Chemical Signals in Arthropods: New structural Motifs

Abstract

The semiochemisty of parasitc wasps was investigated. Female and male cuticle hydrocarbon blend of the jewel wasp Ampulex compressa is characterised by a sexual dimorphism. (6Z,9Z)-6,9-heptacosadiene is a key structure in the female blend. Related compounds are often pheromones in insects. 3,6-Dimethyl-2-isobutylpyrazine is part of the head space of unmated females of the digger wasp Liris niger. This compound evokes a strong response of the male antenna in electrophysiological experiments. The identification of novel spider lipids is another key topic in this thesis. The female and male lipid blend of Argyrodes elevatus contain wax esters consisting of multiple branched acids and alcohols. New methyl branched methoxyalkanes with the methoxy group at C-2 were identified in the dwarf spider Diplocephalus permixtus. Another chapter of this thesis describes the biosynthesis of even-numbered unsaturated hydrocarbons. 3Z,6Z,9Z-octadecatriene was used as model compound. First alpha-linolenoic acid is elongated to 11Z,14Z,17Z-20:COOH followed by alpha-oxidation under formation of 10Z,13Z,16Z-19:COOH. Final decarboxylation furnishes the alkatriene. Furthermore spider volatiles of male desert spider Agelenopsis aperta and female wasp spider Argiope bruennichi were analysed. Derivatives of gamma-butyrolactones, delta-valerolactones, (E)-2-configured aldehydes and unbranched 2-ketones were identified in Agelenopsis aperta males. These compounds must be considered as potential candidates eliciting catalepis in mature females to facilitate mating process for males. Body and web extracts of virgin Argiope bruennichi females contain trimethyl methylcitrate in a diastereomeric ratio of 25:1. Field tests proved that this blend is attractive for males. Additionally methods for the stereochemical analysis of diols were developed. (R)-dichloro-ethyl-methylbenzylsilane and C2-symmetric silylating reagents were synthesised and successfully applied for this purpose.