Abstract
Insects have evolved a potpourri of mechanisms for manipulating the allelochemicals that fortify their preferred host plants. A concatenation of physiological and biochemical events frequently follows the ingestion of a toxic natural product and can eventuate in a variety of fates for the compound. A particular allelochemical may be absorbed, metabolized, and sequestered, whereas the fates of concomitant natural products may be very different. Some compounds may be directly excreted in the faeces and their concentration will thus mirror that in the plant. In other cases, selective absorption and sequestration combine to biomagnify minor constituents so that the concentration of these sequestered compounds in insect tissues differs drastically from their concentrations in the host plants.
The acridid Romalea guttata is utilized in this paper as a paradigmatic insect which eclectically processes ingested allelochemicals from a wide range of host plants. This generalist herbivore is eminently suitable as a model because it feeds on plants containing a veritable pharmacopoeia of toxic compounds. The proven sequestrative potential of its defensive glands further qualifies R. guttata as an excellent candidate for determining the fates of toxic phytochemicals. An analysis of this insect’s processing strategies for the compounds ingested after feeding on catnip (Nepeta cataria) reveals that for R. guttata variety is the spice of herbivorous life. The results of this investigation persuasively demonstrate that each insect species—and the phytochemical mixture that it ingests—must be regarded as a unique evolutionary case that constitutes a distinctively idiosyncratic phenomenon.
Résumé
Les insectes ont développé un potpourri de mécanismes pour manipuler les composés qui fortifient leurs plantes préférées. Un enchaînement d’évenements physiologiques et biochimiques découle fréquemment de l’ingestion d’un produit naturel et toxique et peut donner au composé des fortunes diverses. Un composé particulier peut àtre absorbé, transformé par métabolisme, et isolé, alors que les fortunes des produits naturels comcomitants peuvent àtre très différents. Certains composés peuvent àtre excrétés directement dans les fèces et leur concentration correspondra à celui de la plante. Dans les autres cas, l’absorption et l’isolement sélectifs se combinent pour augmenter biologiquement les constituants mineurs de sorte que la concentration des composés isolés dans les tissues de l’insecte différe radicalement de la concentration qui existe dans les plantes préférées. Dans cet article on examine la sauterelle Romalea guttata comme modèle qui utilise éclectiquement les composés ingérés d’un grand choix de plantes préférées.
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Blum, M.S., Whitman, D.W., Severson, R.F. et al. Herbivores and Toxic Plants: Evolution of a Menu of Options for Processing Allelochemicals. Int J Trop Insect Sci 8, 459–463 (1987). https://doi.org/10.1017/S1742758400022487
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DOI: https://doi.org/10.1017/S1742758400022487