The responses of Tribolium castaneum to wheat germ oil and fungal produced volatiles: Presentation

The red flour beetle Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) is a significant pest affecting a wide variety of different stored products around the Globe. Despite its economic impact, there is evidence that the lures currently used in traps to monitor for this species are largely ineffective. Based on the evolutionary history of T. castaneum, and the ecological niche it occupies, the volatiles of wheat germ oil and volatiles produced by grain-associated fungi have the potential to act as attractants for this species. We used electroantennography (EAG) to measure the electrophysiological response elicited by sixty-eight volatile compounds found in wheat germ oil and/or grain-associated fungi in two T. castaneum strains; an established lab population (CTC12 strain) and a recently caught wild population. Many volatile compounds from both sources elicited strong antennal depolarisations, and the responses of both strains were highly correlated. We then tested whether the compounds that triggered the strongest antennal depolarisations also elicited behavioural responses by using Y-tube olfactometer bioassays and identified several compounds attractive to both strains. The discovery of novel compounds that elicit strong EAG signals and behavioural responses could prove useful in the design of improved lures for T. castaneum and other stored product pests. Our future research will identify how effective these attractive volatiles might be when used in combination, and when used under conditions that more closely replicate a stored product environment.The red flour beetle Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) is a significant pest affecting a wide variety of different stored products around the Globe. Despite its economic impact, there is evidence that the lures currently used in traps to monitor for this species are largely ineffective. Based on the evolutionary history of T. castaneum, and the ecological niche it occupies, the volatiles of wheat germ oil and volatiles produced by grain-associated fungi have the potential to act as attractants for this species. We used electroantennography (EAG) to measure the electrophysiological response elicited by sixty-eight volatile compounds found in wheat germ oil and/or grain-associated fungi in two T. castaneum strains; an established lab population (CTC12 strain) and a recently caught wild population. Many volatile compounds from both sources elicited strong antennal depolarisations, and the responses of both strains were highly correlated. We then tested whether the compounds that triggered the strongest antennal depolarisations also elicited behavioural responses by using Y-tube olfactometer bioassays and identified several compounds attractive to both strains. The discovery of novel compounds that elicit strong EAG signals and behavioural responses could prove useful in the design of improved lures for T. castaneum and other stored product pests. Our future research will identify how effective these attractive volatiles might be when used in combination, and when used under conditions that more closely replicate a stored product environment

Structure elucidation of some insect pheromones : a contribution to the development of selective pest control agents

The use of pheromones is one of the methods currently being investigated intensively as an alternative method of insect control. The various ways in which pheromones might be used in insect control programmes are briefly discussed in Chapter 1.Chapter 2 gives a detailed description of the isolation and identification of the sex pheromone of the American cockroach, Periplaneta americana. The various techniques that have been used for the structure elucidation are described.The sex pheromone of P. americana contains two major components (periplanone-A and periplanone-B), as well as minute amounts of another four.Periplanone-B could be identified as (1 Z, 5 E)-1,10(14)-diepoxy- 4(15), 5-germacradiene-9-one. Periplanone-A proved to be very unstable, isomerizing to a biologically inactive compound. The instability of the compound rendered a complete structure elucidation impossible.The four minor compounds could not be collected in sufficient amounts to carry out a complete structure elucidation.Of the compounds reported to mimic the natural pheromone, only germacrene-D was found to do so. However, its threshold is very much higher than that of the natural pheromone. The same holds for the other reported mimics, even they do elicit electroantennogram responses. Regardless of concentration, none of the mimics elicit responses as marked as the natural pheromone.Apart from causing sexual excitation, periplanone-B also can attract males of P. americana.The isolation, identification and field evaluation of the sex pheromone of the leafroller moth, Archips podana, is described in Chapter 3. The pheromone consists of a mixture of equal amounts of cis -11-tetradecenyl acetate and trans -11-tetradecenyl acetate. Although the individual compounds are not attractive in field experiments, a 1:1 mixture of the two is capable of attracting many males of this species.Investigation of the sex pheromone of the false codling moth, Cryptophlebia leucotreta (Chapters 4 and 5) revealed that the pheromone is a mixture of equal amounts of cis -8-dodecenyl acetate and trans -8-dodecenyl acetate. This finding contradicts other reports which state that the pheromone of this insect is trans -7-dodecenyl acetate. Mixtures of cis -8- and trans -8-dodecenyl acetate in various ratios proved to be very attractive to males of this species.In Chapter 6 the isolation, identification and field evaluation of the sex pheromone of the potato tuberworm moth, Phthorimaea operculella, is described. The sex pheromone of this moth is a mixture of about equal amounts of trans -4, cis -7-tridecadienyl acetate and trans -4, cis -7, cis -10-tridecatrienyl acetate. These findings were confirmed by synthesis and by trapping experiments in the field

Friends and Foes from an Ant Brain's Point of View – Neuronal Correlates of Colony Odors in a Social Insect

Background: Successful cooperation depends on reliable identification of friends and foes. Social insects discriminate colony members (nestmates/friends) from foreign workers (non-nestmates/foes) by colony-specific, multi-component colony odors. Traditionally, complex processing in the brain has been regarded as crucial for colony recognition. Odor information is represented as spatial patterns of activity and processed in the primary olfactory neuropile, the antennal lobe (AL) of insects, which is analogous to the vertebrate olfactory bulb. Correlative evidence indicates that the spatial activity patterns reflect odor-quality, i.e., how an odor is perceived. For colony odors, alternatively, a sensory filter in the peripheral nervous system was suggested, causing specific anosmia to nestmate colony odors. Here, we investigate neuronal correlates of colony odors in the brain of a social insect to directly test whether they are anosmic to nestmate colony odors and whether spatial activity patterns in the AL can predict how odor qualities like ‘‘friend’’ and ‘‘foe’’ are attributed to colony odors. Methodology/Principal Findings: Using ant dummies that mimic natural conditions, we presented colony odors and investigated their neuronal representation in the ant Camponotus floridanus. Nestmate and non-nestmate colony odors elicited neuronal activity: In the periphery, we recorded sensory responses of olfactory receptor neurons (electroantennography), and in the brain, we measured colony odor specific spatial activity patterns in the AL (calcium imaging). Surprisingly, upon repeated stimulation with the same colony odor, spatial activity patterns were variable, and as variable as activity patterns elicited by different colony odors. Conclusions: Ants are not anosmic to nestmate colony odors. However, spatial activity patterns in the AL alone do not provide sufficient information for colony odor discrimination and this finding challenges the current notion of how odor quality is coded. Our result illustrates the enormous challenge for the nervous system to classify multi-component odors and indicates that other neuronal parameters, e.g., precise timing of neuronal activity, are likely necessary for attribution of odor quality to multi-component odors

Development and optimisation of a sex pheromone lure for monitoring populations of saddle gall midge, Haplodiplosis marginata

Saddle gall midge, Haplodiplosis marginata (von Roser) (Diptera: Cecidomyiidae), is a sporadic pest of cereals in Northern and Central Europe and is of increasing importance in the UK. Recently the major component of the sex pheromone produced by adult female H. marginata was reported to be 2-nonyl butyrate. The importance of absolute configuration on attractiveness, the effects on trap catches of the addition of minor pheromone components, dispenser type, and pheromone loading are described in the development of an optimised pheromone lure with which to trap H. marginata males. In analyses of volatiles collected from virgin female H. marginata by gas chromatography (GC) coupled to electroantennographic recording (EAG) from the antenna of a male H. marginata, two EAG responses were observed. Analyses by coupled GC-mass spectrometry (MS) indicated these were due to 2-nonyl butyrate and a trace amount (1%) of 2-heptyl butyrate. A similar trace amount of 2-nonanol was detected in GC-MS analyses but this compound did not elicit an EAG response when the synthetic compound was tested, whereas while the other two compounds did. These three compounds were not observed in collections of volatiles made from male H. marginata. The 2-nonyl butyrate was shown to be the (R)-enantiomer, and i. In field trapping tests (R)-2-nonyl butyrate was at least ten times10× more attractive to male H. marginata than the racemic compound, and while the (S)-enantiomer was unattractive. Addition of the potential minor components individually or together at the naturally -occurring ratios did not increase or reduce the attractiveness of the lure. Polyethylene vials and rubber septa were equally effective as pheromone dispensers, lasting for at least five 5 weeks in the field in the UK, although laboratory tests indicated release from the former was more uniform and more likely to last longer in the field. Increasing loading of pheromone in the dispenser increased attractiveness. Traps baited with polyethylene vials containing 0.5 mg of (R)-2-nonyl butyrate are recommended for monitoring H. marginata and these are far more sensitive than water or sticky traps currently used for monitoring this pest

Wahrnehmung von Wirtsdüften durch Forstschädlinge : Vergleich zwischen einem Holzbrüter und einem Rindenbrüter

The blue pine wood borer (Phaenops cyanea) and the black pine sawyer beetle (Monochamus galloprovincialis) (Fig. 1) both are pests of the white pine (Pinus silvestris) and other Pinus species. Both insects have nearly the same demands regarding their breeding site. Larval development requires a fresh, unwilted inner bark. An infestation occurs on freshly cut trees or on trees suffering from stress (e.g. after dry seasons, loss of needles caused by feeding caterpillars or damage by forest fires). Phaenops cyanea detects susceptible pines by their volatile emissions (SCHÜTZ et al. 2004) and is able to infest the trees already at a low stress level. During feeding the larvae avoid the resin ducts of the tree and thus evade the oleoresin defence. The beetle is endemic in Europe and – under favourable climatic conditions – can cause substantial damage to pine forests. It is the most significant bark-breeding beetle of white pine in the lowlands of north-eastern Germany. Monochamus galloprovincialis is found in Europe and northern Africa. The larvae tend to a more copious feeding which makes them more susceptible to the oleoresin defence of the tree. Thus, M. galloprovincialis prefers trees that are weakened by a higher degree of stress. The economic damage caused by feeding of thebeetle is low. However, the beetle has gained a special attention of forest scientists because of its association with the nematode Bursaphelenchus xylophilus which is causing the pine wilt disease (PWD) in Pinus. The only outbreak of the PWD within Europe is limited to an area of 258.000 ha in Portugal. (MOTA et al. 1999).Die Forstschädlinge Phaenops cyanea (Coleoptera: Buprestidae) und Monochamus galloprovincialis (Coleoptera: Cerambycidae) befallen beide Kiefern (Pinus sylvestris), die geschwächt sind, z.B. durch Wasser-Stress. Die Larven von P. cyanea entwickeln sich in oder unter der Rinde, während Larven von M. galloprovincialis nach einem Fraß im Kambium des befallenen Baumes auch tief in das Holz eindringen. P. cyanea befällt bereits Bäume, die nur einem geringen Stress ausgesetzt waren, während M. galloprovincialis Bäume bevorzugt, die erheblich geschwächt oder bereits tot sind. Die vorliegende Studie soll anhand elektrophysiologischer Experimente untersuchen, welchen olfaktorischen Hinweisen die beiden Insekten bei ihrer Suche nach einem geeigneten Eiablageplatz folgen. Duftstoffe von Pinus sylvestris wurden auf Aktivkohle gesammelt und mit Gaschromatographie, Massenspektroskopie und Elektroantennographie untersucht (GC-MS/ EAD). Die stärksten Signale von P. cyanea traten im Retentionsindex-Bereich von 936 (α-Pinen) bis 1200 auf, wobei insbesondere bizyklische Terpene und Terpenoide wie α-Pinen, β-Pinen, 1,8-Cineol und trans- Verbenol detektiert wurden. M. galloprovincialis reagierte auf einen weiteren Bereich von Stoffen, ebenfalls beginnend mit α-Pinen, bis hin zu Stoffen mit einem Retentionsindex von ca. 1300. Es scheint eine spezifische Empfindlichkeit für monozyklische und azyklische Terpene und Terpenoide vorzuliegen, insbesondere für γ-Terpinen, Terpinolen, β-Myrcen und p-Cymen

A carboxylesterase, Esterase-6, modulates sensory physiological and behavioral response dynamics to pheromone in Drosophila

Conclusions: Our study presents evidence that Est-6 plays a role in the physiological and behavioral dynamics of sex pheromone response in Drosophila males and supports a role of Est-6 as an odorant-degrading enzyme (ODE) in male antennae. Our results also expand the role of Est-6 in Drosophila biology, from reproduction to olfaction, and highlight the role of ODEs in insect olfaction

Odor Compound Detection in Male Euglossine Bees

Male euglossine bees collect fragrances from various sources, which they store and use for as yet unknown purposes. They are attracted, often specifically, to single odor compounds and blends thereof. We used gas chromatography with electroantennographic detection (GC-EAD) and electroantennography (EAG) to investigate the response to 8 odor compounds by males of two euglossine species, Euglossa cybelia Moure and Eulaema polychroma (Mocsàry). In E. cybelia, we recorded EAD reactions in response to 1,8-cineole, methyl benzoate, benzyl actetate, methyl salicylate, eugenbl, and methyl cinnamate. E. polychroma responded to the same compounds in EAG experiments, while (ls)(-)α-pinene and β-pinene failed to trigger EAD or EAG responses in the bees. Blends of two compounds triggered larger responses than single compounds in EAG experiments with E. polychroma, however, when α-pinene was added, reactions decreased. In the light of existing data on the bees' behavior towards these odor compounds, our work indicates that both peripheral and central nervous processes influence the attraction of euglossine bees to odor

A multimodal approach for tracing lateralization along the olfactory pathway in the honeybee through electrophysiological recordings, morpho-functional imaging, and behavioural studies

Recent studies have revealed asymmetries between the left and right sides of the brain in invertebrate species. Here we present a review of a series of recent studies from our labs, aimed at tracing asymmetries at different stages along the honeybee's (Apis mellifera) olfactory pathway. These include estimates of the number of sensilla present on the two antennae, obtained by scanning electron microscopy, as well as electroantennography recordings of the left and right antennal responses to odorants. We describe investigative studies of the antennal lobes, where multi-photon microscopy is used to search for possible morphological asymmetries between the two brain sides. Moreover, we report on recently published results obtained by two-photon calcium imaging for functional mapping of the antennal lobe aimed at comparing patterns of activity evoked by different odours. Finally, possible links to the results of behavioural tests, measuring asymmetries in single-sided olfactory memory recall, are discussed.Comment: 28 pages, 8 figure

Indication of bioactive candidates among body volatiles of gregarious adult locusts Locusta migratoria manilensis by electroantennography (EAG) test

Gregarious adult locusts are believed to release many bioactive volatiles from their bodies for the mediation of their biological characteristics. The determination of these bioactive body volatiles can contribute to the development of new, environmentally benign methods of locust control. An important locust, Locusta migratoria manilensis is an extremely destructive agricultural pest in China. Body volatiles of gregarious L. m. manilensis adults were found to be involved in mediation of aggregation behavior, but bioactive components in the body volatiles had not been indicated. In this study, four compounds were identified from body volatiles of gregarious L. m. manilensis adults using gas chromatography-mass spectrometry analysis: 2-hexanone, butyl acetate and α-pinene from both sexes and 2-heptanone from males only. The electroantennography (EAG) test indicated that gregarious adult males and females had the same EAG response pattern to these compounds. 2-Hexanone, 2-heptanone and butyl acetate elicited dose-dependent responses, which are considered as bioactive candidates among body volatiles. The two ketones, 2-hexanone and 2-heptanone, were the strongest olfactory stimuli for gregarious L. m. manilensis adults. The contribution of these EAG-active compounds to the mediation of aggregation or other behaviors still remains to be further investigated.Key words: Locusta migratoria manilensis, body volatiles, GC-MS, EAG, bioactive compounds