Ionic Regulation in the Queen Conch, Strombus Gigas (Gastropoda, Prosobranchia)*

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Abstract
1. The concentrations of sodium, potassium, calcium, magnesium, bicarbonate, chloride and sulphate in the haemolymph of Strombus have been measured. Greatest differences between concentrations in haemolymph and sea water were found for bicarbonate and sulphate. 2. Haemolymph has been compared with haemolymph dialysed against sea water, and the comparison suggests that sodium, calcium, magnesium and chloride are in passive equilibrium; potassium is actively absorbed, and sulphate is actively eliminated. 3. Nernst potentials have been calculated for the measured concentration ratios of ions in haemolymph and sea water, and have been compared with the potential difference measured between haemolymph and sea water in vivo. These observations show that sodium and magnesium are in passive equilibrium; chloride is taken up actively (significant at the 5% level of probability) and potassium may be taken up actively (significant at the 10% level); calcium and sulphate are actively eliminated (significant at the 5% level). The differences between these conclusions and those derived from dialysis experiments are discussed. 4. Analyses have been made of the composition of pericardial and kidney fluid, and the rate of loss of urine has been measured. It is concluded that pericardial fluid is produced by ultrafiltration from the haemolymph; the mean rate of production of urine is low, at 11.5% of the blood volume per day (3 ml./kg./hr.), but small differences of concentration between haemolymph and sea water indicate that calcium and potassium must be lost at a relatively faster rate than other ions. 5. Analyses have been made of the composition of stomach fluid. This contains almost no sulphate or bicarbonate, but the concentrations of other ions are similar to those of haemolymph, except for calcium, which is probably derived from calcareous sand grains. The basic mechanism of formation of stomach fluid has not been explained. The rate of loss of stomach fluid to the exterior is very slow (0.10-0.16 ml./ kg./hr.), but this fluid is rinsed out of the rectum by sea water drawn in from the outside. 6. An analysis of one sample of mucus from the mantle cavity suggests that mucus glands may be responsible for the low concentration of sulphate in the haemolymph.

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