ABSTRACT
The rosettes of crossed pedicellariae of Marthasterias glacialis show a definite excitability towards different stimulations. The reaction of pedicellariae to mechanical and chemical stimulation was studied, both qualitatively and quantitatively, in order to propose a functional interpretation. The rosettes were cut off and put into a petri dish containing filtered sea water. A platinum wire was used to perform mechanical stimulations of either the spine, the rosette, the outer or the inner side of the pedicellaria. The study of the rosettes' excitability was carried out through a separate analysis of each movement contributing to their overall activity. These results showed that pedicellariae are undoubtely very sensitive and typically react when mechanically and chemically stimulated. For instance, the repeated opening and closing movements of pedicellarial valves or the retracting responses of the pedicellariae were not observed when mechanically stimulated.
