Finicky Feeders

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Science  24 Sep 2004:
Vol. 305, Issue 5692, pp. 1875
DOI: 10.1126/science.305.5692.1875c

Dietary preferences within the animal world are varied, from our own omnivorousness to rather more specialized tastes, for example, that of the panda for bamboo. These are generally thought to be the outcome of many generations of evolution, particularly in cases where the eaten throw up defenses that the eaters must overcome, such as when insects feed on noxious plants. Kuhn et al. have examined how leaf-munching beetles (Chrysomela populi and Phratora vitellinae) might have not only refined their abilities to deal with the plant-derived chemical ordnance but also succeeded in adapting their internal biochemistry so as to expand their menu.

The ancestral coping mechanism enables chrysomeline larvae to synthesize the iridoid terpene chrysomelidial and to release this when attacked. Acquisition of an uptake pathway for the O-glucoside of 8-hydroxygeraniol (an iridoid precursor in the plant) provided a quicker route as well as allowing the larvae to benefit from a pinch of sugar. Further transporter modifications have led to beetles in this lineage being able to absorb the O-glucoside of salicin (a defense used in another family of plants) and convert it, following existing enzymatic routes, to salicylaldehyde, thus turning themselves into an unpalatable mouthful. — GJC

Proc. Natl. Acad. Sci. U.S.A. 101, 13808 (2004).

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