Identification of semiochemicals in bumblebees and their social parasites

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A primary aim of the project is the identification of semiochemicals with a function in the regulation of reproduction in bumblebee hosts and their social parasites. In a comparative approach, we will include a highly host specific parasite and a parasite that uses different host species. We will perform gas chromatography with antennographic detection (GC-EAD) and measure olfactory induced cardiac responses of odour samples of hosts and parasites to detect compounds that may play a major role as semiochemicals. Subsequently, GC-EAD active compounds will be identified by chemical analyses using the combination of gas chromatography and mass spectrometry (GC-MS) and synthesized. Finally, bioassays with callow host workers that are exposed to various synthetic mixtures of GC-EAD active compounds will be performed in order to identify dominance signals of the host queens or parasite females. We will compare the mechanisms, respectively semiochemicals that act in regulation of worker reproduction in both, hosts and parasites of the two investigated host-parasite systems. In a second part of the project we will identify chemical signals involved in host nest-recognition of the host specific and non host-specific Psithyurs species. We will perform Y-tube tests to compare the attractiveness of nest marking signals of various host- and non-host species to parasite females and electrophysiological and chemical analyses (GC-MS) to identify the active compounds. Finally we will test whether imprinting on host colonies plays a role in host nest searching parasite females. A comparative approach may open the chance to detect and trace basic mechanisms of chemical communication involved in bumblebee hosts and cuckoo bumblebees.