title: When a repellent becomes an attractant: harmful saponins are kairomones attracting the symbiotic Harlequin crab.
abstract: Marine organisms have developed a high diversity of chemical defences in order to avoid predators and parasites. In sea cucumbers, saponins function as repellents and many species produce these cytotoxic secondary metabolites. Nonetheless, they are colonized by numerous symbiotic organisms amongst which the Harlequin crab, Lissocarcinus orbicularis, is one of the most familiar in the Indo-Pacific Ocean. We here identify for the first time the nature of the molecules secreted by sea cucumbers and attracting the symbionts: saponins are the kairomones recognized by the crabs and insuring the symbiosis. The success of this symbiosis would be due to the ability that crabs showed during evolution to bypass the sea cucumber chemical defences, their repellents becoming powerful attractants. This study therefore highlights the complexity of chemical communication in the marine environment.
authors.affiliation: University of Mons - UMONS, Biosciences Institute, Biology of Marine Organisms and Biomimetics, 7000 Mons, Belgium.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Caulier
authors.forename: Patrick
authors.initials: P
authors.lastname: Flammang
authors.forename: Pascal
authors.initials: P
authors.lastname: Gerbaux
authors.forename: Igor
authors.initials: I
authors.lastname: Eeckhaut
mesh_terms: D000818:Animals; D003386:Brachyura / Q000502:physiology*; D002633:Chemotaxis / Q000502:physiology; D005260:Female; D008297:Male; D010675:Pheromones / Q000737:chemistry*; D012503:Saponins / Q000737:chemistry*; D012616:Sea Cucumbers / Q000502:physiology; D013559:Symbiosis
chemical_list: D010675:Pheromones; D012503:Saponins
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