Interspecific Chemical Communication Research Articles

Novel insights into insect chemical communication – an introduction

The topics of insect chemical communication in this issue can be subdivided into intra- and interspecific signaling mechanisms. For intraspecific chemical communication, several articles characterize sexual cues involved in mate recognition and mating behavior, others discuss mechanisms associated with the neurobiology of chemoreception. For interspecific chemical communication, one article links an olfactory recognition mechanism to a phoretic relationship, i.e., using a heterospecific organism for dispersal. Another identifies a parasitoid-derived mortality-inducing protein, and discusses its potential for biological pest control.

Interspecific chemical communication for synchronous regulation of the population of the apple tree main pests

Interspecific chemical communication for synchronous regulation of the population of the apple tree main pests

Histological and Immunohistochemical Characterization of Vomeronasal Organ Aging in Mice.

Simple SummaryChemical communication has been intensely studied and the importance of its role in animal life has been ascertained. Located in the nasal cavity, the vomeronasal organ is one of the main actors in charge of chemical reception. Alterations of this organ have proven to modify behavioral responses to semiochemical expositions. For all the other organs, a well-known origin of alteration is aging. The objective of this study was to analyze this effect on the vomeronasal organ condition and to determine the nature of these potential changes. This study demonstrates that this organ is significantly impacted by aging. In particular, old mice present strong signs of neuronal degeneration compared to adults.The vomeronasal organ (VNO) plays a crucial role in animal behavior since it is responsible for semiochemical detection and, thus, for intra- and interspecific chemical communication, through the vomeronasal sensory epithelium (VNSE), composed of bipolar sensory neurons. This study aimed to explore a well-recognized cause of neuronal degeneration, only rarely explored in this organ: aging. Murine VNOs were evaluated according to 3 age groups (3, 10, and 24 months) by histology to assess VNSE changes such as cellular degeneration or glycogen accumulation and by immunohistochemistry to explore nervous configuration, proliferation capability, and apoptosis with the expression of olfactory marker protein (OMP), Gαi2, Gαo, Ki-67, and cleaved caspase-3 proteins. These markers were quantified as percentages of positive signal in the VNSE and statistical analyses were performed. Cellular degeneration increased with age (p < 0.0001) as well as glycogen accumulation (p < 0.0001), Gαo expression (p < 0.0001), and the number of cleaved-caspase3 positive cells (p = 0.0425), while OMP and Gαi2 expressions decreased with age (p = 0.0436 and p < 0.0001, respectively). Ki67-positive cells were reduced, even if this difference was not statistically significant (p = 0.9105). Due to the crucial role of VNO in animal life, this study opens the door to interesting perspectives about chemical communication efficiency in aging animals.

Formica francoeuri responds to pheromones and defensive chemical cues of social bees

Insects must detect and respond to diverse chemical cues in a complex chemical landscape. Intraspecific and intraguild communication have received a lot of attention, especially among bee taxa. However, little is known about interspecific chemical communication in general and in non-bees in particular. Ants, such as Formica francoeuri, also are opportunistic floral visitors who seek the carbohydrate-rich rewards of flowers. Thus, these ants likely encounter aggressive competitors for nectar, such as bees. Here, we performed a series of experiments to examine how ant foragers respond to bee pheromones, venom and sting glands in the context of foraging. Understanding how ants utilize non-target chemical cues will identify previously cryptic interactions and provide new insights into the hidden mechanisms governing foraging decisions. As the foraging decisions by floral visitors have a direct impact on the pollination mutualism, studies such as this will help us build better predictive models of plant–pollinator networks and develop hypotheses as to how these interaction networks may change with shifts in the floral visitor community.

Chemical signatures of femoral pore secretions in two syntopic but reproductively isolated species of Gal\xe1pagos land iguanas (Conolophus marthae and C. subcristatus)

The only known population of Conolophus marthae (Reptilia, Iguanidae) and a population of C. subcristatus are syntopic on Wolf Volcano (Isabela Island, Galápagos). No gene flow occurs suggesting that effective reproductive isolating mechanisms exist between these two species. Chemical signature of femoral pore secretions is important for intra- and inter-specific chemical communication in squamates. As a first step towards testing the hypothesis that chemical signals could mediate reproductive isolation between C. marthae and C. subcristatus, we compared the chemical profiles of femoral gland exudate from adults caught on Wolf Volcano. We compared data from three different years and focused on two years in particular when femoral gland exudate was collected from adults during the reproductive season. Samples were processed using Gas Chromatography coupled with Mass Spectrometry (GC–MS). We identified over 100 different chemical compounds. Non-Metric Multidimensional Scaling (nMDS) was used to graphically represent the similarity among individuals based on their chemical profiles. Results from non-parametric statistical tests indicate that the separation between the two species is significant, suggesting that the chemical profile signatures of the two species may help prevent hybridization between C. marthae and C. subcristatus. Further investigation is needed to better resolve environmental influence and temporal reproductive patterns in determining the variation of biochemical profiles in both species.

The scent of emotions: A systematic review of human intra- and interspecific chemical communication of emotions.

ObjectiveThe sense of olfaction has been considered of minor importance in human communication. In recent years, evidence has emerged that humans might be influenced by unconscious messages sent through chemosignals in body odors. Data concerning the ability of humans to recognize fear, maybe related to the evolutionary role of these emotions in the fight‐or‐flight reactions, are well known.MethodsTo further understand the role of emotional chemosignals in mediating communication in humans and its influence on animal behaviors, we conducted a systematic literature review.ResultsChemosignals derived from axillary odors collected under a variety of emotional stimuli and sad tears in humans affect receivers' social interactions, danger detection and risk‐taking behavior, social aspects of eating, and performance under stressing conditions. In addition, beyond the fight‐or‐flight response, even the body odors of happiness can be perceived by others. Furthermore, human chemosignals can influence behaviors and stressful responses in animals, particularly dogs and horses, which may partially explain their special relationship with humans.ConclusionOur review highlights the importance of chemosignaling in human intra‐ and interspecific interactions and suggests the need for further investigations, both in physiological conditions and in patients with psychiatric or neurodegenerative disorders.

Are Drosophila preferences for yeasts stable or contextual?

Whether there are general mechanisms, driving interspecific chemical communication is uncertain. Saccharomycetaceae yeast and Drosophila fruit flies, both extensively studied research models, share the same fruit habitat, and it has been suggested their interaction comprises a facultative mutualism that is instigated and maintained by yeast volatiles. Using choice tests, experimental evolution, and volatile analyses, we investigate the maintenance of this relationship and reveal little consistency between behavioral responses of two isolates of sympatric Drosophila species. While D. melanogaster was attracted to a range of different Saccharomycetaceae yeasts and this was independent of fruit type, D. simulans preference appeared specific to a particular S. cerevisiae genotype isolated from a vineyard fly population. This response, however, was not consistent across fruit types and is therefore context‐dependent. In addition, D. simulans attraction to an individual S. cerevisiae isolate was pliable over ecological timescales. Volatile candidates were analyzed to identify a common signal for yeast attraction, and while D. melanogaster generally responded to fermentation profiles, D. simulans preference was more discerning and likely threshold‐dependent. Overall, there is no strong evidence to support the idea of bespoke interactions with specific yeasts for either of these Drosophila genotypes. Rather the data support the idea Drosophila are generally adapted to sense and locate fruits infested by a range of fungal microbes and/or that yeast–Drosophila interactions may evolve rapidly.

Behavioral responses of the egg parasitoid Trissolcus japonicus to volatiles from adults of its stink bug host, Halyomorpha halys

Halyomorpha halys, originating from East Asia, has become an important agricultural pest in northern temperate regions since its accidental introduction into North America in the mid-1990s and Europe in 2007. Trissolcus japonicus is the predominant egg parasitoid of this pest in its native range. Here, we tested the hypothesis that T. japonicus uses volatiles associated with H. halys adults during host location. The effects of these volatile compounds on H. halys adults were also assessed. Chemical analysis with GC-MS and electrophysiological analysis with GC-EAD revealed the presence of two bioactive volatile compounds from H. halys adults, n-tridecane and (E)-2-decenal. In the Y-tube assays, female T. japonicus were attracted by n-tridecane but strongly repelled by (E)-2-decenal. Furthermore, host searching time of female T. japonicus was significantly reduced when an H. halys egg mass was treated with n-tridecane and prolonged when treated with (E)-2-decenal or a mixture of (E)-2-decenal and n-tridecane. Male H. halys were significantly attracted by n-tridecane, whereas females had no response to this compound in the Y-tube assays. (E)-2-Decenal strongly repelled male and female H. halys in the Y-tube assays. We discuss the multifunctional kairomonal and other possible roles of these semiochemicals at different trophic levels in the context of intra- and inter-specific chemical communication, in the H. halys–T. japonicus system.

Interspecific chemical communication in raids of the robber bee Lestrimelitta limao

Most social bees collect floral resources to obtain proteins and carbohydrates. However, the obligate cleptoparasite stingless bee Lestrimelitta limao, the so-called robber bee, is a rare exception as it collects resources by raiding other stingless bee nests. The mechanisms these bees use to overcome host colony defenses are poorly understood. Many host species retreat inside the nest during L. limao attacks and the signals triggering this behavior require a better understanding. While some researchers have proposed that robber bees release chemical compounds that are responsible for host retreat, others have hypothesized that the observed behavior results from communication among host workers. In order to investigate the role of interspecific signals in raids, we tested the effects of robber bees’ mandibular and labial gland secretions on the behavior of Frieseomelitta varia workers. We combined behavioral assays with chemical and electrophysiological analyses. We found that citral and 9-nonacosene are major mandibular gland compounds and two esters, hexadecyl acetate and 9-hexadecenyl acetate, are major labial gland compounds. These three major compounds elicited electro-physiological responses on host worker antennae. Robber bee labial gland extracts repelled both foragers and guards, while mandibular gland content increased aggression. Our results suggest that interspecific communication plays a role during natural raids and that esters from L. limao labial glands, rather than citral, are more likely to trigger the host retreat. The results add to our knowledge about L. limao chemical communication and help to elucidate the mechanisms involved in their intriguing foraging strategy.

Kairomones - important substances in interspecific communication in vertebrates: a review

Interspecies chemical communication is widespread among many groups of organisms, including vertebrates. Kairomones belong to a group of intensively researched substances, represent means for interspecific chemical communication in animals and bring benefit to the acceptor of the chemical signal. Important and often studied is the chemical communication between hosts and their ectoparasites such as ticks and other parasitic mite species. Uric acid is a host stimulus of the kairomone type, which is a product of bird metabolism, or secretions of blood-fed (ingested) ticks. Secretion of volatile substances with kairomone effect may depend on the health of the host organism. Another examined group is the haematophagous ectoparasite insects of the order Diptera, where in addition to the attractiveness of CO&lt;sub&gt;2&lt;/sub&gt; a number of other attractants have been described. Specificity of substances in chemical communication can also be determined by their enantiomers. Detailed study of the biology of these ectoparasites is very important from a practical point of view: these parasites play an important role as vectors in a number of infectious diseases. Another area of interspecific chemical communication is the predator-prey relationship, or rather the ability to detect the proximity of predator and induce anti-predator behaviour in the prey. This relationship has been demonstrated in aquatic vertebrates (otter Lutra lutra &amp;ndash; salmon Salmo salar) as well as in rodents and their predators. The substances produced by carnivores that induce behavioural response in mice have already been identified. The knowledge of interspecies communication (e.g., between host and parasite) is becoming a prerequisite in successful animal breeding and care.

NOVEL FEATURES OF AN INDUCIBLE DEFENSE SYSTEM IN LARVAL TREE FROGS (HYLA CHRYSOSCELIS)

Organisms in aquatic ecosystems must often tolerate variable environmental conditions, including an uncertain risk of predation. Individuals that can maintain plastic defenses against predation will increase their survival when predators are present, but will not incur the costs of these defenses when the risk of predation is low and the defense is not induced. Larvae of the pond-breeding anuran Hyla chrysoscelis develop a conspicuous phenotype in the presence of predators consisting of a brightly colored tail and a deeper tail fin. In this study, I attempted to identify the source of the chemical signal that induces this defensive morphology in this species. I tested whether metabolites alone, originating from the prey but passing through the predator, were able to induce the same morphological response as the combination of alarm signals released directly by attacked conspecifics, and metabolites. I used morphometric and tail conspicuousness data to assess tadpole response to the perceived risk of predation by larval odonate predators (Anax junius). I also tested whether this inducing cue could be recognized across species by measuring the morphological response of H. chrysoscelis tadpoles exposed to cues emitted when tadpoles of a closely related genus (Pseudacris crucifer) were consumed. Tadpoles exhibited a clean graded response of both overall shape and tail morphology in response to all cues, corresponding to their relative reliability as indicators of a risk of predation. H. chrysoscelis tadpoles were also able to respond to cues emitted when tadpoles of a closely related genus were consumed by predators. These results illustrate that tadpoles of this species are able to respond to metabolites alone without alarm signals, and that interspecific chemical communication is a primary mechanism for predator avoidance in this inducible defense system.

Fatty acids mediate aggressive behavior in the spider Tegenaria atrica

The aggressiveness of the house spider (Tegenaria atrica) has a chemical basis in terms of intra- and interspecific chemical communication. Vibrations are used for longer range detection of intruders on the web territory whereas cuticular lipids mediate shorter range agonistic behaviors. Two cuticular acids were shown to promote aggressive responses from adult spiders, whereas mixtures of cuticular alkanes acted as inhibition signals.

Variations in chemical mimicry by the ectoparasitic mite Varroa jacobsoni according to the developmental stage of the host honey-bee Apis mellifera

The ectoparasitic mite Varroa jacobsoni poses a major threat to the survival of European honey-bee populations. Development of effective control methods is therefore much needed. Study of interspecific chemical communication between the parasite and host is a particularly promising avenue of research. Previous study has shown that the cuticular hydrocarbons of the parasite mite Varroa jacobsoni are qualitatively identical to those of its honey-bee host Apis mellifera (Nation J.L., Sanford M.T., Milne K., 1992. Cuticular hydrocarbons from Varroa jacobsoni. Experimental and Applied Acarology 16, 331–344). The purpose of the present study was to compare the cuticular hydrocarbon patterns of the two species at different stages of bee development. Cuticular components were identified by gas chromatography/mass spectrometry. The proportion of each component was calculated at three stages of bee development (larvae, pupa, emerging bee). The degree of chemical mimicry between the parasite and host was evaluated by multivariate analyses using the resulting proportions for each category of individuals. There were four main findings. The first was that the proportions of some components are different at the larval, pupal and imago stage of bee development. Second, Varroa profiles vary depending on the developmental stage of the host. Third, the cuticular profile of adult mites is more similar to that of the stage of the host than that of later and/or earlier stages except for parasites collected from emerging adult bees. Fourth, the degree of mimicry by Varroa is greater during larval and pupal stages than during the emerging adult bee stages. The role of chemical mimicry — although it is not perfect — in enabling parasites to infest bee colonies by the parasite is discussed.

Enantiomerically Pure Insect Pheromones: The Carbohydrate Synthetic Approach

1. Introduction During the past two decades, there has been a rapidly growing interest in the field of intra- and interspecific chemical communication. Insect pheromones in particular have been intensely studied with respect to their potential use as a component of integrated pest management.1 Structural identification and chemical synthesis of these so-called “semiochemicals” have developed in harmony with the biological research evaluating structure-activity relationships. Most of the pheromones identified, studied, and synthesized come from the order Lepidoptera: very often these pheromones consist of long-chain olefinic compounds in which regio- and cis/trans-isomerism determine their biological activity. Several well documented reviews have appeared, emphasizing both coupling of alkyl halides or similar electrophilic substrates with metallo-organic reagents (“Wurtz-chemistry”) and carbonyl olefination, such as the Wittig reaction and its huge variety of modifications for regio- and stereoselective C-C bond formation. 2-8 The importance of chirality in pheromone perception by insects has been recognized and the role of optical isomerism and diastereoisomerism in behavioral discrimination has been firmly established through the combination of synthesis and bioassay. Some reviews bring good insight into the diverse strategies employed in synthesizing chiral pheromones, 8,9 originating principally from the orders Coleoptera and Hymenoptera. In spite of the increasing efficiency of asymmetric synthesis in the semiochemical field 10 , only few methods afford highly optically pure compounds with known absolute configuration. On the other hand, optical resolution is not always satisfactory and the absolute configuration of the resolved material has to be determined by some means. 11 Enantiospecific synthesis starting from naturally occuring chiral molecules such as amino or hydroxy acids, terpenes and sugars appears to be the safest path leading to highly optically pure pheromones. The prominent role of readily available carbohydrate starting materials within this “chiral synthon approach” has been clearly demonstrated. 12 The present review offers a 1976 to 1990 literature survey of the use of hexoses (mainly D-glucose and derivatives) and pentoses for the enantiospecific synthesis of chiral pheromones, issuing principally from the order Coleoptera. 13

Physiology of interspecific chemical communication in Heliothis moths

Abstract Electroantennograms were recorded from the antennae of adult male and female corn earworms, Heliothis zea (Boddie). A total of seventeen female moth sex pheromone components from several species were tested. Of these, two components elicited significantly greater responses than the other fifteen. These were (Z)‐11‐hexadecenal, a conspecific component, and (Z)‐9‐tetradecenal, a component found in the pheromone blend of a sympatric species H.virescens (F.) that inhibits attraction of H.zea males. The results from dose‐response and selective adaptation studies indicate that there are separate populations of receptors for these two chemical signals on the antenna of male H.zea. The more sensitive population is selective for (Z)‐11‐hexadecenal, while the less sensitive one responds to (Z)‐9‐tetradecenal. These findings provide a physiological basis by which H.zea males can distinguish the interspecific repellent from the conspecific pheromone blend. It is likely that this discrimination contributes to reproductive isolation between these two species.

Robber bees (Lestrimelitta limao) and their host chemical and visual cues in nest defense byTrigona (Tetragonisca) angustula (Apidae: Meliponinae)

The nest of the stingless bee,Trigona (Tetragonisca) angustula, is guarded by bees positioned in the nest entrance and others hovering in front of it. Hovering guard bees track returning foragers sideways along the last 10 cm in front of the nest, but intercept and incapacitate nest intruders by clinging with mandibles to wings and legs. When attacked by the cleptobiotic stingless beeLestrimelitta limao, the colony strengthens its aerial defense with hundreds of additional hoverers. To test our hypothesis that this reaction is due to interspecific chemical communication based on kairomone effects, we presented synthetic cephalic volatiles of both species at the nest entrance and counted the number of bees leaving the nest and taking up hovering positions. We conclude that guard bees recognizeL. limao by the major terpenoids of their volatile cephalic secretions, geranial, neral (=citral) and 6-methyl-5-hepten-2-one; other components may fine-tune this recognition. The effect of chemical stimuli is not significantly enhanced by combination with a dummy ofL. limao. Guard bees, we hypothesize, respond to this kairomone by secreting a species specific alarm pheromone; a major component of this pheromone, benzaldehyde, recruits additional bees to defend the nest.

House fly oviposition inhibition by larvae ofHermetia illucens, the black soldier fly

Wild populations of house flies were inhibited from ovipositing into poultry manure containing larvae of the black soldier fly,Hermetia illucens (L.). A laboratory strain of house fly responded differently, readily ovipositing into manure with lower densities of soldier fly larvae, but avoiding the higher densities tested. The amount of timeH. illucens larvae occupy the manure prior to an oviposition test influences ovipositional responses of house flies. Manure conditioned byH. illucens larvae for 4-5 days did not significantly inhibit house fly oviposition. We suggest that some type of interspecific chemical communication (allomone) is present.

Thanasimus dubius: Prey perception

The predator Thanasimus dubius follows aggregations of the southern pine beetle, Dendroctonus frontalis, in response to pheromones released by its prey. Especially, synthetic frontalin (1,5-dimethyl-6,8-dioxa-bicyclo[3.2.1]octane) evokes spontaneous concentrations of both male and female T. dubius. It leads the predator population to intercept prey and to encounter mates as well. The interspecific chemical communication provides T. dubius with a degree of spatial synchronization of foraging and mating unusual in predator-prey systems.