanisms of parasite tolerance, suggesting that a major role of tolerance is in minimizing collateral damage associated with inflammation. A framework is proposed here in which the cost-benefit outcome of an inflammatory host-response is hypothesized to be dependent on host life-history, parasite virulence, and the efficacy of a current inflammatory or anti-inflammatory response. Testable predictions, both within and among host species, are presented for this hypothesis.     

A mutation in CLOCK leads to altered dopamine receptor function

Mice with a mutation in the Clock gene (ClockΔ19) have a number of behavioral phenotypes that suggest alterations in dopaminergic transmission. These include hyperactivity, increased exploratory behavior, and increased reward value for drugs of abuse. However, the complex changes in dopaminergic transmission that underlie the behavioral abnormalities in these mice remain unclear. Here we find that a loss of CLOCK function increases dopamine release and turnover in striatum as indicated by increased levels of metabolites HVA and DOPAC, and enhances sensitivity to dopamine receptor antagonists. Interestingly, this enlarged dopaminergic tone results in downstream changes in dopamine receptor (DR) levels with a surprising augmentation of both D1‐ and D2‐type DR protein, but a significant shift in the ratio of D1 : D2 receptors in favor of D2 receptor signaling. These effects have functional consequences for both behavior and intracellular signaling, with alterations in locomotor responses to both D1‐type and D2‐type specific agonists and a blunted response to cAMP activation in the ClockΔ19 mutants. Taken together, these studies further elucidate the abnormalities in dopaminergic transmission that underlie mood, activity, and addictive behaviors.     

Stereotypies and other abnormal repetitive behaviors: potential impact on validity, reliability, and replicability of scientific outcomes

Normal behavior plays a key role in facilitating homeostasis, especially by allowing the animal to control and modify its environment. Captive environments may interfere with these behavioral responses, and the resulting stress may alter many physiological parameters. Abnormal behaviors indicate that an animal is unable to adjust behaviorally to the captive environment and, hence, may be expressing abnormal physiology. Therefore, captive environments may affect the following aspects of an experiment: validity, by introducing abnormal animals into experiments; reliability, by increasing interindividual variation through the introduction of such individuals; and replicability, by altering the number and type of such individuals between laboratories. Thus, far from increasing variability, enrichment may actually improve validity, reliability, and replicability by reducing the number of abnormal animals introduced into experiments. In this article, the specific example of abnormal repetitive behaviors (ARBs) is explored. ARBs in captive animals appear to involve the same mechanisms as ARBs in human psychiatry, which reflect underlying abnormalities of brain function. ARBs are also correlated with a wide range of behavioral changes that affect experimental outcomes. Thus, ARBs in laboratory animals may compromise validity, reliability, and replicability, especially in behavioral experiments; and enrichments that prevent ARB may enhance validity, reliability, and replicability. Although many links in this argument have been tested experimentally, key issues still remain in the interpretation of these data. In particular, it is currently unclear (1) whether or not the differences in brain function seen in animals performing ARB are abnormal, (2) which common behavioral paradigms are affected by ARB, and (3) whether enrichment does indeed improve the quality of behavioral data. Ongoing and future work addressing these issues is outlined.     

Behavioral and physiological female responses to male sex ratio bias in a pond-breeding amphibian

Introduction

The phenomenon of sexual conflict has been well documented, and in populations with biased operational sex ratios the consequences for the rarer sex can be severe. Females are typically a limited resource and males often evolve aggressive mating behaviors, which can improve individual fitness for the male while negatively impacting female condition and fitness. In response, females can adjust their behavior to minimize exposure to aggressive mating tactics or minimize the costs of mating harassment. While male-male competition is common in amphibian mating systems, little is known about the consequences or responses of females. The red-spotted newt (Notophthalmus viridescens) is a common pond-breeding amphibian with a complex, well-studied mating system where males aggressively court females. Breeding populations across much of its range have male-biased sex ratios and we predicted that female newts would have behavioral mechanisms to mitigate mating pressure from males. We conducted four experiments examining the costs and behavioral responses of female N. viridescens exposed to a male-biased environment.

Results

In field enclosures, we found that female newts exposed to a male-biased environment during the five-month breeding season ended with lower body condition compared to those in a female-biased environment. Shorter-term exposure to a male-biased environment for five weeks caused a decrease in circulating total leukocyte and lymphocyte abundance in blood, which suggests females experienced physiological stress. In behavioral experiments, we found that females were more agitated in the presence of male chemical cues and females in a male-biased environment spent more time in refuge than those in a female-biased environment.

Conclusions

Our results indicate that male-biased conditions can incur costs to females of decreased condition and potentially increased risk of infection. However, we found that females can also alter their behavior and microhabitat use under a male-biased sex ratio. Consistent with surveys showing reduced detection probabilities for females, our research suggests that females avoid male encounters using edge and substrate habitat. Our work illustrates the integrated suite of impacts that sexual conflict can have on the structure and ecology of a population.     

昆虫病原微生物对其寄主行为的调控作用研究进展

昆虫病原微生物是调控昆虫种群数量动态的重要因子,其作为生物防治害虫的重要手段被广泛应用。昆虫病原物往往通过调控其寄主行为来提高自身的适应性,而有些寄主行为的改变却是其应对病原物侵染的免疫反应。发烧行为被证明可抑制病原增殖并延长寄主死亡;取食行为变化影响病原物或寄主的适应性;繁殖行为主要表现在产卵力、交配行为和性信息素等方面的变化;社会性行为改变对整个社会群体的适应性或病原物传播有影响;病原物所引起的寄主防卫和群集能力下降被认为对病原传播不利;病虫趋光和趋地行为、顶峰行为和活体寄主传病行为等被认为是病原物操纵的有利于病原微生物扩散和传播的行为。明确昆虫病原物调控其寄主行为的策略和机制对于寻找到新的害虫防治方法有指导意义。     

Genotype and diet affect resistance,survival, and fecundity but not fecundity tolerance

Insects are exposed to a variety of potential pathogens in their environment, many of which can severely impact fitness and health. Consequently, hosts have evolved resistance and tolerance strategies to suppress or cope with infections. Hosts utilizing resistance improve fitness by clearing or reducing pathogen loads, and hosts utilizing tolerance reduce harmful fitness effects per pathogen load. To understand variation in, and selective pressures on, resistance and tolerance, we asked to what degree they are shaped by host genetic background, whether plasticity in these responses depends upon dietary environment, and whether there are interactions between these two factors. Females from ten wild‐type Drosophila melanogaster genotypes were kept on high‐ or low‐protein (yeast) diets and infected with one of two opportunistic bacterial pathogens, Lactococcus lactis or Pseudomonas entomophila. We measured host resistance as the inverse of bacterial load in the early infection phase. The relationship (slope) between fly fecundity and individual‐level bacteria load provided our fecundity tolerance measure. Genotype and dietary yeast determined host fecundity and strongly affected survival after infection with pathogenic P. entomophila. There was considerable genetic variation in host resistance, a commonly found phenomenon resulting from for example varying resistance costs or frequency‐dependent selection. Despite this variation and the reproductive cost of higher P. entomophila loads, fecundity tolerance did not vary across genotypes. The absence of genetic variation in tolerance may suggest that at this early infection stage, fecundity tolerance is fixed or that any evolved tolerance mechanisms are not expressed under these infection conditions.     

Beyond immunity: quantifying the effects of host anti-parasite behavior on parasite transmission

A host’s first line of defense in response to the threat of parasitic infection is behavior, yet the efficacy of anti-parasite behaviors in reducing infection are rarely quantified relative to immunological defense mechanisms. Larval amphibians developing in aquatic habitats are at risk of infection from a diverse assemblage of pathogens, some of which cause substantial morbidity and mortality, suggesting that behavioral avoidance and resistance could be significant defensive strategies. To quantify the importance of anti-parasite behaviors in reducing infection, we exposed larval Pacific chorus frogs (Pseudacris regilla) to pathogenic trematodes (Ribeiroia and Echinostoma) in one of two experimental conditions: behaviorally active (unmanipulated) or behaviorally impaired (anesthetized). By quantifying both the number of successful and unsuccessful parasites, we show that host behavior reduces infection prevalence and intensity for both parasites. Anesthetized hosts were 20–39% more likely to become infected and, when infected, supported 2.8-fold more parasitic cysts. Echinostoma had a 60% lower infection success relative to the more deadly Ribeiroia and was also more vulnerable to behaviorally mediated reductions in transmission. For Ribeiroia, increases in host mass enhanced infection success, consistent with epidemiological theory, but this relationship was eroded among active hosts. Our results underscore the importance of host behavior in mitigating disease risk and suggest that, in some systems, anti-parasite behaviors can be as or more effective than immune-mediated defenses in reducing infection. Considering the severe pathologies induced by these and other pathogens of amphibians, we emphasize the value of a broader understanding of anti-parasite behaviors and how co-occurring stressors affect them.     

Historical and ecological controls on phylogenetic diversity in Californian plant communities

An unresolved controversy regarding social behaviors is exemplified when natural selection might lead to behaviors that maximize fitness at the social-group level but are costly at the individual level. Except for the special case of groups of clones, we do not have a general understanding of how and when group-optimal behaviors evolve, especially when the behaviors in question are flexible. To address this question, we develop a general model that integrates behavioral plasticity in social interactions with the action of natural selection in structured populations. We find that group-optimal behaviors can evolve, even without clonal groups, if individuals exhibit appropriate behavioral responses to each other's actions. The evolution of such behavioral responses, in turn, is predicated on the nature of the proximate behavioral mechanisms. We model a particular class of proximate mechanisms, prosocial preferences, and find that such preferences evolve to sustain maximum group benefit under certain levels of relatedness and certain ecological conditions. Thus, our model demonstrates the fundamental interplay between behavioral responses and relatedness in determining the course of social evolution. We also highlight the crucial role of proximate mechanisms such as prosocial preferences in the evolution of behavioral responses and in facilitating evolutionary transitions in individuality.     

Environmental dependency in the expression of costs of tolerance to deer herbivory

Plant tolerance to natural enemy damage is a defense strategy that minimizes the effects of damage on fitness. Despite the apparent benefits of tolerance, many populations exhibit intermediate levels of tolerance, indicating that constraints on the evolution of tolerance are likely. In a field experiment with the ivyleaf morning glory, costs of tolerance to deer herbivory in the form of negative genetic correlations between deer tolerance and fitness in the absence of damage were detected. However, these costs were detected only in the presence of insect herbivores. Such environmental dependency in the expression of costs of tolerance may facilitate the maintenance of tolerance at intermediate levels.     

Bigger groups have fewer parasites and similar cortisol levels: a multi-group analysis in red colobus monkeys

If stress and disease impose fitness costs, and if those costs vary as a function of group size, then stress and disease should exert selection pressures on group size. We assessed the relationships between group size, stress, and parasite infections across nine groups of red colobus monkeys (Procolobus rufomitratus) in Kibale National Park, Uganda. We used fecal cortisol as a measure of physiological stress and examined fecal samples to assess the prevalence and intensity of gastrointestinal helminth infections. We also examined the effect of behaviors that could potentially reduce parasite transmission (e.g., increasing group spread and reducing social interactions). We found that cortisol was not significantly related to group size, but parasite prevalence was negatively related to group size and group spread. The observed increase in group spread could have reduced the rate of parasite transmission in larger groups; however, it is not clear whether this was a density-dependent behavioral counter-strategy to infection or a response to food competition that also reduced parasite transmission. The results do not support the suggestion that gastrointestinal parasitism or stress directly imposed group-size-related fitness costs, and we cannot conclude that they are among the mechanisms limiting group size in red colobus monkeys.     

Neuroimmune mechanisms in fetal alcohol spectrum disorder

Fetal alcohol spectrum disorder (FASD) is a major health concern worldwide and results from maternal consumption of alcohol during pregnancy. It produces tremendous individual, social, and economic losses. This review will first summarize the structural, functional, and behavior changes seen in FASD. The development of the neuroimmune system will be then be described with particular emphasis on the role of microglial cells in the normal regulation of homeostatic function in the central nervous system (CNS) including synaptic transmission. The impact of alcohol on the neuroimmune system in the developing CNS will be discussed in the context of several key immune molecules and signaling pathways involved in neuroimmune mechanisms that contribute to FASD. This review concludes with a summary of the development of early therapeutic approaches utilizing immunosuppressive drugs to target alcohol-induced pathologies. The significant role played by neuroimmune mechanisms in alcohol addiction and pathology provides a focus for future research aimed at understanding and treating the consequences of FASD. ? 2012 Wiley Periodicals, Inc. Develop Neurobiol, 2012.