Cations in molluscan tissues at sharply different hemolymph osmolality

Experiments on different bivalve and gastropod species living in fresh, brackish, and sea water of different salinity demonstrated a direct correlation between the osmolality of the hemolymph and interstitial fluid and the concentration of sodium ions in it. A direct correlation between the osmolality of the interstitial fluid and the content of potassium and magnesium ions in the tissues (adductor and foot) was revealed. The significance of physicochemical indices of the environment and formation of eukaryotic cells at the initial stages of animal evolution are discussed.