Chemical signatures affecting host choice in the Eucalyptus herbivore,Gonipterus sp. (Curculionidae: Coleoptera)

It is well known that herbivorous insects respond to host plant volatiles. Yet details of how these insects perceive the complex profile of volatiles from different potential host plants have not been studied for most insects. Gonipterus spp. are important pests of Eucalyptus worldwide, but differ in their preference for different species of this host. In this study, we consider whether host volatiles affect the host choice for a Gonipterus sp. and we characterize the response of the female insect to the volatile profiles from these hosts in an electro-antennographic experiment. We sampled volatiles from freshly damaged leaves of three Eucalyptus species and analysed the profiles by gas chromatography coupled to electro-antennography (GC-EAD) and gas chromatography coupled to mass spectrometry. Female weevils gave a mixed range of electro-physiological responses to volatile puffs from leaves of different tree species. This suggests that differences in volatile profiles of different trees play a role in how these beetles discriminate between potential hosts. GC-EAD analysis showed that responses were as complex as the volatile chemical compositions of the leaves. A number of these chemicals were identified, and responses were mostly due to general green leaf volatiles. This was also evident from the fact that the insects showed a markedly greater response to the total volatile profile from freshly damaged leaves for all species. The females of the Gonipterus sp. can therefore detect damaged leaves, which may indicate host quality. Host specificity information is further expected to lie in the relative differences in emission ratios and synergism between different host chemical compounds, rather than specific individual compounds.     

Aquatic insects of the Neman River and its tributaries

The aquatic insects of the Neman River and its tributaries were studied. 178 species belonging to 9 orders were found: Collembola—2 species, Ephemeroptera—33, Odonata—16, Plecoptera—10, Heteroptera—20, Coleoptera—39, Megaloptera—2, Trichoptera—54, and Lepidoptera—2 species. Two species of aquatic insects new for the Belarusian fauna were found, Pomatinus substriatus (Ph. Müller, 1806) (Coleoptera) and Brachycercus europaeus Kluge, 1991 (Ephemeroptera).     

Antennal olfactory sensory neurones responsive to host and nonhost plant volatiles in gorse pod moth Cydia succedana

We investigate the response profiles of the antennal olfactory sensory neurones (OSNs) in male and female gorse pod moth Cydia succedana to host and nonhost volatiles, using the single sensillum recording technique. Eight different classes of olfactory sensilla are identified in female C. succedana and five different classes of olfactory sensilla in males. Nineteen different classes of OSNs are identified from the sensilla in females, and nine different classes of OSNs in the male sensilla. All classes of sensilla, except class F7 and class M1 sensilla, co‐compartmentalize two or three OSNs in each sensillum, and the OSNs present in the same sensillum are specialized for different volatiles. Most plant‐volatile OSNs exhibit phasic‐tonic type of temporal responses, whereas the pheromone OSNs in male C. succedana show rather phasic responses. The majority of OSNs identified in C. succedana display highly specialized responses to a narrow range of volatiles, whereas only a small proportion of OSNs show broad response spectra. Two most abundant classes of OSNs exhibit highly specialized responses to β‐myrcene and (E)‐β‐ocimene, two major volatiles released by gorse (Ulex europaeus), the main host of C. succedana. By contrast, several other classes of OSNs exhibit highly specialized responses to geraniol, (Z)‐3‐hexen‐1‐ol, (±)‐α‐terpineol, citral and benzyl acetate, which are produced by various nonhost plants. Taking the results of the present study together, we suggest that C. succedana use the combinational input from a set of highly specialized OSNs for host plant volatiles and another set of highly specialized OSNs for nonhost volatiles to discriminate between hosts and nonhosts.     

Diversity of Odonata (Insecta) from Dholbaha Dam (Distt. Hoshiarpur) in Punjab Shivalik,India

Study on the species diversity of the order Odonata was carried out during 2002 ∼ 2004 at Dholbaha dam, which has a moist deciduous forest surrounding it in district Hoshiarpur, Punjab, India. A total of 30 species belonging to 7 families of order Odonata were recorded during the study period. The family Libellulidae, represented by 18 species was the most dominant followed by Coenagrionidae (6 species), Aeshnidae (2 species) and Calopterygidae, Chlorocyphidae, Euphaeidae and Gomphidae each having 1 species. In terms of total number of individuals, family Libellulidae constituted maximum with 64.36% followed by Coenagrionidae (28.50%), Chlorocyphidae (1.83%), Gomphidae (1.62%), Euphaeidae (1.56%), Calopterygidae (1.38%) and Aeshnidae (0.75%). Pantala flavescens (Fabricius), a migratory species was the most dominant in number of individuals constituting 17.12% of the total. The least dominant species included Anax immaculifrons Rambur (0.38%) and Anax parthenope parthenope (Selys) (0.36%). Shannon-Wiener index of species diversity of Odonata was 2.988 and 3.029 during 2002–2003 and 2003–2004, respectively. Seven new species have also been reported from the Dholbaha dam during this study period thus increasing the total species number of odonates so far recorded from this area from 29 to 36.     

Single Sensillum Recordings in the Insects Drosophila melanogaster and Anopheles gambiae

The sense of smell is essential for insects to find foods, mates, predators, and oviposition sites³. Insect olfactory sensory neurons (OSNs) are enclosed in sensory hairs called sensilla, which cover the surface of olfactory organs. The surface of each sensillum is covered with tiny pores, through which odorants pass and dissolve in a fluid called sensillum lymph, which bathes the sensory dendrites of the OSNs housed in a given sensillum. The OSN dendrites express odorant receptor (OR) proteins, which in insects function as odor-gated ion channels^{4, 5}. The interaction of odorants with ORs either increases or decreases the basal firing rate of the OSN. This neuronal activity in the form of action potentials embodies the first representation of the quality, intensity, and temporal characteristics of the odorant^{6, 7}.Given the easy access to these sensory hairs, it is possible to perform extracellular recordings from single OSNs by introducing a recording electrode into the sensillum lymph, while the reference electrode is placed in the lymph of the eye or body of the insect. In Drosophila, sensilla house between one and four OSNs, but each OSN typically displays a characteristic spike amplitude. Spike sorting techniques make it possible to assign spiking responses to individual OSNs. This single sensillum recording (SSR) technique monitors the difference in potential between the sensillum lymph and the reference electrode as electrical spikes that are generated by the receptor activity on OSNs^{1, 2, 8}. Changes in the number of spikes in response to the odorant represent the cellular basis of odor coding in insects. Here, we describe the preparation method currently used in our lab to perform SSR on Drosophila melanogaster and Anopheles gambiae, and show representative traces induced by the odorants in a sensillum-specific manner.Open in a separate windowClick here to view.^{(78M, flv)}     

Antimicrobial peptides isolated from insects and their potential applications

Antimicrobial peptides (AMPs) in insects have the potential to be developed as chemotherapy agents against numerous microbial species. This article reviewed the existing knowledge of what have been focused so far on published materials related to AMPs isolated from insects. Previous studies were focused on peptide characterization and the mechanism pathways of different AMPs from a variety of insect Orders. Most studied insect Orders are as follows: Hymenoptera (50%), Diptera (17%), Coleoptera (13%), Lepidoptera (10%), Hemiptera (5%), Blattodea (3%) and Odonata (2%). Dozens of new AMPs have been extracted from insects recently. However, more studies in vivo and in vitro are necessary to fully understand their effect and the mechanisms of antimicrobial action to utilize their promising potential in cosmetic and pharmaceutical industries.     

Temperature Effect on the Development of Tropical Dragonfly Eggs

Physiological constraints in insects are related to several large-scale processes such as species distribution and thermal adaptation. Here, we fill an important gap in ecophysiology knowledge by accessing the relationship between temperature and embrionary development time in four dragonfly species. We evaluated two questions (1) what is the effect of temperature on the development time of Odonata eggs, and (2) considering a degree-day relationship, could a simple linear model describe the dependence of embrionary development time on temperature or it is better described by a more complex non-linear relation. Egg development time of Erythrodiplax fusca (Rambur), Micrathyria hesperis Ris, Perithemis mooma Kirby, and Miathyria simplex (Rambur) (Odonata: Libellulidae) were evaluated. We put the eggs at different temperatures (15, 20, 25, and 30°C) and counted the number of hatched larvae daily. A nonlinear response of the development to the temperature was found, differing from the expected pattern for standard degree-day analysis. Furthermore, we observed that there is a similar process in the development time and hatching synchronization between species, with all species presenting faster egg development at high temperatures. Species-specific differences are more evident at lower temperatures (15°C), with no egg development in M. simplex. Only E. fusca was relatively insensitive to temperature changes with similar hatching rates in all treatments.     

A broadly tuned odorant receptor in neurons of trichoid sensilla in locust,Locusta migratoria

Insects have evolved sophisticated olfactory reception systems to sense exogenous chemical signals. Odorant receptors (ORs) on the membrane of chemosensory neurons are believed to be key molecules in sensing exogenous chemical cues. ORs in different species of insects are diverse and should tune a species to its own specific semiochemicals relevant to their survival. The orthopteran insect, locust (Locusta migratoria), is a model hemimetabolous insect. There is very limited knowledge on the functions of locust ORs although many locust OR genes have been identified in genomic sequencing experiments. In this paper, a locust OR, LmigOR3 was localized to neurons housed in trichoid sensilla by in situ hybridization. LmigOR3 was expressed as a transgene in Drosophila trichoid olfactory neurons (aT1) lacking the endogenous receptor Or67d and the olfactory tuning curve and dose-response curves were established for this locust receptor. The results show that LmigOR3 sensitizes neurons to ketones, esters and heterocyclic compounds, indicating that LmigOR3 is a broadly tuned receptor. LmigOR3 is the first odorant receptor from Orthoptera that has been functionally analyzed in the Drosophila aT1 system. This work demonstrates the utility of the Drosophila aT1 system for functional analysis of locust odorant receptors and suggests that LmigOR3 may be involved in detecting food odorants, or perhaps locust body volatiles that may help us to develop new control methods for locusts.     

A critical overview of progress in studies of migration of dragonflies (Odonata: Anisoptera), with emphasis on North America

Migration by Odonata has been recorded sporadically for several centuries, but only recently have new technologies and a new wave of interest in these ancient insects sparked a concerted effort to understand the extent, behavioral mechanisms, adaptive significance, and ecological consequences of this phenomenon. Here I review our current knowledge of these sometimes spectacular flights, focusing on the few species in North America that are known to migrate more or less annually. One of these, the Common Green Darner, Anax junius, has been shown to traverse hundreds to thousands of kilometers from north to south during fall migration. Pantala flavescens (Wandering Glider) is plausibly inferred to make an overseas flight from India to East Africa with the Northeast Monsoon, although its migrations in North America are less well understood. Large scale movements of these and other species raises questions about population connectivity, ecosystem impacts, the nature and evolution of cues that initiate migration, and effects of climate change on these phenomena.     

Incidence of Wolbachia in aquatic insects

Wolbachia is a genus of intracellular bacteria typically found within the reproductive systems of insects that manipulates those systems of their hosts. While current estimates of Wolbachia incidence suggest that it infects approximately half of all arthropod species, these estimates are based almost entirely on terrestrial insects. No systematic survey of Wolbachia in aquatic insects has been performed. To estimate Wolbachia incidence among aquatic insect species, we combined field‐collected samples from the Missouri River (251 samples from 58 species) with a global database from previously published surveys. The final database contained 5,598 samples of 2,687 total species (228 aquatic and 2,459 terrestrial). We estimate that 52% (95% CrIs: 44%–60%) of aquatic insect species carry Wolbachia, compared to 60% (58%–63%) of terrestrial insects. Among aquatic insects, infected orders included Odonata, Coleoptera, Trichoptera, Ephemeroptera, Diptera, Hemiptera, and Plecoptera. Incidence was highest within aquatic Diptera and Hemiptera (69%), Odonata (50%), and Coleoptera (53%), and was lowest within Ephemeroptera (13%). These results indicate that Wolbachia is common among aquatic insects, but incidence varies widely across orders and is especially uncertain in those orders with low sample sizes such as Ephemeroptera, Plecoptera, and Trichoptera.     

Chemical diversity of floral volatiles in Asclepiadoideae-Asclepiadeae (Apocynaceae)

Floral volatiles of 15 plant species from 8 genera (Cynanchum, Funastrum, Gonolobus, Metastelma, Oxypetalum, Orthosia, Sarcostemma, and Vincetoxicum) of the Apocynaceae-Asclepiadoideae tribe Asclepiadeae were investigated to get a better understanding of the odor chemistry, and of the role of odors in pollinator attraction. Floral volatiles were collected via headspace adsorption and analysed by GC–MS (gas chromatography–mass spectrometry). Of the 170 volatile compounds detected, 128 were identified, most of which are widespread floral scent compounds known from many different plant species. The species can be divided into two main groups: (1) species dominated by monoterpenoids (linalool, Z/E-ocimene), and (2) species dominated by benzenoids (benzaldehyde, phenylacetaldehyde, 2-phenylethyl acetate). Species of both chemotypes are pollinated mainly by Hymenoptera and Lepidoptera, and possibly these insects are effectively attracted by both monoterpenoids and benzenoids; alternatively, benzenoid-dominated plant species might attract a different subset of pollinators than the monoterpenoid-dominated plants.     

Wildflower-pollinator interactions: Which phytochemicals are involved?

The intensification of agricultural practices contributes to the decline of many taxa, such as insects and weeds. Wildflower species have an important environmental impact on rural biodiversity since plant-pollinator networks play a key role in both landscape aesthetics and environmental functionality. Due to their scarcity and/or disappearance in conventional agroecosystems, wildflowers are now being used in strips to restore the agro-environment.In this study, fifteen wildflower species were sown in order to verify their ecological performance in terms of a plant-pollinator interaction while in laboratory the several chemicals emitted by the flowers were identified. Flowering periods were concentrated in the spring, although flowering periods extended to the hot and dry summer months in some species. An extreme variability was found in terms of quantitative and qualitative pollinator-attractiveness (i.e., bees, bumblebees, hoverfly, bee flies and butterflies). Most wildflower species emit a volatiles belonging above all to one of the several chemical classes. A hierarchical cluster analysis of the different volatile emissions did not fully correlate with the botanical taxa of the respectives wildflowers. Often, single chemical compounds prevailed, such as β-ocimene and limonene among monoterpenes hydrocarbons, santolina alcohol in the case of oxygenated monoterpenes, or (Z)- or (E)-3-hexenol acetate for non-terpenes derivatives. It is believed that these chemical compounds can play an ecological role in plant-pollinator food webs. The hypothesis that the chemistry of the volatiles implies a specialized plant-pollinator co-evolution was confirmed by a significant regression (p < 0.05), which showed an inverse relationship between chemical diversity (H’) and pollinator dominance (D) indexes. The chemical specificity indicates the specificity of pollinators and vice versa.     

The antennae of damselfly larvae

The larval antennal sensilla of two Zygoptera species, Calopteryx haemorroidalis (Calopterygidae) and Ischnura elegans (Coenagrionidae) are investigated with SEM and TEM. These two species have different antennae (geniculate, setaceous) and live in different environments (lotic, lentic waters). Notwithstanding this, similarities in the kind and distribution of sensilla are outlined: in both species the majority of sensilla types is located on the apical portion of the antenna, namely a composed coeloconic sensillum (possible chemoreceptor), two other coeloconic sensilla (possible thermo-hygroreceptors) and an apical seta (direct contact mechanoreceptor). Other mechanoreceptors, such as filiform hairs sensitive to movements of the surrounding medium or bristles positioned to sense the movements of the flagellar segments, are present on the antenna. Similarities in the antennal sensilla types and distribution are observed also with other dragonfly species, such as Onychogomphus forcipatus and Libellula depressa. A peculiar structure with an internal organization similar to that of a gland is observed in the apical antenna of C. haemorroidalis and I. elegans and it is present also in O. forcipatus and L. depressa. The possible function of this structure is at the moment unknown but deserves further investigations owing to its widespread presence in Odonata larvae.     

Floral scent composition in early diverging taxa of Asclepiadoideae,and Secamonoideae (Apocynaceae)

The Apocynaceae–Asclepiadoideae are well known for their specialized floral morphologies and pollination systems and many species have distinct floral aromas. However, our knowledge on the chemistry of floral volatiles in this plant family is relatively limited although it has been suspected that floral scent plays a key function for pollinator attraction. This is the third paper in a series of papers reporting on the floral odours of Asclepiadoideae. Floral odours of eleven species from seven genera (Cibirhiza, Fockea, Gymnema, Hoya, Marsdenia, Stephanotis and Telosma) of early diverging taxa of Apocynaceae–Asclepiadoideae, and two species of Secamone (Apocynaceae–Secamonoideae) were collected using headspace sampling and then analyzed via GC–MS. We detected 151 compounds, of which 103 were identified. The vast majority of chemicals identified are common components in flower odour bouquets of angiosperms. However, striking was the high relative amount of acetoin (97.6%) in the flower scent of Cibirhiza albersiana. This compound has rarely been reported as a flower scent component and is more commonly found in fermentation odours. Bray–Curtis similarities and Nonmetric-Multidiminsional Scaling (NMDS) analyses showed that each of the species has a distinct odour pattern. This is mostly due to only twelve compounds which singly or in different combinations dominated the scent of the species: the benzenoids benzyl acetate, benzaldehyde, methyl benzoate, and 2-phenylethyl alcohol; the monoterpenoids (E)-ocimene, (Z)-ocimene, linalool, and eucalyptol; and the aliphatic compounds acetoin, and (E,Z)-2,6-nonadienal. The floral scent compositions are discussed in relation to tribal affiliations and their potential role for pollinator attraction, and are compared with the scent data available from other Asclepiadoideae species.     

The efficacy of DNA barcoding in the classification,genetic differentiation,and biodiversity assessment of benthic macroinvertebrates

Macroinvertebrates have been recognized as key ecological indicators of aquatic environment and are the most commonly used approaches for water quality assessment. However, species identification of macroinvertebrates (especially of aquatic insects) proves to be very difficult due to the lack of taxonomic expertise in some regions and can become time‐consuming. In this study, we evaluated the feasibility of DNA barcoding for the classification of benthic macroinvertebrates and investigated the genetic differentiation in seven orders (Insecta: Ephemeroptera, Plecoptera, Trichoptera, Diptera, Hemiptera, Coleoptera, and Odonata) from four large transboundary rivers of northwest China and further explored its potential application to biodiversity assessment. A total of 1,144 COI sequences, belonging to 176 species, 112 genera, and 53 families were obtained and analyzed. The barcoding gap analysis showed that COI gene fragment yielded significant intra‐ and interspecific divergences and obvious barcoding gaps. NJ phylogenetic trees showed that all species group into monophyletic species clusters whether from the same population or not, except two species (Polypedilum. laetum and Polypedilum. bullum). The distance‐based (ABGD) and tree‐based (PTP and MPTP) methods were utilized for grouping specimens into Operational Taxonomic Units (OTUs) and delimiting species. The ABGD, PTP, and MPTP analysis were divided into 177 (p = .0599), 197, and 195 OTUs, respectively. The BIN analysis generated 186 different BINs. Overall, our study showed that DNA barcoding offers an effective framework for macroinvertebrate species identification and sheds new light on the biodiversity assessment of local macroinvertebrates. Also, the construction of DNA barcode reference library of benthic macroinvertebrates in Eurasian transboundary rivers provides a solid backup for bioassessment studies of freshwater habitats using modern high‐throughput technologies in the near future.     

Volatile compounds from Liposcelis bostrychophila (Psocoptera: Liposcelididae) and their environment and their effects on settling behaviour

Headspace from above either Liposcelis bostrychophila Badonnel reared on powdered food; insects without food or from powdered food only were collected on five occasions over a period of four weeks. Volatiles were analysed by thermal desorption gas chromatography-mass spectrometry (TD-GCMS) to look for ecologically significant volatile compounds. Hexanoic acid (HA) was the major compound in the insect only and diet only volatiles (insect 25.6 ± 1.6%, diet 32.9 ± 1.13%). Isobutyric acid was the main compound detected in the volatiles from both insects and diet (35.3 ± 6%). Butyric acid (BA) and acetoin (HB) were also present at >2% of the total peak areas. HB was not detected in the insect only volatiles. Bioassays showed that hexanoic acid was the most repellent chemical. Mixtures of compounds representing the proportions of HA, BA, IBA, and HB in the volatiles did not have any prolonged effect on settling or selection by booklice in a two choice bioassay. L. bostrychophila can avoid individual volatile chemicals but the effects can be masked when they are incorporated into mixtures. As some volatile compounds can be detected by booklice they may govern dispersal, but further work is required to clarify their significance.     

The importance of root-produced volatiles as foraging cues for entomopathogenic nematodes

Background

Entomopathogenic nematodes (EPNs) are tiny parasitic worms that parasitize insects, in which they reproduce. Their foraging behavior has been subject to numerous studies, most of which have proposed that, at short distances, EPNs use chemicals that are emitted directly from the host as host location cues. Carbon dioxide (CO₂) in particular has been implicated as an important cue. Recent evidence shows that at longer distances several EPNs take advantage of volatiles that are specifically emitted by roots in response to insect attack. Studies that have revealed these plant-mediated interactions among three trophic levels have been met with some disbelief.

Scope

This review aims to take away this skepticism by summarizing the evidence for a role of root volatiles as foraging cues for EPNs. To reinforce our argument, we conducted olfactometer assays in which we directly compared the attraction of an EPN species to CO₂ and two typical inducible root volatiles.

Conclusions

The combination of the ubiquitous gas and a more specific root volatile was found to be considerably more attractive than one of the two alone. Hence, future studies on EPN foraging behavior should take into account that CO₂ and plant volatiles may work in synergy as attractants for EPNs. Recent research efforts also reveal prospects of exploiting plant-produced signals to improve the biological control of insect pests in the rhizosphere.     

Identification of linalool produced by two species of bark beetles of the genus Ips

The terpene alcohol linalool (3,7-dimethyl-1,6-octadien-3-ol) has been isolated from volatiles produced by Ips paraconfusus females and from frass produced by I. pini males, both insects boring in ponderosa pine. Neither species of either sex responds to linalool in the laboratory bioassay. Pitfalls involved in identification of some terpene alcohols are noted.     

Volatiles from host plant brinjal attract the brinjal Fruit and Shoot Borer -Leucinodes orbonalis Guenee

Brinjal Fruit and Shoot Borer- Leucinodes orbonalis Guenee is a major insect pest on brinjal- Solanum melongena worldwide. An effective strategy used in developing pest controlling agents is the synergism between insect pheromones and host plant volatiles, which can increase the attraction of insect pest. The present study was aimed at investigating the chemical constituents and attractant effects of the volatiles extracted from different parts of the host plant brinjal on the behavior of adult L. orbonalis. Bioassay using Y-shaped olfactometer revealed that the one-day old virgin female, gravid female and male insects respond positively to the host plant volatiles extracted from fruits, leaves and shoots but not to that of flowers. It was shown that the gravid females were significantly attracted to all three volatiles (p < 0.05). Bioassay using X-shaped olfactometer identified that all three types of insects highly preferred the volatiles from fruits (p < 0.05). Gas chromatography-mass spectrometry analysis of volatiles indicated that brinjal plant produces volatile secondary metabolites, which include 2,2′-(Ethane-1,2-diylbis(oxy))bis(ethane-2,1-diyl) dibenzoate (12.11%), 3,7-dimethylocta-1,6-dien-3-ol (22.38%), Benzyl alcohol (22.9%) and Benzyl alcohol (27.06%) as major constituents from fruits, shoots, leaves and flowers respectively. Responses of insects to the volatiles from host plant in the absence of visual cues direct us to focus on the importance of host plant volatiles to locate the plant. Results of this study emphasize the major role that host plant volatiles play in the attraction of insect pests towards the plant.