Behavioral and Metabolic Responses to Emersion and Subsequent Reimmersion in the Freshwater Bivalve, Corbicula...

When exposed to air, the freshwater bivalve, Corbicula fluminea, displayed valve movement behaviors, such as mantle edge exposure, wider gaping "ventilatory" response, and an escape or "burrowing" response. The proportion of the emersion period spent in these behaviors, relative to valve closure, increased with decreasing temperature. Emersion at 35°C inhibited valve movement behaviors, whereas emersion in a nitrogen atmosphere stimulated ventilatory activity. High rates of aerial oxygen uptake (Mo2) were associated with initial valve opening and ventilatory behaviors, and lower Mo2 occurred during bouts of mantle edge exposure. Heart rate was affected by temperature, but not by mantle edge exposure. Heart rate increased during burrowing and ventilatory behaviors suggesting a hydraulic function for hemolymph. Emersed C. fluminea had short bursts of heat production followed by longer periods of lower heat flux when measured by direct calorimetry. The mean heat production rate was 1.11 mW (g dry tissue)-1, significantly higher than the mean value for clams exposed in a nitrogen atmosphere, 0.50 mW (g dry tissue)-1. On reimmersion, C. fluminea showed no significant "oxygen debt" until after three days aerial exposure. The bursts of activity, while emersed, may be the result of periodic renewal of oxygen stores followed by immediate oxygen use.