Righting

If a spider conch is overturned by a disturbance such as wave action or a predator, its soft body is in danger because its highly modified operculum cannot fully cover its aperture (Walls 1980). Therefore it is a high priority to right its shell to its original, safe position. One would think that this would be an extremely difficult task given the shear weight and morphological flatness of the shell. However, these remarkable gastropods have developed a mechanism to successfully right their shells with relative ease (Berg 1973). 

When a spider conch is overturned, its first response is to withdraw its body into its shell, so that only a small section of its foot is in sight. It will then slowly begin to emerge by first unfolding its foot and moving it posteriorly. The operculum is held perpendicular to the longitudinal axis of the shell aperture. The eyes protrude from the aperture and point upward and remain fairly still. The tentacles on the eyestalks may move slightly. Here it is in the "ready position". When safe to do so, it will extend its foot over either the shell's outer lip or the parietal area (depending on how the shell is lying on the substrate) and place its operculum under the edge of the shell. If enough purchase is obtained by the operculum in the substrate, the shell will be pulled over by contraction of the footstalk. If purchase is not obtained and the operculum slips, the spider conch will retract back to its ready position and start the process again.

It is less common for spider conchs to right their shells by extending over the outer lip (Berg 1973). This is because the hollow marginal digitations limit the areas where the foot can be positioned, and require more force to overcome (See Video 2).