Exploring chemical stimuli guiding the pea crab Dissodactylus primitivus towards its echinoid host Meoma ventricosa.

International audienceSymbiotic associations require a specific communication between the host and the symbiont. In marine environments, host selection is essentially driven by chemical communication using specific metabolites also known as ecomones or semiochemicals. However, the chemical nature of these stimuli remains mostly unknown in aquatic environments. This paper explores the chemical identification of the signals allowing the pea crab Dissodactylus primitivus to recognize/find its host, the sea urchin Meoma ventricosa. We used a combination of behavioral tests aiming to monitor the chemotaxis reaction of crabs under water conditioned by different chemical cues. A classical Y-tube olfactometer was used to test pure industrial chemicals closely related to classes of molecules reported in echinoid tissues (i.e., quinonic and carotenoid pigments). A newly designed Petri-dish device was also developed to test biological fluids – mucus and perivisceral liquid- collected from the host M. ventricosa. Results show that 5,8-dihydroxy-1,4- naphtoquinone; 9–10 anthraquinones and beta-carotene allow a positive chemotaxis of the crab D. primitivus. On the other hand, the perivisceral fluid of M. ventricosa was repellent to the crabs, a behavior that may lead the crabs to select a healthy host. Based on other echinoderm-crustacean associations where the ecomones allowing host selection were identified, these results suggest that D. primitivus may benefit from several semiochemicals to locate and select its host M. ventricosa