VARIATION OF WATER CONTENT IN HELIX ASPERSA MULLER IN A NATURAL ENVIRONMENT

1. Daily and seasonal variations occur in the water content ofHelix aspersa Müller.
2. The water content is not constantthroughout 24 hours but fluctuatesby 2 to 10%. There is noapparent daily rhythm.
3. Humidity has an effect on the watercontent. Falls in relativehumidity to 60% or less, triggera decrease of the snails' hydration,over a range of temperatures,as well as a brief pause in activity.
4. Only external climaticconditions produce noticeable fluctuationsof water content,and they more particularly affect juvenileswhich undergo greaterevaporo-transpiration.
5. A seasonal rhythm in water contentexists in Helix aspersa,with maxima during spring and autumnand minima in June andJanuary.
6. The water content of juvenilesis always superior to that ofthe adults.
7. The water contentaffects the duration of the snail's activephase.

(Received 22 September 1988; accepted 5 February 1989)