Temperature and Relative Humidity Effects on Aerial Exposure Tolerance in the Freshwater BivalveCorbicula fluminea

The exposure tolerance, aerial respiratory behaviors, and the rates of water loss of the Asian freshwater clam, Corbicula fluminea, were assessed under three temperature conditions (15°, 25° and 35°C) and five relative humidity (RH) treatments (5%, 33%, 53%, 75% and 95%). C. fluminea displayed low tolerance to aerial exposure (range of median tolerance times: 23.8-24.9 h at 35°C, 71.4-78.2 h at 25°C, and 248.5-341.6 at 15°C). Relative humidity had no effect on median tolerance time except at 15°C. Body size was reciprocally related to water loss rate at all temperatures, and on longevity at 25° and 35°C. Cumulative rates of water loss at 95% and 75% RH were lower than the other humidities at 15°C, but no differences were found at 25° or 35°C. Mantle edge exposure behavior was inhibited by low humidity and high temperature. Exposing mantle tissues did not increase rate of water loss except at humidities below which the behavior was very rare. The occurrence or extent of the behavior did not affect individual clam longevity. The results suggest that C. fluminea can detect rates of desiccation and make behavioral adjustments.