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The osmotic and ionic regulatory capacities of the kidney of the harbor seal, Phoca vitulina Tarasoff, Frederick John


The mechanisms of osmotic and ionic regulation in marine mammals are of interest because of the apparent lack of "fresh" water in their environment. Previous investigation on the harbor seal, (Phoca vitulina, L.), generally indicated that the seal can obtain all the water it requires from its food. However, some dispute still exists as to whether the seal may ingest sea water along with its food and conserve water by concentrating ions and excreting them with a net water gain. The effects of a 16-hour period with no fluids and also of intubation with varying amounts of distilled water and varying amounts and concentrations of sea water were determined. The concentrations of sodium, chloride and potassium ions as well as the osmotic pressures of plasma and urine were measured for the periods before and after intubation. The results of this study are discussed with respect to published data and proposed mechanisms of osmotic and ionic regulation by the kidney. The findings indicate, as suggested by others, that the seal does not gain any substantial amount of water from sea water ingestion.

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