To see or to smell: the role of vision in host-recognition by an ectoparasitic crab
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Crustaceans are associated with a wide diversity of hosts, using both chemical and visual cues to recognize them. The pea crab Dissodactylus primitivus is an ectoparasite of two species of irregular echinoids living in the Caribbean Sea. Previous studies showed that the crab chemically discriminates its hosts from non-host species. The possibility that the parasite also visually localizes its host was investigated here through behavioral and morphological approaches. The responses of the parasite to visual cues were investigated in aquaria and show a limited visual ability, leading to sheltering rather than to host localization. This suggests that visual cues are not required to maintain the specificity of the parasitism. Microscopical investigations corroborate this conclusion by revealing a pair of small compound eyes mainly localized under the cephalothorax. The ommatidia (facets) were only found on the covered surface (below the cuticle). Interestingly, a lot of setae were observed around or even directly on the eye and might participate in the overall chemical detection.
KeywordsParasitism Visual recognition Pinnotheridae Echinoids Behavior Eye
We are grateful to the staff of the Discovery Bay Marine Laboratory for providing accommodation and laboratory facilities and to the National Environment & Planning Agency of Jamaica (NEPA) for the research permit. Research was supported by an FNRS-FRFC (Fonds de la Recherche Scientifique) research grant (Symbioses – T.0056.13) and by two Agathon De Potter travel grants (“Académie royale de Belgique”) to Quentin Jossart and Guillaume Caulier. We thank Emma Palacios Theil, Jérôme Delroisse and Magnus Lindström for their helpful advices.
Conceived and designed the experiments: QJ, LT, CDR, GC. Performed the experiments: QJ, LT, DM, GC. Analyzed the data: QJ, LT, CDR, GC. Contributed reagents/materials/analysis tools: CDR, IE. Wrote the paper: QJ, LT, CDR, IE, DM, GC.
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