HEART-RATE IN RELATION TO DEHYDRATION IN THE SNAIL HELIX-ASPERSA MULLER (GASTROPODA, PULMONATA)

Common garden snails Helix aspersa Muller were subjected to 3 weeks of desiccation at 20 degrees C and 80% rh, during which the water content of the foot declined from an average of 85% in well hydrated individuals, to 80.7% of wet weight. In the same time, hemolymph osmolarity varied from 154 to 219 mOsmol/l, There is a highly significant correlation between these two variables, osmolarity being inversely related to foot water volume, suggesting that extra- and intracellular fluids are in osmotic equilibrium. No active snail had a blood osmolarity higher than 80 mOsmol/l and no quiescent snail bad one lower than 186 mOsmol/l. During progressive dehydration, the heart rate declined to about 63% of the initial rate.