Distribution of Intracellular Sodium, Potassium and Chloride inArenicola MarinaEquilibrated to Diluted Sea Water

Abstract

In some earlier papers we have discussed the distribution of water and the total amounts of the major inorganic solutes in the cells ofArenicola marina(L.) equilibrated to full-strength and to diluted sea water (Freeman & Shuttleworth 1977b,c). We concluded that adaptation to dilute media by this osmoconforming worm was dependent entirely upon the regulation of cell volume. In dilute media substantial amounts of water do enter the cells but down to about 30% sea water this is only 55% of that which would have entered if the osmotic equilibrium was accomplished by entry of water alone. The influx of water is restrained by simultaneous loss of solute, an increasing amount of solute being lost or rendered osmotically inactive as the dilution increases. For lugworms in 35% sea water, for example, the volume of cell water has doubled compared with worms in 100% sea water, but the increase would have been far greater if the intracellular solutes had not declined by 30%.