Mechanisms and specifictiy of sequestration in the genus Athalia

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Several species within the tenthredinid sawflies are well characterised by a specific phenomenon exhibited by the larvae, the ‚easy bleeding’. Slight mechanical damage of the larval integument is sufficient to provoke the release of haemolymph at that given spot, which acts deterrent on many antagonists. For a few sawfly species it has been shown that the deterrent principle is related to the host plant chemistry: larvae take up certain plant metabolites and sequester them in their haemolymph. The uptake mechanism is however unclear, as the sequestered metabolites of several host plants are glycosides that are usually rapidly hydrolysed by glycosidases after disruption of plant tissue. The main aim of the project is to characterise the specificity and mechanisms of the uptake and turn-over of sequestered plant metabolites in the sawfly genus Athalia. For A. rosae sequestration of glucosinolates from host plant species within the Brassicaceae will be studied in more detail. Comparisons with other Athalia species that feed on Brassicaceae and on Plantaginaceae will clarify common and derived features of sequestration mechanisms within the ‘easy bleeders’. The effectiveness of different sequestered metabolites as defence against predators will give insight in the adaptive values.