Seawater drinking restores water balance in dehydrated harp seals |
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Authors: | Ole-Jakob How Erling S Nordøy |
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Institution: | 1.Department of Arctic Biology and Institute of Medical Biology,University of Troms?, Breivika,Troms?,Norway;2.Department of Cardiothoracic and Vascular Surgery,University Hospital North Norway,Tromso,Norway |
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Abstract: | The purpose of this study was to answer the question of whether dehydrated harp seals (Phoca groenlandica) are able to obtain a net gain of water from the intake of seawater. Following 24 h of fasting, three subadult female harp
seals were dehydrated by intravenous administration of the osmotic diuretic, mannitol. After another 24 h of fasting, the
seals were given 1,000 ml seawater via a stomach tube. Urine and blood were collected for measurement of osmolality and osmolytes,
while total body water (TBW) was determined by injections of tritiated water. In all seals, the maximum urinary concentrations
of Na+ and Cl− were higher than in seawater, reaching 540 and 620 mM, respectively, compared to 444 and 535 mM in seawater. In another experiment,
the seals were given ad lib access to seawater for 48 h after mannitol-induced hyper-osmotic dehydration. In animals without
access to seawater, the mean blood osmolality increased from 331 to 363 mOsm kg−1 during dehydration. In contrast, the blood osmolality, hematocrit and TBW returned to normal when the seals were permitted
ad lib access to seawater after dehydration. In conclusion, this study shows that harp seals have the capacity to gain net
water from mariposa (voluntarily drinking seawater) and are able to restore water balance after profound dehydration by drinking
seawater. |
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Keywords: | Harp seals Mariposa Phoca groenlandica Seals Seawater drinking Water balance |
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