Browsing by Subject "Pheromon"

Now showing 1 - 3 of 3

Lokalisation von Pheromon-Rezeptoren und -Bindeproteinen in antennalen Sensillen von Insekten
(2007) Gohl, Thomas; Breer, Heinz
The remarkable reactivity of moth to specific pheromones is based on the extreme selectivity and sensitivity of sensory cells in the male antennae. This feature is supposed to be based on cells equipped with specific receptors. Only the sequencing of the genomes of Bombyx mori and Heliothis virescens provided the possibility to identify candidate genes of olfactory receptors in moths. Upon detailed inspection of candidate receptors it turned out that within the generally very heterogeneous group of receptor-genes a subfamily exists containing members of both species showing striking sequence homology. A conservation of the primary structure of receptors for pheromones has been postulated. For a continuing characterization in these studies different approaches were used to verify that these receptors are indeed expressed in cells of pheromone-sensitive sensilla (sensilla trichodea). By means of ?whole mount? in situ hybridization experiments the RNA of the receptor types BmOR1 and BmOR3 could be visualized in directly neighboring cells reflecting the topology of trichoid sensilla. Also some of the Heliothis receptor types (HR13, HR14, HR16) could be assigned to sensilla trichodea. In addition to the specific receptors, the pheromone binding proteins (PBPs) are expected to play an important role in the detection of hydrophobic pheromone molecules. PBPs are produced by glia-like cells surrounding the sensory neurons. In double in situ hybridization experiments it could be shown that HR13-cells are indeed surrounded by cells expressing HvirPBP1 and HvirPBP2. Analysis comparing the topology of different receptor-types showed that cells expressing HR13 can be assigned to sensilla trichodea type A, whereas HR14 and HR16 are expressed in cells of sensilla trichodea type C. This characteristic expression pattern is considered as a further indication that these candidate-receptors are indeed pheromone-receptors. The assignment of individual receptor-types to distinct sensilla-types provides the basis for investigating the functional implications of receptor-types for the registration of main or minor components of complex pheromone-blends. Further it turned out that HR13 shows coexpression with SNMP1 (sensory neuron membrane protein 1) which is considered as a ?marker?-protein for antennal sensory neurons. This is however not the case for receptor types HR14 and HR16. In search of further SNMP-types screening-experiments were carried out which led to the identification of a novel SNMP-type (SNMP2) of Heliothis virescens. Subsequent studies concerning the expression of SNMP2 showed that the topologic distribution of SNMP2-cells is comparable to SNMP1-cells, but they show a different morphology. Further experiments revealed that SNMP2 is in fact expressed in PBP-producing cells. These findings imply that the proposed putative function of SNMPs has to be reconsidered. One major goal of this study was the attempt, to identify receptor-relevant cells by visualization of mRNA via in situ hybridization but to visualize the localization of the receptor-protein via immunohistochemical approaches. Although the generation of antibodies for olfactory receptors is very difficult, it was possible to raise antibodies specific for receptor type HR13. Using these antibodies in immunohistochemical approaches allowed to also visualize HR13-receptor-protein. By means of double-staining experiments using HR13-specific antisense RNA-probes and anti-HR13 antibodies mRNA and protein were visualized in the same specific cells. Using confocal laserscanning microscopy, it was possible to document that receptor-protein was indeed located in the sensory dendrites. Further, the receptor-protein was also visualized in the axonal processes of sensory cells and the receptor-specific staining revealed that within the antennal nerve HR13-axons appear to be organized in fascicles. These HR13-immunolabeled fascicles were visible until they reach the ?sorting zone? of the antennal lobe; in contrast to mouse olfactory bulb, no receptor specific staining was visible in the antennal lobe.
Prüfung von Citral als Zusatzstoff zu Pheromon zur Bekämpfung des Apfelwicklers Cydia pomonella L. (Lepidoptera, Tortricidae) und des Apfelbaumglasflüglers Synanthedon myopaeformis Borkh. (Lepidoptera, Sesiidae)
(2003) Hapke, Christine; Zebitz, Claus P. W.
In the years 1998 til 2000, a modification of the confusion technique was tested against two pest insects in apple, the Codling moth Cydia pomonella L. and the Apple clearwing Synanthedon myopaeformis Borkh. The respective pheromone was combined with the tentative monoterpene synergist Citral, and applied in the orchard at a density of 125 per hectare as recommended. Laboratory tests were conducted to characterize the effects of Citral mode on individuals of the pests. Field tests with Codling moth revealed no essential differences in the efficiency between the common confusion method with 500 pheromondispensers per hectare and the new technology with Citral (125 dispensers/ha) as expressed in numbers of male caught in pheromone traps or in percent fruit damage under low pest pressure. Both methods failed under high pest pressure. Weighing the dispensers weekly followed up the release of Citral and the pheromone. In semi-field tests in large cages (2 m  2 m  2 m) pest population density seemed to have no impact on control success. In small cages (30 cm height, 30 cm ) the copulation rate in the pheromone plot was significantly lesser than in the Citral-treated atmosphere and in the untreated control plot. Using a laboratory wind tunnel undiluted and 10-1 diluted Citral resulted in a significant decrease of the attractiveness of pheromone. After 24 hours this effect diminished. Half-life of released Citral was approximately two hours. After four hours about 100 µg/h 10-1 diluted Citral was still released into the tunnel. Electroantennogrammes of both, male and female antennae of C. pomonella showed a strong reaction to Citral. The reaction of the antennas to pheromone was strongly overlaid by Citral. In laboratory tests in a closed system, copulation of the moths could be prevented starting from a Citral concentration of 2000 mg/l. Male moths, previously exposed to Citral for 24 h, were not able to copulate with mature, unmated females. Citral-exposed females (24 h exposure time), however, were successfully mated by mature untretaed males. Any impact of Citral in concentrations up to 1,500 mg/l on oviposition could not be proven. Furthermore, first larvae of the Codling moth were not prevented to penetrate into an apple with up to 5,000 mg/l Citral. Field tests with the Apple clearwing proved significantly lesser pheromone trap catches in the Citral-treated plots than in the control plots on five alternatively six test orchards. The plots with 500 and 250 pheromone dispensers per hectare also exerted rates of confusion of up to 100 %. In a plot with 250 Citral dispensers per hectare, an effect of confusion could not be observed. Catches in lure pots showed no difference in the amount of mated or unmated females between plots. The amount of mated females in all plots was much higher than those of the unmated. The amount of fresh frass in treated and untreated plots was too small for proving a success of control. The quantitative preparation of the larvae in coincidentally selected trees on a plant showed a significant difference between the Citral-treated plot and the untreated control plot. However this difference is based only on a reduced number of larvae up to 7 mm body length. Tests with S. myopaeformis in a laboratory wind tunnel were not successful, because the attractiveness of the traps baited with pheromone were not very high. Investigating the environmental conditions for a successful copulation of S. myopaeformis the light intensity did not prove to play the major role. Temperature and wind velocity seem to possess a substantial meaning, dominating light. The copulation rate in small cages (30 cm height, 30 cm ) generally hardly reached 50 % and was very small thereby. In the laboratory moths of the apple clearwing could not be brought to copulation. Synergisation of pheromones with Citral seem to be not recommendable under practical conditions.
Reproduktionsbiologie und olfaktorisches Verhalten des Kleinen Beutenkäfers Aethina tumida MURRAY 1867 (Nitidulidae)
(2014) Mustafa, Sandra Gabriele; Steidle, Johannes
This dissertation aimed to investigate the olfactory behaviour and reproductive biology of the small hive beetle (Aethina tumida, Nitidulidae). Our investigations focused on the second part of the small hive beetle life cycle, after beetles emerged from the ground and invaded a honeybee (Apis mellifera) hive. Once in the hive, beetles show strong developed aggregation behaviour and start reproducing. We suspected the involvement of aggregation- and/or sexual pheromones in these social interactions. Our goal was to identify or at least to prove the existence of the latter. Three laboratory bioassays were developed on this purpose: aggregation-assay, filter-assay and choice-assay. Gender and age independent aggregation behaviour was revealed by the aggregation assay. The choice assay revealed a gender and age dependent preference for the opposite sex in both genders. The involvement of chemical substances in this system was proved by the filter-assay. Pieces of filter paper, which were left with certain beetle stages to leave marks on, proved to be attractive when offered to other beetles. A detailed description of the mating behaviour was supposed to reveal further information about chemical communication in the small hive beetle. Therefore an ethogram and flow diagram were compiled through video analysis of the mating behaviour. Several behaviours observed before, after and during copulation indicated chemical communication on tactile level; this included tapping, thrilling or rubbing of the cuticle surface of fellow mates. Electron microscopy pictures showed a high density of sensillae and pores on the areas involved in frequent behavioural interactions. The description of the mating behaviour revealed several indications for cryptic female choice mechanisms. One was the distinct aggressive behaviour of females in contrast to males. They pushed other beetles in high frequency and often interrupted matings this way. Comparison of matings in single pairs and aggregations showed that small hive beetles only copulate in aggregations and sexual behaviours reaches its peak at the ages from two to three weeks. It is further the only age in which more hetero- than homosexual matings occur. All these facts added up indicated female pheromone emission from the age of two weeks on. This feature might be seen as an extraordinary and unique adaption to their honey bee host. Single pairs would never be able to compete with the hygienic behaviour of the honeybees and all their offspring and eggs would be cleaned out immediately. It further helps in synchronizing reproduction of all beetles in an aggregation which in turn favours mass reproduction and surrendering the host. The central role of this mass reproduction strategy became further obvious when investigating the susceptibility of small nucleus hives to invasion of the small hive beetle. Nucleus hives were far more vulnerable to invasion of the small hive beetle than full sized colonies. After a four week study period under moderate invasion pressure, half of all 24 nucleus colonies showed signs of small hive beetle reproduction, namely they either collapsed or were infected with larvae in their final development stage. In contrast, none of the full-sized colonies showed any symptoms. Beekeepers in affected areas should consider this in their daily tasks and avoid using too-small nucleus colonies for queen rearing or colony propagation. The small hive beetle depends on the collapse of the colony to ensure its reproduction in contrast to many other parasites which try to keep their host alive as long as possible. In the first stage of the adult live cycle, after pupation and emergence from the ground, foraging and host-finding behaviour have first priority. Volatiles from fermenting honey might be a key trigger during this time. Infection with larvae incites fermentation of honey and pollen which produces the typical slimy combs in the end. Colonies in the stage between collapse and symptom-free infestation are supposed to be the most attractive. There are still food resources available but the honey bee host is already weak and vulnerable. In a preliminary trial under canvas we investigated the effect of various ferment products. They seemed to be attractive and could be considered as lure for traps in the field after further experiments. In conclusion one can say that it was possible to prove the existence of chemical- probably chemotactical communication via pheromones in the small hive beetle A. tumida. Olfactory orientation is present in all stages of the life cycle and aggregation and a mass reproduction strategy is closely connected to it on the reproductive and behavioural level. Thereby, this effective mass reproduction strategy may be the key to the success of this invasive species.