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2014-12-13 - Colloque/Présentation - communication orale - Anglais - 1 page(s)

Caulier Guillaume , Flammang Patrick , Gerbaux Pascal , Eeckhaut Igor , "Comparison of the behavioral patterns of a symbiotic and a predatory crab chemically detecting diseased Holothuroids" in 21st Benelux Congress of Zoology, Liège, Belgium, 2014

  • Codes CREF : Ecologie chimique (DI312G), Biologie (DI3100), Ecologie (DI3123)
  • Unités de recherche UMONS : Synthèse et spectrométrie de masse organiques (S836), Biologie des Organismes Marins et Biomimétisme (S864)
  • Instituts UMONS : Institut des Biosciences (Biosciences)

Abstract(s) :

(Anglais) Skin Ulceration Disease (SUD) is a bacterial infection that induces serious lesions on the body wall of cultivated holothuroids (sea cucumbers). It is highly contagious and can cause the death of 95% of reared individuals. Healthy sea cucumbers Bohadschia vitiensis usually host the common symbiotic Harlequin crab Lissocarcinus orbicularis while Thalamita crenata is a predatory crab that usually feeds on holothuroids. Using host choices experiments in a Davenport olfactometer, we recently demonstrated that the symbiotic crabs are attracted by triterpenoid saponins that enable them to specifically recognize their hosts by means of chemical sensing. In this study, we observed that individuals of B. vitiensis presenting SUD were no longer attractive to L. orbicularis. Moreover, when given the choice between two sea cucumbers, Harlequin crabs were able to distinguish healthy individuals from diseased ones, with a significant preference for sea cucumbers that were not infected by skin ulceration disease. On the contrary, the predatory crabs Thalamita crenata, which were not attracted by holothuroid saponins, did recognize sick preys and preferred them to healthy ones. Using MALDI mass spectrometer, we measured similar concentrations of saponins in the extracts realized from the water conditioned by a healthy or SUD B. vitiensis. Both predatory and symbiotic crabs were not repelled by the bacteria cultured from the wounds of a diseased holothuroid. Genetic analyses revealed that these bacteria belong to the genus Vibrio. We finally highlighted that an artificially skin ulcerated individual had a repellent effect on symbionts but an attractive effect on predators. Both symbionts and predators are then able to discriminate if their hosts/preys are ill or not by sniffing surrounding water.