Ken-ichi Yamamoto

Effect of Water Temperature on Discharge of Foreign Substances from the Mantle Cavity in the Pen shell Atrina (Servatrina) lischkeana

In the pen shell, Atrina (Servatrina) lischkeana (A. (S.) pectinata lischkeana), the effect of water temperature on the discharge of foreign substances from the mantle cavity was examined by observing sand perticles moving vertically and horizontally through the ciliated canal of the mantle. The average speed (mm/min) of sands moving was seasonally measured at the different temperature, 11 (January), 17 (April), 22 (June) and 27•Ž (August) which are approximate ambient temperature of the fields from which the pen shell were collected at the respective time points. The speed was also measured as the temperature was elevated 3•Ž every hour from each initial temperature up to a peak of 39•Ž . Both vertical and horizontal moving speeds increased and then decreased to zero mm/min after reaching the maximum with the rise in water temperature. However, the former speed was always smaller than the latter. The vertical movement peaked and ceased at a lower temperature than the horizontal moving. Based these findings, the pen shell will increase the discharge rate of foreign substances from the mantle cavity by increasing the activity of the cilium in the ciliated canal of the mantle, when water temperature rises over the at short term or depending on the season. However, the cessation and decrease in discharging foreign substances at an elevated temperature occurred without relation to the activity of the cilium.