DI-UMONS : Dépôt institutionnel de l’université de Mons

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2010-10-07 - Colloque/Présentation - communication orale - Anglais - 1 page(s)

Caulier Guillaume , Flammang Patrick , Gerbaux Pascal , Rakotoarisoa Pricilla, Eeckhaut Igor , "When a repellent becomes an attractant: harmful saponins are kairomones that maintain the symbiosis between the Harlequin crab and their sea cucumber hosts" in European Conference on Echinoderm, Gottingen, Allemagne, 2010

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Abstract(s) :

(Anglais) Saponins are secondary metabolites produced by some plants and animals that use them as defensive repellents. They are well known in sea cucumbers in which they function as a chemical protection against predators. Sea cucumbers however house batches of obligate symbiotic organisms for which host selection is generally mediated by chemical signaling. This study is the first to highlight the precise chemical nature of the specific odor involved in the recognition of a sea cucumber by one of its symbionts. Host choice experiments performed using a Y-tube olfactometer demonstrate that saponins secreted by Bohadschia vitiensis are specifically recognized by and attracts one of its most common symbionts, the Arlequin Crab Lissocarcinus orbicularis. Conversely, saponins emitted by a non-host species of sea cucumber, Pearsonothuria graeffei, are not attractive to the crab. The chemical structure of the different saponins was resolved by mass spectrometry analyses. These analyses show that host saponins lack the sulfate group which is characteristic of most non-host saponins. In addition to their traditional defensive role (allomones), saponins therefore also function as kairomones, maintaining the symbiosis between the Arlequin crab and its sea cucumber host.