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Journal of Experimental Biology 54,199-214 (1971)
Published by Company of Biologists 1971

Calcium Regulation in the Freshwater Mollusc, Limnaea Stagnalis (L.) (Gastropoda: Pulmonata) : I. The Effect of Internal and External Calcium Concentration

PETER GREENAWAY ¹

¹ Department of Zoology, University of Newcastle upon Tyne

1. Calcium regulation in normal and calcium-depleted snails has been investigated.

2. L. stagnalis has an uptake mechanism with a high affinity for calcium ions and shows a positive calcium balance in media containing more than 0.062 mM Ca/l.

3. Influx and net uptake of calcium are related to external calcium concentration in a non-linear manner. The uptake mechanism is half-saturated and near-saturated in external media containing 0.3 and 1.0-1.5 mM Ca/l respectively.

4. Calcium uptake from external concentrations of less than 0.5 mM Ca/l is against a small electrochemical gradient whereas from external concentrations greater than 0.5 mM Ca/l there is no adverse gradient.

5. Calcium depletion does not significantly alter the normal influx or net uptake rate of calcium from 1.0 mM Ca/l.

6. The calcium concentration in the blood remains constant during net uptake from, and net loss to, the medium.

7. A comparison is made between the mechanisms of sodium regulation and calcium regulation in L. stagnalis.