In order to investigate the behavior of the pen shell Atrina lischkeana under aerobic and hypoxic conditions, the valve movement of these pen shells was recorded using the strain gauge method. The experiments were carried out from December 17 to 26, 2002. Two patterns of valve movement were recorded under aerobic conditions: multi-close-open action and single close-open action. The multi-close-open action is characterized by a series of close-open actions, which are repeated at interval of less than 30 seconds. This action was observed during the burrowing behavior of the pen shell. The single close-open action is characterized by a close-open action that occurs at intervals greater than 4 minutes; this action occurs during vomiting behavior. The single close-open action occurred more frequently under hypoxic conditions than under aerobic conditions, and a high frequency of this action was associated with creep-out behavior. These results indicate that the characteristics of valve movement may be a good indicator of pen shell physiology under aerobic and hypoxic conditions.
