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Leaf beetles fascinate us because of their amazing variety of shapes and rich coloring. Their larvae, however, are dangerous plant pests. Larvae of the leaf beetle Chrysomela lapponica attack two different tree species: willow and birch. To fend off predator attacks, the beetle larvae produce toxic butyric acid esters or salicylaldehyde, whose precursors they ingest with their leafy food. Scientists of the Max Planck Institute for Chemical Ecology in Jena, Germany, now found that a fundamental change in the genome has emerged in beetles that have specialized on birch: The activity of the salicylaldehyde producing enzyme salicyl alcohol oxidase (SAO) is missing in these populations, whereas it is present in willow feeders. For birch beetles the loss of this enzyme and hereby the loss of salicylaldehyde is advantageous: the enzyme is not needed anymore because its substrate salicyl alcohol is only present in willow leaves, but not in birch. Birch beetles can therefore save resources instead of costly producing the enzyme. First and foremost, however, the loss of salicylaldehyde also means that birch feeding populations do not betray themselves to their own enemies anymore, who can trace them because of the odorous substance. (PNAS Early Edition, DOI 10.1073/pnas.1013846108)
Defensive glands and toxic cocktails
Beetle larvae are part of a food chain. They are attacked by predatory insects and parasites, such as hover flies and bugs, as well as infested by bacteria and fungi. To protect themselves some leaf beetle larvae have developed interesting defense mechanisms, which function externally and metabolically: In case of danger, they emit substances from their defensive glands in form of vesicles (see picture; a short video is also available on http://
|Contact: Wilhelm Boland|
Max Planck Institute for Chemical Ecology