The Effect of Chemical Information on the Spatial Distribution of Fruit Flies: I Model Results

Animal aggregation is a general phenomenon in ecological systems. Aggregations are generally considered as an evolutionary advantageous state in which members derive the benefits of protection and mate choice, balanced by the costs of limiting resources and competition. In insects, chemical information conveyance plays an important role in finding conspecifics and forming aggregations. In this study, we describe a spatio-temporal simulation model designed to explore and quantify the effects of these infochemicals, i.e., food odors and an aggregation pheromone, on the spatial distribution of a fruit fly (Drosophila melanogaster) population, where the lower and upper limit of local population size are controlled by an Allee effect and competition. We found that during the spatial expansion and strong growth of the population, the use of infochemicals had a positive effect on population size. The positive effects of reduced mortality at low population numbers outweighed the negative effects of increased mortality due to competition. At low resource densities, attraction toward infochemicals also had a positive effect on population size during recolonization of an area after a local population crash, by decreasing the mortality due to the Allee effect. However, when the whole area was colonized and the population was large, the negative effects of competition on population size were larger than the positive effects of the reduction in mortality due to the Allee effect. The use of infochemicals thus has mainly positive effects on population size and population persistence when the population is small and during the colonization of an area. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users.     

棉铃虫对几种信息化合物的触角电位 (EAG)反应

通过棉铃虫成虫对 1 0种寄主植物挥发性物质、两种性信息素组分及两者的混合作用的触角电位反应 ( EAG) ,发现棉铃虫雌雄蛾对 1 0种挥发性物质的 EAG反应差异显著 ( P<0 .0 5 ) ,说明了 1 0种挥发物质对棉铃虫成虫的感应功能有所不同。 1 0种寄主植物挥发物质与性信息素主要组分混合后能引起雄蛾 EAG反应明显高于单独性信息素的反应 ,其中有 4种挥发性物质明显地增强棉铃虫对性信息素的反应 ( P<0 .0 5 ) ,即庚醛、1 -己醇、反 - 2 -己烯醇、顺 - 3-己醇 - 1 ,说明了以寄主植物挥发物质与昆虫性信息素混合作用来增强昆虫性信息素的应用效果。不同光温条件下饲养的雄蛾对寄主植物挥发性物质与性信息素相互作用的 EAG反应差异显著 ( P<0 .0 5 )。     

信息化合物对昆虫行为的影响

本文综述了来自寄主植物的挥发性物质和同种昆虫或异种昆虫释放的各种信息素及两者的协同作用的信息化合物对昆虫行为的影响。特别强调了寄主植物的气味物质和昆虫信息素协同作用在昆虫寻找寄主、求偶、交配及天敌在寄主识别过程中的重要地位。昆虫对寄主植物的识别是由于识别了植物气味的由一定组分、按照严格比例组成的化学指纹图。昆虫信息素与植物挥发性物质相结合为昆虫寻找求偶、交配场所提供更复杂或更全面的信息。许多昆虫只有在寄主植物或寄主植物气味存在时 ,才能释放性或聚集信息素。天敌在寄主识别、搜索及定位等一系列过程中 ,来自寄主的食料、寄主本身及两者的互作的信息化合物起重要的作用。研究信息化合物对昆虫行为的影响可以探索昆虫各种行为的内在机理 ,更好的了解寄主—昆虫—天敌三层营养关系的相互作用 ,对利用天然活性化合物防治害虫及生物防治提供理论依据     

风洞技术

风洞技术是测定信息化学物质对昆虫行为影响研究中非常重要的实验手段,可为确定信息物质的浓度、配比提供参考,也可辅助诱芯的改进和诱捕器的设计。实际上风洞实验是一种信息物质田间应用前的室内模拟测试。风洞实验前要做好充分的准备,观察和记录的指标因测试的是性信息素还是植物挥发物而不同。本文重点介绍了风洞实验的具体操作步骤,列举了风洞技术在苹果蠹蛾Cydia pomonella多成分性信息素研究和葡萄藤蛾Lobesia botrana对葡萄主要挥发物的行为反应研究中的两个应用实例,最后还讨论了风洞与嗅觉仪的区别、风洞的优缺点,以及风洞的日常维护等。     

Plant-food and tool transfer among savanna chimpanzees at Fongoli, Senegal

Transferring food is considered a defining characteristic of humans, as such behavior is relatively uncommon in other animal species save for kin-based transfer. Chimpanzees (Pan troglodytes) are one exception, as they commonly transfer meat among nonrelatives but rarely transfer other resources. New observations at Fongoli, Senegal, show habitual transfer of wild-plant foods and other non-meat resources among community members beyond transfers from mother to offspring. We explore various explanations for these behaviors with a focus on age- and sex-class patterns in transfer events. In a total of 27 of 41 cases, male chimpanzees at Fongoli transferred wild-plant foods or tools to females. Most other cases involved transfer among males or males taking food from females. In light of male–female transfer patterns at Fongoli, we examine four hypotheses that have been applied to food transfer in apes: (1) testing for male-coercive tendency (van Noordwijk and van Schaik, Behav Ecol Sociobiol 63:883–890, 2009), (2) costly signaling (Hockings et al. PLoS ONE 2:e886, 2007), (3) food-for-sex (Gomes and Boesch, PLoS ONE 4:5116, 2009), and (4) sharing-under-pressure (Gilby, Anim Behav 71:953–963, 2006). We also consider hypotheses posed to explain transfer among callitrichids, where such behavior is more common (Ruiz-Miranda et al. Am J Primatol 48:305–320, 1999). Finally, we examine variables such as patch and food size and food transport. We discuss our findings relative to general patterns of non-meat transfer in Pan and examine them in the context of chimpanzee sociality in particular. We then contrast chimpanzee species and subspecies in terms of non-meat food and tool transfer and address the possibility that a savanna environment contributes to the unusual pattern observed at Fongoli.     

Representation of a mixture of pheromone and host plant odor by antennal lobe projection neurons of the silkmoth Bombyx mori

Pheromone-source orientation behavior can be modified by coexisting plant volatiles. Some host plant volatiles enhance the pheromonal responses of olfactory receptor neurons and increase the sensitivity of orientation behavior in the Lepidoptera species. Although many electrophysiological studies have focused on the pheromonal response of olfactory interneurons, the response to the mixture of pheromone and plant odor is not yet known. Using the silkmoth, Bombyx mori, we investigated the physiology of interneurons in the antennal lobe (AL), the primary olfactory center in the insect brain, in response to a mixture of the primary pheromone component bombykol and cis-3-hexen-1-ol, a mulberry leaf volatile. Application of the mixture enhanced the pheromonal responses of projection neurons innervating the macroglomerular complex in the AL. In contrast, the mixture of pheromone and cis-3-hexen-1-ol had little influence on the responses of projection neurons innervating the ordinary glomeruli whereas other plant odors dynamically modified the response. Together this suggests moths can process plant odor information under conditions of simultaneous exposure to sex pheromone.     

Dietary specialization and infochemical use in carnivorous arthropods: testing a concept

For the location of hosts and prey, insect carnivores (i.e., parasitoids or predators) often use infochemical cues that may originate from the host/prey itself but also from the food of the host/prey, a food plant, or another feeding substrate. These cues can be either specific for certain host/prey complexes or generally present in various complexes, and the reaction of the carnivores to these cues is either innate or learned. According to the concept on dietary specialization and infochemical use in natural enemies, the origin and specificity of the infochemical cues used and the innateness of the behavioural response are dependent on the degree of dietary specialization of the carnivore and its host/prey species. This concept has been widely adopted and has been frequently cited since its publication. Only few studies, however, have been explicitly designed to test predictions of the concept. Thus, more than 10 years after publication and despite of its broad acceptance, the general validity of the concept is still unclear. Using data from about 140 research papers on 95 species of parasitoids and predators, the present literature study comparatively scrutinises predictions from the concept. In accordance with the concept, learning to react to infochemicals and the use of general host and host plant cues was more often found in generalists than in specialists. In addition, more specialists were using specific infochemicals than generalists. In contrast to the concept, however, there was no significant difference between specialists and generalists in the proportion of carnivore species that use infochemicals during foraging and also extreme generalists are using infochemical cues for foraging. Likewise, an innate reaction to infochemicals was found in both specialists and generalists. Several reasons why infochemical use, including an innate reaction to infochemicals, is adaptive in generalist carnivores are discussed . We conclude that the concept has been a useful paradigm in advancing the chemical ecology of arthropod carnivores, but needs to be modified: the use of infochemicals is expected in all arthropod carnivores, regardless of dietary specialization.     

Oscillation and coding in a formal neural network considered as a guide for plausible simulations of the insect olfactory system

For the analysis of coding mechanisms in the insect olfactory system, a fully connected network of synchronously updated McCulloch and Pitts neurons (MC-P type) was developed [Quenet, B., Horn, D., 2003. The dynamic neural filter: a binary model of spatio-temporal coding. Neural Comput. 15 (2), 309-329]. Considering the update time as an intrinsic clock, this "Dynamic Neural Filter" (DNF), which maps regions of input space into spatio-temporal sequences of neuronal activity, is able to produce exact binary codes extracted from the synchronized activities recorded at the level of projection neurons (PN) in the locust antennal lobe (AL) in response to different odors [Wehr, M., Laurent, G., 1996. Odor encoding by temporal sequences of firing in oscillating neural assemblies. Nature 384, 162-166]. Here, in a first step, we separate the populations of PN and local inhibitory neurons (LN) and use the DNF as a guide for simulations based on biological plausible neurons (Hodgkin-Huxley: H-H type). We show that a parsimonious network of 10 H-H neurons generates action potentials whose timing represents the required codes. In a second step, we construct a new type of DNF in order to study the population dynamics when different delays are taken into account. We find synaptic matrices which lead to both the emergence of robust oscillations and spatio-temporal patterns, using a formal criterion, based on a Normalized Euclidian Distance (NED), in order to measure the use of the temporal dimension as a coding dimension by the DNF. Similarly to biological PN, the activity of excitatory neurons in the model can be both phase-locked to different cycles of oscillations which remind local field potential (LFP), and nevertheless exhibit dynamic behavior complex enough to be the basis of spatio-temporal codes.     

Role of infochemical mediated zooplankton grazing in a phytoplankton competition model

Infochemicals released by marine phytoplankton play important roles in food web interactions by influencing the feeding behavior and selectivity of zooplanktonic predators. Recent modeling efforts have focused on the role of such chemicals as toxic grazing deterrents in phytoplankton competition. However, infochemicals may also be utilized as grazing cues, leading predators to profitable foraging patches. Here we investigate the role of infochemical mediated zooplankton grazing in a standard 3-species phytoplankton competition model, with the aim of further elucidating the ecological role of phytoplankton derived infochemicals. We then extend this to consider a more realistic 4-species model. The models produce a range of solutions depending on the strength of competition and microzooplankton grazing selectivity. Our key result is that infochemical chemoattractants, which increase the susceptibility of the producer to grazing, can provide a refuge for both competing phytoplankton species by attracting carnivorous copepods to consume microzooplankton grazers in a multi-trophic interaction. Our results indicate that infochemicals potentially have important consequences for the dynamics of marine food webs.     

Gastropod grazing on a benthic alga leads to liberation of food‐finding infochemicals

Chemical information transfer is a major agent in the regulation of interspecific and intraspecific interactions in natural ecosystems. One important group of such infochemicals both in terrestrial and aquatic ecosystems are so‐called volatile organic compounds (VOCs) that can evoke behavioral or physiological responses like predator avoidance and mate or host location. In previous work, we have demonstrated that freshwater gastropods utilize VOCs released from benthic algae as food finding cues, although the specific nature of the VOC release and perception were not yet clear. Therefore we tested whether gastropod grazing on biofilms leads to algal cell damage and a subsequent liberation of wounding‐associated VOCs. In bioassays we investigated the algal VOC bouquet level which is necessary to elicit a behavioural response of freshwater gastropods. The results of the liberation experiment showed that gastropod grazing leads to VOCs release. We also found that a certain threshold level of volatiles is necessary for snails to recognise the volatile infochemicals and subsequently respond with a directed foraging behaviour towards the odour. Finally, a calculated mass balance model demonstrated that the grazer mediated VOC release produced a signal concentration that is sufficient to be recognized by conspecifics and utilized as foraging infochemicals. The emission of ecologically relevant volatiles through snail grazing with subsequent attraction of other gastropod grazers to algal biofilms indicates an important but so far understudied chemical signaling mechanism of ecological importance.     

Visual cue learning and odometry in guiding the search behavior of desert ants, Melophorus bagoti, in artificial channels

Terrestrial panoramic cues, path integration and search behavior are the main navigational strategies used by ants to locate food and find their way back to the nest. Searching becomes important when the other navigational cues are either not available or cannot provide sufficient information to pinpoint the goal. When searching in one-dimensional channels Melophorus bagoti ants exhibit a systematic drift in the starting-point-to-goal direction as they turn back and forth, sometimes past the goal location ( Narendra et al., 2008). Here we show that this drift in channels is not a stereotypical part of the search behavior in these ants. It rather depends on the conditions of training. In experiments in which the nest entrance is located not at the end but at the side of the channel, forward drift is not always part of the nest search. Experiments on food searches showed that with the food source at the end of the channel, ants performed a linear drift in the starting-point-to-food direction. With food at the side of the channel, they showed a less pronounced drift toward the food source. In this constrained environment, especially with the goal at the end of the channel, ants seem to learn a routine such as ‘run along the channel’, and mix this routine with their usual strategy of turning back and forth in search.     

Molecular and functional characterization of an odorant binding protein of the Asian elephant,Elephas maximus: implications for the role of lipocalins in mammalian olfaction

The sex pheromone present in the pre-ovulatory urine of female Asian elephants is the simple lipid (Z)-7-dodecen-1-yl acetate (Z7-12:Ac). Using radiolabeled probes, we have identified a pheromone binding protein that is abundant in the mucus of the trunk; this protein is homologous to a class of lipocalins known as odorant binding proteins (OBPs). To test five previously proposed roles for the OBP in chemosensory perception, we determined the equilibrium dissociation constant of the OBP-pheromone complex, as well as the association and dissociation rates. Using a mathematical model in conjunction with experimental data, we suggest that the binding and release of the pheromone by the OBP are too slow for the OBP to function in transporting the pheromone through the mucus that covers the olfactory sensory epithelium. Our data indicate that the elephant OBP only modestly increases the solubility of the pheromone in the mucus. Our results are most consistent with the notion that elephant OBP functions as a scavenger of the pheromone and possibly other ligands, including odorants. In light of these findings, and published results for other mammalian OBP-ligand complexes, a general model for the role of OBPs in mammalian olfaction is proposed. Moreover, the potential implications of these findings for interaction of Z7-12:Ac with insect antennal proteins are discussed.     

Asymmetry and Dimensions of Relationship Quality in the Japanese Macaque (<Emphasis Type="Italic">Macaca fuscata yakui</Emphasis>)

Cords and Aureli (2000) proposed that relationship quality can be described by three components, i.e., value, security, and compatibility, based on the benefits social partners receive from their relationship and on how likely it is for them to maintain a stable friendly relationship over time. We aimed to examine whether this 3-components structure can describe social relationships and to investigate the degree of asymmetry of social relationships. We used the Japanese macaque as our model species, as group members may form strong social relationships with one another. We collected 359.2 h of focal samples, on 21 monkeys, and ran a principal component analysis (PCA) on dyadic scores for 9 variables measuring social relationships, e.g., grooming or aggression. This PCA gave 3 components. However, a second PCA run on scores per individual, i.e. for each variable and dyad we obtained 1 score for the actor and 1 for the receiver of behavior, gave a 5-component structure. We interpreted this result as evidence of the asymmetric nature of social relationships, in terms of the frequency and type of behavior exchanged between social partners, in the Japanese macaque. This interpretation was confirmed by the low correlation coefficients between behaviors given and received within a dyad. Overall these results provide mixed support for the 3-components structure predicted by Cords and Aureli (2000). They also show that social relationships may be largely asymmetric and that this asymmetry should be considered in studies on social behavior.     

水稻挥发性信息化合物对昆虫的作用

植物挥发性化合物是联系植物、害虫和天敌间3层营养关系的关键信息因子。是害虫防治理论与实践的基础．首先,介绍了水稻挥发性信息化合物的基本化学特征及其在植食性昆虫和天敌昆虫寄主选择中的作用;其次,分析了水稻挥发性信息化合物的产生与作用机制及其生态学功能和水稻挥发性信息化合物研究中存在的问题;最后,展望了水稻挥发性信息化合物的研究前景．对水稻挥发性化合物的更进一步研究有两个方向,一是对存在于水稻体内,启动相关代谢途径的小分子信号物质的生理生化和分子生物学特性进行研究;二是研究捕食性节肢动物对信息化合物的接收、识别和学习等行为及与这些行为相关的生理生化和分子基础．     

Insect-based dog and cat food: A short investigative review on market,claims and consumer perception

The interest in use of insects for human food has also resulted in the appearance of insect-based dog and cat food products in the market. Insect-based pet food producers are using several health and sustainability claims for marketing purposes, which are expected to be the main drivers of market growth in the near future.In this paper, we systematically synthesize information about the insect-based pet food market, investigating the type of products commercially available, providing a geographical overview and type of insect species being commonly used in these products. We then try to synthesize information about health and sustainability claims currently being used by insect-based pet food companies in different geographies. Finally, we review information about consumer perception of: (1). these products in general; and (2). claims being used to market these products.The insect-based pet food market is growing rapidly in Europe. Recent regulatory approval in the USA will push this growth in the North American market too. It appears that consumers have connected very well with sustainability, hypoallergenicity and the overall gut health claims. Finally, insect-based pet food producers should: (1). adopt systematic marketing; (2). produce more scientific evidence; and (3). actively communicate and partner with veterinarians to improve the consumer perception of claims used on insect-based pet foods.     

Odor-mediated aggregation enhances the colonization ability of Drosophila melanogaster

Animal aggregation is a general phenomenon in ecological systems. Aggregations are generally considered as an evolutionary advantageous state in which members derive the benefits of mate choice and protection against natural enemies, balanced by the costs of limiting resources and intraspecific competition. Many insects use chemical information to find conspecifics and to form aggregations. In this study, we describe a spatio-temporal simulation model designed to explore and quantify the effects of the strength of chemical attraction, on the colonization ability of a fruit fly (Drosophila melanogaster) population. We found that the use of infochemicals is crucial for colonizing an area. Fruit flies subject to an Allee effect that are unable to respond to chemical information could not successfully colonize the area and went extinct within four generations. This was mainly caused by very high mortality due to the Allee effect. Even when the Allee effect did not play a role, the random dispersing population had more difficulties in colonizing the area and is doomed to extinction in the long run. When fruit flies had the ability to respond to chemical information, they successfully colonized the orchard. This happened faster, for stronger attraction to chemical information. In addition, more fruit flies were able to find the resources and the settlement on the resources was much higher. This resulted in a reduced mortality due to the Allee effect for fruit flies able to respond to chemical information. Odor-mediated aggregation thus enhances the colonization ability of D. melanogaster. Even a weak attraction to chemical information paved the way to successfully colonize the orchard.     

Multiple Ecological Factors Influence the Location of Proboscis Monkey (<Emphasis Type="Italic">Nasalis larvatus</Emphasis>) Sleeping Sites in West Kalimantan,Indonesia

Multiple ecological factors have been hypothesized to influence primate sleeping site selection. Testing multiple hypotheses about sleeping site selection permits examination of the relative strength of distinct ecological factors and expands our ability to understand how selection pressures influence primate sleeping behavior. Here we examine how avoidance of biting insects, thermoregulation, foraging efficiency, tree stability, and interspecific competition influence selection of sleeping sites by proboscis monkeys (Nasalis larvatus) in Indonesian Borneo. We collected data on relative insect abundance, temperature, rainfall, food availability, group size, sleeping site location, and presence of other primates for 12 mo. Using formal model comparison and information criteria, we analyzed the relative importance of these ecological factors in determining one aspect of sleeping site location: distance from the river. Our models supported the avoidance of biting insects and the foraging efficiency hypotheses. Proboscis monkeys slept further inland on nights when the abundance of sandflies was high along the river, and when less food was available along the river. Many studies suggest that primates select sleeping trees and locations to reduce predation risk; our study indicates that additional factors may also be important in determining sleeping site selection.     

Multimodal stimulation of Colorado potato beetle reveals modulation of pheromone response by yellow light

Orientation of insects to host plants and conspecifics is the result of detection and integration of chemical and physical cues present in the environment. Sensory organs have evolved to be sensitive to important signals, providing neural input for higher order multimodal processing and behavioral output. Here we report experiments to determine decisions made by Colorado potato beetle (CPB), Leptinotarsa decemlineata, in response to isolated stimuli and multimodal combinations of signals on a locomotion compensator. Our results show that in complete darkness and in the absence of other stimuli, pheromonal stimulation increases attraction behavior of CPB as measured in oriented displacement and walking speed. However, orientation to the pheromone is abolished when presented with the alternative stimulation of a low intensity yellow light in a dark environment. The ability of the pheromone to stimulate these diurnal beetles in the dark in the absence of other stimuli is an unexpected but interesting observation. The predominance of the phototactic response over that to pheromone when low intensity lights were offered as choices seems to confirm the diurnal nature of the insect. The biological significance of the response to pheromone in the dark is unclear. The phototactic response will play a key role in elucidating multimodal stimulation in the host-finding process of CPB, and perhaps other insects. Such information might be exploited in the design of applications to attract and trap CPB for survey or control purposes and other insect pests using similar orientation mechanisms.     

Establishment of Tools for Neurogenetic Analysis of Sexual Behavior in the Silkmoth,Bombyx mori

Background

Silkmoth, Bombyx mori, is an ideal model insect for investigating the neural mechanisms underlying sex pheromone-induced innate behavior. Although transgenic techniques and the GAL4/UAS system are well established in the silkmoth, genetic tools useful for investigating brain function at the neural circuit level have been lacking.

Results

In the present study, we established silkmoth strains in which we could visualize neural projections (UAS-mCD8GFP) and cell nucleus positions (UAS-GFP.nls), and manipulate neural excitability by thermal stimulation (UAS-dTrpA1). In these strains, neural projections and nucleus position were reliably labeled with green fluorescent protein in a GAL4-dependent manner. Further, the behavior of silkworm larvae and adults could be controlled by GAL4-dependent misexpression of dTrpA1. Ubiquitous dTrpA1 misexpression led both silkmoth larvae and adults to exhibit seizure-like phenotypes in a heat stimulation-dependent manner. Furthermore, dTrpA1 misexpression in the sex pheromone receptor neurons of male silkmoths allowed us to control male sexual behavior by changing the temperature. Thermally stimulated male silkmoths exhibited full sexual behavior, including wing-flapping, orientation, and attempted copulation, and precisely approached a thermal source in a manner similar to male silkmoths stimulated with the sex pheromone.

Conclusion

These findings indicate that a thermogenetic approach using dTrpA1 is feasible in Lepidopteran insects and thermogenetic analysis of innate behavior is applicable in the silkmoth. These tools are essential for elucidating the relationships between neural circuits and function using neurogenetic methods.