Movement Responses of the Supratidal Gastropod Cenchritis muricatus to Seawater Under Experimentally Constrained Conditions

The beaded periwinkle (Cenchritis muricatus) inhabits supratidal rocky environments characterized by strong gradients in salinity, desiccation, and hydrodynamic disturbance. Preliminary observations suggested that individuals leave dry rocks more frequently when surrounded by seawater than freshwater, prompting an exploratory investigation of potential environmental cues underlying this behavior. Field-based pilot experiments in which periwinkles were placed on isolated dry rocks surrounded by either seawater or freshwater were conducted, while additional treatments varied rock height, surface char- acteristics, water depth, and salinity. Across experiments, periwinkles migrated away from rocks surrounded by seawater more frequently than those surrounded by freshwa- ter, although effect sizes varied and interactions with other factors were inconsistent. High variance and limited replication constrained statistical inference, and analyses are there- fore interpreted descriptively. Despite these limitations, results suggest that movement is not driven by immediate habitat benefits but may reflect sensitivity to salinity-associated contextual cues linked to large-scale disturbance risk. Escape behavior may be adaptive over long temporal scales associated with storm exposure, even if it appears maladaptive under experimentally constrained conditions. These findings highlight the importance of experimental scale in behavioral ecology and motivate future studies incorporating con- nected substrates, refuge gradients, and field-based validation to better resolve how su- pratidal gastropods respond to changing coastal conditions.