The effect of DC-pulse electric stimulus on the swimming behavior of larvae of the freshwater mussel Limnoperna fortunei was investigated under flowing water conditions in a pipe. Freshwater mussel larvae were collected for microscopic observation after having been made to pass through an electric field by pumping lake water from a dam through a pipe electrode. Two types of pipe electrode configuration were tested: one with alternating+and-electrodes along the pipe and the other with several+electrodes between two-electrodes. In the case of the latter electrode configuration, 7kV voltage effectively immobilized the larvae and 80% of the larvae were stunned when given an electric stimulus (voltage x total pulse discharge) of approximately 270. Freshwater mussel larvae were effectively stunned with DC-pulse electric stimulus under flowing water conditions. Hence, installation of pipe electrodes upstream of target sites may prove an effective method of protection from mussel fouling by stunning passing larvae. In future studies, the settlement condition of the larvae after passing through the electric field will be investigated as part of our efforts to establish an antifouling method against the freshwater mussel using a DC-pulse electric system.

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Investigations of the factors that influence the cirral beating of barnacles are important because the survival and growth of barnacles after adhesion and metamorphosis depend on cirral beating. Only while beating their cirri are barnacles able to catch and ingest food, respire, and engage in reproduction and excretion. Although there have been some reports concerning barnacle cirral beating in the laboratory, there have been none with respect to this behavior in the field. The present research concerns the influences of water temperature, salinity, and diatom density on cirral beating in a species of sessile barnacle (Balanus amphitrite) in northern Osaka Bay, Japan. Cirral beating was observed throughout one year except when water temperature fell below 7°C, or salinity below 16.20‰. The frequency of cirral beating rose with rising water temperature but declined as the water cooled. Neither the highest water temperature (32.3°C) nor the highest salinity (32.16‰) observed during this study stopped cirral beating. Water temperature strongly affected the frequency of cirral beating in B. amphitrite, and to a lesser degree so did salinity, but diatom density did not.

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