Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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The response specificity of Trichogramma egg parasitoids towards infochemicals during host location
Fatouros, N.E. ; Bukovinszkine-Kiss, G. ; Dicke, M. ; Hilker, M. - \ 2007
Journal of Insect Behavior 20 (2007)1. - ISSN 0892-7553 - p. 53 - 65.
pieris-brassicae l - evanescens westwood - behavioral variations - mamestra-brassicae - biological-control - strains - hymenoptera - oviposition - lepidoptera - kairomones
Parasitoids are confronted with many different infochemicals of their hosts and food plants during host selection. Here, we investigated the effect of kairomones from the adult host Pieris brassicae and of cues present on Brussels sprout plants infested by P. brassicae eggs on the behavioral response of the egg parasitoid Trichogramma evanescens. Additionally, we tested whether the parasitoid¿s acceptance of P. brassicae eggs changes with different host ages. The wasps did not discriminate between olfactory cues from mated and virgin females or between mated females and males of P. brassicae. T. evanescens randomly climbed on the butterflies, showing a phoretic behavior without any preference for a certain sex. The parasitoid was arrested on leaf parts next to 1-day-old host egg masses. This arrestment might be due to cues deposited during oviposition. The wasps parasitized host eggs up to 3 days old equally well. Our results were compared with former studies on responses by T .brassicae showing that T. evanescens makes less use of infochemicals from P. brassicae than T. brassicae.
Chemical ecology and integrated management of the banana weevil Cosmopolites sordidus in Uganda
Tinzaara, W. - \ 2005
Wageningen University. Promotor(en): Marcel Dicke; Arnold van Huis, co-promotor(en): C.S. Gold. - [S.l.] : S.n. - ISBN 9085041767 - 184
insectenplagen - cosmopolites sordidus - chemische ecologie - geïntegreerde plagenbestrijding - feromonen - kairomonen - musa - bananen - biologische bestrijding - bananas - insect pests - chemical ecology - pheromones - kairomones - integrated pest management - biological control
Constitutive and herbivore-induced volatiles in pear, alder and hawthorn trees
Scutareanu, P. ; Bruin, J. de; Posthumus, M.A. ; Drukker, B. - \ 2003
Chemoecology 13 (2003). - ISSN 0937-7409 - p. 63 - 74.
induced plant volatiles - anthocorid predators - natural enemies - identification - host - semiochemicals - populations - kairomones - responses - defense
Qualitative and quantitative differences among pear cultivars were found in constitutive and Cacopsylla-induced volatiles, depending on experimental treatment of the trees (i.e., uninfested and partly or completely infested by psyllids). Blend differences were also found between pear cultivars and wild-type pear, alder and hawthorn-the latter trees are frequently present in pear orchard hedgerows. Interesting differences were found in the presence of methyl salicylate and (E,E)-alpha-farnesene, two compounds previously found to mediate attraction of predatory bugs towards psyllid-infested pear trees. Methyl salicylate is expressed constitutively and is induced systemically by infestation in the whole plant of all four cultivars. (E,E)-alpha-farnesene on the other hand showed also systemic induction in Bartlett, NY10355 and Beurre Hardy, but in partially infested Conference trees it was induced locally, only in herbivore-damaged leaves. No methyl salicylate or (E,E)-alpha-farnesene were identified in honeydew. In field collected headspace samples of alder leaves infested by aphids and leaf beetles we found methyl salicylate but no (E,E)-alpha-farnesene, whereas in uninfested hawthorn neither were identified. Insight in the variability of damage-related pear volatiles will have important implications for integrated pest management in the field.
Increased risk of parasitism as ecological costs of using aggregation pheromones: laboratory and field study of Drosophila-Leptopilina interaction
Wertheim, B. ; Vet, L.E.M. ; Dicke, M. - \ 2003
Oikos 100 (2003)2. - ISSN 0030-1299 - p. 269 - 282.
reliability-detectability problem - heterotoma thomson hymenoptera - foraging behavior - host location - melanogaster - exploitation - eucoilidae - information - generalist - kairomones
Information conveyance plays an important role in parasitoid-host interactions. Several sources of information are available for searching parasitoids and exploitation of that information during the different phases of host location depends on its reliability, detectability and accuracy. One source of information especially suitable for exploitation by parasitoids is a host aggregation pheromone, because this often combines all three aspects. In laboratory and field experiments we studied the behavioural responses of the parasitoid Leptopilina heterotoma to the aggregation pheromone of the fruit fly Drosophila melanogaster, both for substrate selection and the behaviour on host snbstrates. Our results show that substrates with increasing dose of the host's aggregation pheromone attract increasingly more parasitoids, whereas we found no significant effects of pheromone on parasitoid searching behaviour on the substrates. Parasitoid searching behaviour on substrates was influenced by other host cues (e.g. larval exerements, traces of adults other than aggregation pheromone), which is discussed in relation to the expectations from reliability-detectability theory. The responses of the parasitoids were further influenced by substrate quality (i.e. yeast concentration) and the microscale distribution of pheromone. In several field experiments, the fraction of fruit fly larvae that was parasitised was significantly higher in substrates with aggregation pheromone than in control substrates, indicating an ecological cost to the use of aggregation pheromones in adult D. melanogaster.
Olfaction in the malaria mosquito Anopheles gambiae : electrophysiology and identification of kairomones
Meijerink, J. - \ 1999
Agricultural University. Promotor(en): Joop van Lenteren; Joop van Loon. - S.l. : S.n. - ISBN 9789058081179 - 139
anopheles gambiae - reuk - kairomonen - elektrofysiologie - identificatie - smell - kairomones - electrophysiology - identification
<p>Female mosquitoes of the species <em>Anopheles gambiae</em> Giles <em>sensu stricto</em> are important vectors of human malaria in Africa. It is generally assumed that they locate their human host by odours. These odours are detected by olfactory receptor neurons situated within cuticular extensions on the antenna. These cuticular extensions, called sensilla, contain numerous pores through which the odours can enter the sensillum and reach the olfactory receptor neuron membrane. Despite the fact that these mosquitoes are so important for the transmission of malaria, hardly any sensory studies have been performed to date. Therefore, the goal of this study was to analyze the response spectra and characteristics of the olfactory receptor neurons encoding human-derived odours in female <em>An. gambiae</em> . Another goal of this study was the identification of human odours which guide female <em>An. gambiae</em> to its host. This was accomplished by making chemical analyses of the odour profile of human sweat.<p>Firstly, a scanning electron microscopic (SEM) study was undertaken to identify the different types of sensilla exhibited on the antennae of female <em>An. gambiae</em> . Chapter 2 shows SEM photographs of the six different types of antennal sensilla: large and small sensilla coeloconica, grooved peg sensilla, sensilla trichodea, sensilla ampullacea and sensilla chaetica. The distribution of the different sensilla on the thirteen segments is tentatively described. Odours present on the human skin or identified in the headspace of human sweat evoked responses of grooved peg- and sensilla trichodea receptor neurons (chapter 4 and 6). Although the grooved peg sensillum is easily recognized during SEM studies and light microscopic observations, the different subtypes of sensilla trichodea are hard to distinguish in <em>An. gambiae</em> . SEM photographs of two different types of sensilla trichodea housing receptor neurons responsive to sweat-borne components are shown in chapter 2.<p>The antennal olfactory responses of female <em>An. gambiae</em> were studied by means of electroantennography (chapter 3). The electroantennogram (EAG) is considered to be the summed activity of all (or a part of the) responsive sensory receptor neurons on the antenna. Initially, the technical aspects of the EAG recording technique were closely examined. It was found that when using tungsten electrodes, artefactual electrode potentials were generated by the carboxylic acids, propionic acid, butyric acid and hexanoic acid. No artefactual electrode potentials were obtained with glass electrodes. A blend of carboxylic acids has been reported to be attractive for female <em>An. gambiae</em> mosquitoes. These are present on the human skin where they display an enormous diversity in chemical structure. To quantify the antennal olfactory sensitivity to carboxylic acids, EAG studies were conducted with glass electrodes. Carboxylic acids with carbon chain lengths of 5-8 (C <sub>5</sub> -C <sub>8</sub> )elicited high EAG amplitudes, while lower responses were evoked by the less volatile acids, C <sub>9</sub> -C <sub>14</sub> . Hexanoic acid evoked the highest EAG response.<p>Single sensillum studies were undertaken to reveal antennal olfactory receptor neurons responsive to carboxylic acids (chapter 4). Neurons innervating one or two of the morphologically different subtypes sensilla trichodea were found to respond to the short chain carboxylic acids: acetic acid (C <sub>2</sub> ), propionic acid (C <sub>3</sub> ), butyric acid (C <sub>4</sub> ), iso-butyric acid (iC <sub>4</sub> ) and iso-valeric acid (iC <sub>5</sub> ). Usually the receptor neurons responded by inhibition, but receptor neurons were also found responding by excitation to the short chain carboxylic acids. Occasionally receptor neurons were found which responded by excitation to 1-octen-3-ol. Dose-response characteristics were assessed for the carboxylic acid-inhibited cell type. It was demonstrated that the carboxylic acid-inhibited neuron was equally sensitive to the short chain acids tested. This was revealed by making corrections for the differences in volatility of the different short chain acids. It is suggested that in this case an inhibitory response might function to block the response of a specialised cell normally responding by excitation to other stimuli (chapter 7).<p>Because behavioural studies indicated that in addition to carboxylic acids other components are involved in the host-seeking behaviour of female <em>An. gambiae</em> , studies were undertaken to identify new putative attractants (chapter 5). Rather than searching for minor differences in chemical odour profiles between different individuals, we focussed on components which are generally produced by every human host. Freshly collected pooled sweat samples obtained after physical exercise from a group of volunteers neither attracted female <em>An. gambiae</em> in a windtunnel bioassay, nor evoked a detectable EAG response. Incubation of the sweat samples, however, resulted in a behaviourally attractive source of volatiles which evoked reproducible EAG responses. Sweat obtained during physical exercise is most likely to originate from the eccrine and sebaceous glands. Several observations strongly indicated that during incubation attractants are produced by microbial activity. Although the fresh sweat did not elicit a behavioural or EAG response, it was possible that it may contain components which acted as synergists at the behavioural level together with components produced during incubation. Headspace analysis of the fresh and incubated sweat revealed that geranyl acetone (5%-6%) and 6-methyl-5-hepten-2-one (1.8%-1.9%) were relatively abundant in both the fresh and incubated headspace samples. Headspace samples of the incubated sweat comprised large amounts of indole (27.9%), 1-dodecanol (22.4%) and 3-methyl-1-butanol (10%). These components were absent or only present in minor amounts in the headspace samples of the fresh sweat. Indole, geranyl acetone and 6-methyl-5-hepten-2-one evoked an EAG response, while 1-dodecanol did not elicit any response. 3-Methyl-1-butanol was only tested at the single cell level (chapter 6).<p>In order to reveal olfactory receptor neurons responsive to the identified sweat-borne components, studies were conducted at the single cell level (chapter 6). For other mosquito species, such as <em>Aedes aegypti</em> , the grooved peg sensillum is considered to house receptor neurons sensitive to host odours. Indeed, incubated sweat elicited excitation of a receptor neuron innervating a subpopulation of the grooved peg sensilla in <em>An. gambiae</em> . The same receptor neuron was excited by ammonia, which was found to be present in large amounts in the incubated sweat. This strongly implies that ammonia is causing (most of) the attractiveness of the incubated sweat.<p>However, chemically identified components from the headspace of the fresh and incubated sweat (chapter 5) did not elicit responses of grooved peg receptor neurons. They evoked excitation of receptor neurons associated with the sensilla trichodea. Two different subpopulations were found, one was innervated by receptor neurons sensitive to indole, while the other subpopulation housed receptor neurons sensitive to geranyl acetone. 3-Methyl-1-butanol and 6-methyl-5-hepten-2-one elicited responses of receptor neurons associated with both subpopulations. Receptor neurons displayed lower sensitivity to 3-methyl-1-butanol and 6-methyl-5-hepten-2-one. Sensilla trichodea receptor neurons only occasionally responded to the source of the components, the incubated sweat.<p>It is suggested that not only the grooved peg receptor neurons encode host-odours but also the sensilla trichodea receptor neurons fulfill a function. The incubated sweat may evoke an increase in the spike frequency of only a few spikes per second and responses like these are very hard to detect. Another explanation might be that sensilla trichodea receptor neurons encode other behavioural activities, such as nectar feeding or location of oviposition sites. Identified sweat-borne components are very likely of microbial origin. Microbial products are very common in nature and therefore not restricted to human emanations (chapter 6).<p>Further studies on the behavioural level might elucidate the role of the identified sweat-borne components for the behaviour of <em>An. gambiae</em> . The function of the different olfactory receptor neurons in host-seeking <em>An. gambiae</em> is further discussed in chapter 7.<br/>
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