Insect Pheromones Research Articles

A simple model for simulation of insect pheromone dispersion within forest canopies

Synthetic pheromones and other behavioral chemicals are used by land managers to prevent insect-caused tree mortality or crop failure in forest and agricultural systems. Currently, no method exists to continuously measure pheromone concentration or movement in real-time. To improve our understanding of pheromone fate and transport under different forest canopies, results from a set of surrogate pheromone (sulfur hexafluoride tracer) experimental trials were used to evaluate a simple, instantaneous, three-dimensional Lagrangian dispersion model. The model was designed to predict both instantaneous and time-averaged pheromone concentrations. Overall, the results from the model show simulated time-averaged arc maximum concentrations within a factor of two of the observed data. The model correctly matched the sharp peaks and narrow widths of the meandering plumes observed in the instantaneous data, however the magnitude of the instantaneous peaks was often under-estimated. This model and evaluation provide the basis for a tool that can be used to guide deployment of synthetic pheromones or other semiochemicals for monitoring, mass trapping, or disruption of mating or aggregation.

High-throughput ESI-MS analysis of binding between the Bombyx mori pheromone-binding protein BmorPBP1, its pheromone components and some analogues

Chip-assisted high-throughput ESI-MS analysis of the pheromone-binding protein of the silkworm moth Bombyx mori, BmorPBP1, incubated with its pheromone components bombykol, bombykal and analogues was developed. The protein bound to bombykol ((10E,12Z)-hexadecadien-1-ol) and all 3 of its geometric isomers to a lesser extent, and showed relaxed specificity toward different chain lengths possessing unsaturation. BmorPBP1 did not bind to bombykal ((10E,12Z)-hexadecadienal), demonstrating molecular recognition of the insect pheromone components.

Insect pheromone research in South America

Insect pheromone research has a long and rich history built up primarily by studies conducted in the Northern hemisphere. Not surprisingly, these studies have largely targeted species relevant to these regions of the world, for the most part agricultural and forest pests. Pheromone research in South American countries came a few decades behind, albeit their strong dependence in agriculture and therefore in pest management. In the last 20 years, a combination of economic, environmental and technical factors have come together to generate a small but rising number of chemical ecologists working in pheromone chemistry and biology in South America. In this article we summarize the results of this trend. We review pheromone studies in which South American scientists have participated in collaboration with foreign scientists, mostly chemistry groups, as well as the ever-growing number of studies carried out completely within the region. We have focused mainly in research involving the characterization of pheromones from native species, which involve the most important insect orders, namely Lepidoptera, Coleoptera, Heteroptera and Hymenoptera. We also present a simple meta-analysis including geographical distribution, trends in collaborative or independent work, and a 20-year evolution of published articles in the field. Finally, we emphasize the importance of a coordinated effort to further promote the growth of this field in Latin America, through the endorsement of international collaborations within the region. Such goal would be facilitated by a regional academic organization, which would in turn initiate the occurrence of regular scientific meetings.

Environmentally regulated abiotic release of volatile pheromones from the sugar-based oral secretions of caribflies

We report an abiotic mechanism for the emission of volatile insect pheromones that is controlled by environmentally induced change in the physicochemical properties of the sugar-based release matrix. Male Anastrepha suspensa (Loew) (caribflies) mark mating sites on leaf surfaces by depositing oral secretions that contain sugar, as well as, γ-hydroxy acid and γ-lactone forms of the diastereomeric aggregation pheromones, epianastrephin and anastrephin. The γ-hydroxy acids extend emission over many days via aqueous equilibrium with the thermodynamically less preferred, but more volatile, γ-lactones (∼100:1). A kinetic model, which supports a γ-lactone diffusion-limited rate, was generated and tested by measuring the effect of temperature and humidity under fixed and ambient atmospheric inputs, respectively. Results show that pheromone release from the markings occurs with a periodicity that parallels relative humidity and complements the daily pattern of the caribflies’ reproductive and aggregative activity. This study provides an example of a physicochemical-based inter-organism communication strategy that has been mechanistically linked to the abiotic environmental processing of volatile chemical signals. The exploitation of this natural connectivity will spur environmentally sustainable chemistries, particularly pheromone-based alternatives to insecticide application.

Biosynthetic pathways of the pheromone of the Egyptian armyworm Spodoptera littoralis

Abstract Most insect pheromones comprise multicomponent blends of geometric or optical isomers, and one major question is how insects produce species‐specific ratios of components for successful reproductive isolation. Key enzymes suggested to be involved in pheromone biosynthesis are acetyl‐coenzyme A carboxylase and fatty acyl synthetase, chain‐shortening enzymes, desaturases, elongases, reductases, oxidases, and alcohol acetyl transferases. The female pheromone composition of the Egyptian armyworm Spodoptera littoralis (Boisd.) is highly dependent on the origin of the strain. In this review, we present a summary of the different reported pheromone compositions of the moth, including from our recent studies on this subject, as well as the biosynthetic routes to the different components and the molecular approaches involved. In addition, the key role played in the proposed biosynthetic pathways by a number of important biosynthetic enzymes, such as chain shortening enzymes, desaturases and alcohol acetyl transferases, is outlined, as well as the latest developments on the inhibition of these enzymes.

The utilization and industrialization of insect resources in China

AbstractInsecta is the biggest group of animals on earth. The insects are thought to be one of the biggest biological resources that have not been fully exploited by humans. China is one of the earliest countries to exploit insect resources in the world and has been the top producer for over one thousand years of many insect‐related industrial products, such as silk, insect wax and Chinese gallnuts. The exploitation and industrialization of insect resources in China is generally classified into four different levels. The first level is the direct utilization of insect bodies and their secretions, the history of which can be traced back for thousands of years. This level includes the culture and utilization of the silkworm Bombyx mori, the Chinese honeybee Apis cerana cerana, the Chinese white‐wax scale Ericerus pela, the Chinese gall aphid Schlechtendalia chinensis, and the lac insects Kerria spp. Additionally, numerous other insects are typically used for Chinese traditional medicines and food, such as Eupolyphaga sinensis, Opisthoplatia orientalis, Aspongopus chinensis, Martianus dermestoides, Polyrhachis vicina, Hepialus spp, Vespa, Hydrillodes repugnalis, and Tenebrio molitor. Pollinators (Megachile rotundata, Osmia cornifrons, O. excavata) and ornamental insects like butterflies, katydids Gampsocleis grafiosa, and fighting crickets Scapsipedes micado are also among the insects included in this level. Accordingly, a related industry is insect‐breeding, including sericulture and apiculture, which lays the basis for all insect industrialization. The second level is the utilization of insects as enemies of pests and insect pathogens for biological control. The enemy insects, including the egg parasites tricogramma Trichogramma spp, the seven spotted lady beetle Coccinella septempunctata, the Chinese green lacewing Chrysopa sinica, and Anastatus sp. could be produced in large scale. The insect pathogens that have been extensively used for commercial biocontrol in China include Helicoverpa armigera Nucleopolyhedrovirus (HaSNPV), Ectropis oblique Nucleopolyhedrovirus (EcobNPV), Spodoptera exigua multicapsid nucleopolyhedrovirus (SeMNPV), Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV), Plutella xylostella Granulosis (PxGV), Pieris rapae granulosis (PiraGV), and Bacillus thuringiensis (Bt). Related industries include the biopesticide industry and the enemy insect production industry. The third level of utilization is the extraction and synthesis of insect materials with diverse bioactivities. Some insect pheromones and hormones extracted from insect bodies or chemically synthesized have been used for insect pest control and for regulating the silkworm breeding. Toxins from honeybees and wasps have been used in medicine. Some insect materials from the larvae of honeybees, silkworms, tasar silkworms, and houseflies have been developed into health products. The fourth level is using the insects as bioreactors to produce peptides for medical and veterinary uses. Hundreds of foreign genes have been successfully expressed in the insect cells and larvae. The hGM‐CSF expressed in silkworm pupae is commercially available. In this article, we review the culture and utilization of important industrial insects in China.

Copper-catalyzed cross-coupling of (Z)-allyl phenyl ethers with Grignard compounds in the synthesis of insect pheromones

(8Z)-Dodec-8-en-1-yl acetate (pheromone of oriental fruit moth Grapholita molesta) and (9Z)-dodec-9-en-1-yl acetate (pheromone of grape berry moth Paralobesia viteana) containing impurities of isomeric structures were synthesized via copper-catalyzed cross-coupling of (Z)-1-phenoxyhex-2-ene and (Z)-1-phenoxypent-2-ene, respectively, with Grignard compounds in the key stage.

Scent of a Fly

Sexual courtship is a highly ritualized behavior in many animals. Recent work in the vinegar fly, Drosophila melanogaster, has illuminated how the pheromone cis-vaccenyl acetate modulates sexual behavior in the fly. Chemosensory receptors and a sexually dimorphic circuit activated by this pheromone have been identified. This minireview highlights recent advances in the field of fly courtship.

Natural variation in Pristionchus pacificus insect pheromone attraction involves the protein kinase EGL-4

The geographical mosaic theory of coevolution predicts that different local species interactions will shape population traits, but little is known about the molecular factors involved in mediating the specificity of these interactions. Pristionchus nematodes associate with different scarab beetles around the world, with Pristionchus pacificus isolated primarily from the oriental beetle in Japan. In particular, the constituent populations of P. pacificus represent a rare opportunity to study multiple specialized interactions and the mechanisms that influence population traits at the genetic level. We identified a component of the cGMP signaling pathway to be involved in the natural variation for sensing the insect pheromone ETDA, using targeted introgression lines, exogenous cGMP treatment, and a null egl-4 allele. Our data strongly implicate egl-4 as one of several loci involved in behavioral variation in P. pacificus populations. That EGL-4 homologs have been independently implicated for behavioral variations in other invertebrate models suggests that EGL-4 may act as a modulator for interspecies behavioral repertoires across large phylogenetic distances.

Preparation of Substituted Enol Derivatives From Terminal Alkynes and Their Synthetic Utility

Stereodefined enol derivatives of aldehydes are prepared from terminal alkynes. Specifically, terminal alkynes are known to undergo Cp2ZrCl2-catalyzed methylalumination. Here, we show that the resultant vinylalanes can be oxygenated with peroxyzinc species to generate trisubstituted enolates. Electrophilic trapping with carboxylic anydrides or silyl triflates yields trisubstituted enol esters or silanes, respectively. The tandem carbometalation/oxygenation tolerates free and protected alcohols, heterocycles, olefins, and nitriles. Stereodefined enol esters can undergo asymmetric dihydroxylation to yield optically active alpha-hydroxy aldehydes. Reduction with NaBH4 provides the diols of 1,1-disubstituted olefins in excellent ee. An application of this methodology to the enantioselective synthesis of the insect pheromone frontalin is presented. Finally, alpha-hydroxy aldehydes are shown to undergo homologation to a terminal alkyne, reductive amination, oxidation and olefination. Preliminary results indicate that tandem carbometalation/amination can be accomplished with azodicarboxylates. In this way, ene-hydrazines are formed in excellent yield.

Modelling of concentrations along a moving observer in an inhomogeneous plume. Biological application: model of odour-mediated insect flights

We develop a stochastic model for the time-evolution of scalar concentrations and temporal gradients in concentration experienced by observers moving within inhomogeneous plumes that are dispersing within turbulent flows. In this model, scalar concentrations and their gradients evolve jointly as a Markovian process. Underlying the model formulation is a natural generalisation of Thomson’s well mixed condition [Thomson DJ (1987) J Fluid Mech 180:529–556]. As a consequence model outputs are necessarily compatible with statistical properties of scalars observed in experiment that are used here as model input. We then use the model to examine how insects aloft within the atmospheric boundary-layer can locate odour sources by modulating their flight patterns in response to odour cues. Mechanisms underlying odour-mediated flights have been studied extensively at laboratory-scale but an understanding of these flights over landscape scales is still lacking. Insect flights are simulated by combining the stochastic model with a simple model of insect olfactory response. These simulations show the strong influence of wind speed on the distributions of the times taken by insects to locate the source. In accordance with experimental observations [Baker TC, Vickers NJ (1997) In: Insect pheromone research: new directions, pp 248–264; Mafra-Neto A, Carde RT (1994) Nature 369:142–144], flight patterns are predicted to become straighter and shorter, and source location is predicted to become more likely as the mean wind speed increases. The most probable arrival time to the source decreases with the mean wind speed. It is shown that scale-free movement patterns arising from olfactory-driven foraging stem directly from the power-law distribution of concentration excursion times above/below a threshold level and are robust with respect to variations in Reynolds number. Flight lengths are well represented by a power law distribution in agreement with the observed patterns of foraging bumblebees [Heinrich B (1979) Oecologia 40(3):235–245].

Components of the Essential Oil from Adenophora triphylla var. japonica

The chemical composition of the essential oil from Adenophora triphylla var. japonica has been investigated by GC and GC/MS. As a result, 82 volatile components were detected, which contained three insect pheromones, (Z,Z,Z)-1,3,6,9-heneicosatetraene (3.6%), (Z,Z,Z)-3,6,9-heneicosatriene (2.8%) and (Z,Z)-6,9-heneicosadiene (1.8%) as characteristic compounds of the oil.

A preliminary study for identifying olfactory markers of fear in the rat

In stressful situations, many animals release alarm pheromones to warn conspecifics of impending danger. The authors sought to establish experimental conditions for a larger study aimed at identifying alarm pheromones emitted by the rat. They placed rats in a specially designed chamber and exposed them to aversive tactile, visual and acoustic stimuli over the course of a few days. The researchers observed rats' behavior and analyzed air samples taken from their immediate environment under the following conditions: (i) when rats were unstressed; (ii) immediately after rats were exposed to aversive stimuli; and (iii) when rats were left alone in the chamber after being conditioned to fear imminent aversive stimuli. Stressed rats emitted several substances that are known to function as alarm pheromones in insects. When previously unstressed control rats were exposed to these same substances, they had a distinct behavioral fear response.

パラジウム錯体触媒による置換アレン類の立体選択的合成法の開発とその応用

A novel Pd-catalyzed reaction of a 2-halo- or 2-trifloxy-l, 3-butadiene derivative with a soft nucleophile is developed. The reaction proceeds via an exo-alkylidene-π-allylpalladium intermedi-ate in a formal SN2' fashion to give an allenic compound exclusively. A variety of soft nucleophiles, such as malonates, phenoxides, and imides, are applicable to the reaction, and thus a wide range of functionality can be introduced to the products. The reaction is extended into an asymmetric counterpart and axially chiral allenes are prepared with up to 93% ee by the use of chiral palladium catalysts. A formal total synthesis of an insect pheromone is achieved using the Pd-catalyzed asymmetric reaction as a key step. The Pd-catalyzed reaction also enables to prepare axially chiral (allenylmethyl) silanes and allenylsilanes in optically active forms. Reactions of these silylallenes with appropriate electrophiles proceed via SE', pathways and the allenic axial chirality is efficiently transferred to stereogenic carbon centers in the SE', products.

Evaluation of porous silica glasses as insect pheromone dispensers

Este trabalho demonstra a viabilidade da utilizacao de vidros porosos como materiais para armazenar e liberar feromonios de insetos, visando o controle de pragas na agricultura. Feromonios de diferentes insetos foram impregnados em vidros porosos do tipo Vycor (PVG), e o material impregnado foi caracterizado por espectroscopia de absorcao no infravermelho. A determinacao da taxa de liberacao do feromonio em laboratorio, bem como o teste pratico de captura de insetos em diferentes plantacoes, foram subsequentemente realizados. Foram realizados testes com feromonios da Grapholita molesta (Lepidoptera: Tortricidae) e Leucoptera coffeella (Lepidoptera: Lyonetiidae), as principais pestes da maca e cafe, respectivamente, em plantacoes brasileiras. Verificou-se que a taxa de liberacao do feromonio depende do tipo de interacao com as paredes dos poros do PVG. Os resultados indicaram uma boa performance do PVG, semelhante a de septos de borracha utilizados comercialmente como liberadores. Estes resultados, somados ao fato de que o PVG nao e nocivo ao meio ambiente e pode ser reutilizado em varios ciclos de impregnacao e liberacao, fazem destes vidros porosos candidatos em potencial para aplicacao no controle de pragas na agricultura. This work demonstrates the viability and advantages of using porous silica glass as an insect pheromone dispenser, in order to control insect population in agriculture. Pieces of so-called Porous Vycor Glass (PVG) were impregnated with pheromones of different insects (both consisting of a single compound or a mixture of compounds). Studies were conducted to characterize the impregnated-PVG and to determine the pheromone release ratio under laboratory conditions. The practical application was verified in two different plantation areas, using the PVG impregnated with pheromone from Grapholita molesta (Lepidoptera: Tortricidae) and Leucoptera coffeella (Lepidoptera: Lyonetiidae), the main pests of apple and coffee plantations in Brazil, respectively. The release rate was dependent on the interaction between the molecules of the impregnated pheromone and the surface of the PVG pores. A good performance of the porous glass was observed, similar to that of rubber septa commercially used as pheromone dispensers.

Spatial relationships between two Agriotes click‐beetle species and wireworms in agricultural fields

Abstract1 The production of new insect pheromones for pest monitoring proceeds at a greater rate than their evaluation, with the consequential possibility of premature introduction. Fundamental to their successful deployment is the determination of a consistent relationship between adult male pheromone trap catches and pest damage. In the present study, adult pheromone traps and larval bait traps were used to examine spatial relationships between two species of Agriotes beetle and wireworms at the field scale.2 The spatial distributions of adult male Agriotes lineatus and Agriotes obscurus in two fields were determined and compared with the distribution of their larvae. Data were assembled as spatially referenced trap counts, and analysed for evidence of aggregation and clustering using Spatial Analysis by Distance IndicEs (SADIE) methodology. Spatial stabilities of adult populations between sampling dates were tested using association tests. Spatial and quantitative linkages between adult and larval trap catches were also tested. Moreover, a new way of adapting SADIE methodologies is presented for situations where two datasets within an area do not share the same sampling points.3 There was no significant difference in variance : mean relationships for the two species but there were differences in their spatial distributions, and this is a definitive example of the general argument stating that it is important to consider spatial as well as count data in ecological studies. The spatial distribution of A. lineatus varied between sampling occasions at both sites whereas A. obscurus had consistently significant SADIE indices over time at one site, and adult catches could also be linked to larval distributions and counts. It is proposed that observed differences between the two species can be explained by interference between traps and dissimilar movement rates. There was some evidence of an edge effect at the field boundaries.4 The distance between pheromone traps is related to the time that elapses before adjacent traps interfere with trap captures and this limits the detection of statistically significant spatial patterns. It is shown that the current practice of adding trap counts for different Agriotes species and treating them as numerically equivalent is insufficiently robust to be recommended at this stage.5 The implications for the use of sex pheromone traps in wireworm pest management are considered. It is concluded that pheromone traps, as currently used, will not reliably indicate where wireworms occur in a field, and that the complexity of interpreting adult male trap counts limits quantitative predictions of population size.

An essential role for a CD36-related receptor in pheromone detection in Drosophila

The CD36 family of transmembrane receptors is present across metazoans and has been implicated biochemically in lipid binding and transport. Several CD36 proteins function in the immune system as scavenger receptors for bacterial pathogens and seem to act as cofactors for Toll-like receptors by facilitating recognition of bacterially derived lipids. Here we show that a Drosophila melanogaster CD36 homologue, Sensory neuron membrane protein (SNMP), is expressed in a population of olfactory sensory neurons (OSNs) implicated in pheromone detection. SNMP is essential for the electrophysiological responses of OSNs expressing the receptor OR67d to (Z)-11-octadecenyl acetate (cis-vaccenyl acetate, cVA), a volatile male-specific fatty-acid-derived pheromone that regulates sexual and social aggregation behaviours. SNMP is also required for the activation of the moth pheromone receptor HR13 by its lipid-derived pheromone ligand (Z)-11-hexadecenal, but is dispensable for the responses of the conventional odorant receptor OR22a to its short hydrocarbon fruit ester ligands. Finally, we show that SNMP is required for responses of OR67d to cVA when ectopically expressed in OSNs not normally activated by pheromones. Because mammalian CD36 binds fatty acids, we suggest that SNMP acts in concert with odorant receptors to capture pheromone molecules on the surface of olfactory dendrites. Our work identifies an unanticipated cofactor for odorant receptors that is likely to have a widespread role in insect pheromone detection. Moreover, these results define a unifying model for CD36 function, coupling recognition of lipid-based extracellular ligands to signalling receptors in both pheromonal communication and pathogen recognition through the innate immune system.

Ecological functions of volatile organic compounds in aquatic systems

In terrestrial ecosystems, volatile organic compounds (VOCs) are widely acknowledged as an important group of infochemicals. They play a major role in pollinator attraction by terrestrial plants and as insect pheromones. Furthermore, they are the mediating agent of so-called ‘tritrophic interactions’. When plants are attacked by herbivorous insects, volatile signal substances are emitted, which act as attractants for parasitoids that kill the herbivores, thereby protecting the plant from herbivory. Despite the generally acknowledged importance of VOCs in terrestrial chemical ecology, their functions in aquatic food webs are largely unknown. VOCs produced by algae and cyanobacteria are a major concern in water processing, since aquatic primary producers are the reason for regularly encountered taste and odour problems in drinking water. Only very recently, research in aquatic chemical ecology has started to investigate possible ecological functions for the production of VOCs by algae and cyanobacteria. Volatile aldehydes released by wounded cells of marine planktonic diatoms seem to act as defensive compounds against herbivorous copepods on the population level. Just recently, it was found that VOCs released from benthic algae and cyanobacteria can be utilised as food and/or habitat finding cues by aquatic invertebrates such as freshwater gastropods and nematodes. Here, I review concepts and recent experimental studies on the ecological functions of such VOCs in aquatic ecosystems. Understanding the factors that lead to the liberation of volatile compounds is an essential prerequisite to properly assessing their ecological functions. It appears that (similar to terrestrial plant–herbivore interactions) VOCs can also play a steering role for both attraction and defence in aquatic ecosystems.

The Antibacterial Protein Lysozyme Identified as the Termite Egg Recognition Pheromone

Social insects rely heavily on pheromone communication to maintain their sociality. Egg protection is one of the most fundamental social behaviours in social insects. The recent discovery of the termite-egg mimicking fungus ‘termite-ball’ and subsequent studies on termite egg protection behaviour have shown that termites can be manipulated by using the termite egg recognition pheromone (TERP), which strongly evokes the egg-carrying and -grooming behaviours of workers. Despite the great scientific and economic importance, TERP has not been identified because of practical difficulties. Herein we identified the antibacterial protein lysozyme as the TERP. We isolated the target protein using ion-exchange and hydrophobic interaction chromatography, and the MALDI-TOF MS analysis showed a molecular size of 14.5 kDa. We found that the TERP provided antibacterial activity against a gram-positive bacterium. Among the currently known antimicrobial proteins, the molecular size of 14.5 kDa limits the target to lysozyme. Termite lysozymes obtained from eggs and salivary glands, and even hen egg lysozyme, showed a strong termite egg recognition activity. Besides eggs themselves, workers also supply lysozyme to eggs through frequent egg-grooming, by which egg surfaces are coated with saliva containing lysozyme. Reverse transcript PCR analysis showed that mRNA of termite lysozyme was expressed in both salivary glands and eggs. Western blot analysis confirmed that lysozyme production begins in immature eggs in queen ovaries. This is the first identification of proteinaceous pheromone in social insects. Researchers have focused almost exclusively on hydrocarbons when searching for recognition pheromones in social insects. The present finding of a proteinaceous pheromone represents a major step forward in, and result in the broadening of, the search for recognition pheromones. This novel function of lysozyme as a termite pheromone illuminates the profound influence of pathogenic microbes on the evolution of social behaviour in termites.

17.4. Rapid binding, release and inactivation of insect pheromones

17.4. Rapid binding, release and inactivation of insect pheromones