Thermal tolerance and evaporative water loss of the mangrove prosobranch Tympanotonus fuscatus var. radula L. (Cerithiacea: Potamididae).

Rate of weight loss and mortality, of the Nigerian periwinkle, Tympanotonus fuscatus var. radula L. were investigated during prolonged exposure to air for one month. Short term thermal tolerance in the laboratory was carried out by heating the water in which the animals are placed at the rate of 1 degree C every 10 min. The group exposed to air continued to lose weight; when the experiment was terminated after 4 weeks, 20% of body weight was lost and 5 out of 40 periwinkles died, while the control experimental snails lost 11% of body weight, due to starvation. The species has an upper lethal temperature of 46-48.5 degrees C, much higher than the temperature of its habitat. Survival of T. fuscatus var. radula out of water and adaptation to high temperature suggests the presence of highly adaptive mechanisms of water balance and metabolism.