Meeting Abstract
Each rhopalium of scyphomedusae contains a terminal statolith, suggesting that this part of the rhopalium, or the full rhopalium, functions in sensing body position relative to gravity. The righting response of pelagic scyphomedusae has been documented, but the location of sensory cells involved in this response has not been shown unequivocally. One proposal is the statolith acts as a weight, and changes in the sag of the rhopalium is detected as the animal tilts. Our video data indicate, however, that the rhopalia are stiff structures that do how significant sag. Another suggestion is that patches of putative sensory cells, called touch pads, are involved in tilt-related detection. Our comparative examination of two scyphomedusae, one pelagic and one primarily benthic, shows the presence of putative sensory cells associated with both the rhopalium and the surrounding tissues, with differences in the distribution of these sensory cells in the two species. This suggests detection of body tilt involves both the rhopalia and the surrounding tissues.
