Search

Between 1976-1978, we studied the ecology of the Sphincterochila prophetarum, the most common snail, on stony slopes in Northern Negev. Energy and water flow determinations were made at the individual and population levels on a field observation basis and metabolic data were derived from laboratory simulations.The snails are active during 5-7% of the time during the year, while the remaining 95% of the time, the snails are in aestivation under stones. The energy and water inputs during the short feeding periods are very fast. Only 8% of the total energy in the eaten food are assimilated. Eighty-nine percent of the total assimilated energy are utilized in respiration during the various periods of activity and dormancy.The water loss during the feeding and activity period is about 37% of the total annual input. The snails lose twice as much the amount of water during the winter dormancy periods than in the summer dormancy period.

Natural, mixed algal populations grew well in artificial culture media of different pH levels between 5 and 12. Algal growth caused marked changes in the pH of the culture media, raising the low pH values and lowering the high ones. Within 3-4 weeks all cultures reached the pH range of 8.5-11.0, while sterile controls retained a much wider range of 4.0-10.0. Final pH values were temperature dependent, as also was the rate of the pH change.