Clifford A. Hui
1981
<p><span>Two captive female </span><span class="single_highlight_class">common</span><span> </span><span class="single_highlight_class">dolphins</span><span> (59 kg and 55 kg) were given intravenous injections of tritiated </span><span class="single_highlight_class">water</span><span> (HTO) and sodium-22 (Na-22) after the first day of a 5-day fast. Blood samples were collected each of the next 4 days. Total body </span><span class="single_highlight_class">water</span><span> was 37% of total body weight, and the mean rate of </span><span class="single_highlight_class">water</span><span> turnover was 77 ml∙kg⁻¹day⁻¹. This low value for total body </span><span class="single_highlight_class">water</span><span> of a mammal is due to the high blubber content of the body. Exchangeable sodium levels were 37 and 40 meq∙kg⁻¹, with turnover rate of 6 meq∙kg⁻¹ day⁻¹. Skin was shown to be impermeable to sodium, so the only sodium source for these animals was </span><span class="single_highlight_class">seawater</span><span>. </span><span class="single_highlight_class">Seawater</span><span> drunk at a rate of 12 and 13 ml∙ kg⁻¹day⁻¹ accounted for the observed sodium turnover and about 1/6 of the total </span><span class="single_highlight_class">water</span><span> turnover. Estimated </span><span class="single_highlight_class">water</span><span> turnover from food and </span><span class="single_highlight_class">seawater</span><span> </span><span class="single_highlight_class">consumption</span><span> is the same as total </span><span class="single_highlight_class">water</span><span> turnover predicted for terrestrial mammals of the same weight. However, the low body </span><span class="single_highlight_class">water</span><span> content of these </span><span class="single_highlight_class">dolphins</span><span> indicates that they have a high fractional rate of </span><span class="single_highlight_class">water</span><span> turnover. Most of the body </span><span class="single_highlight_class">water</span><span> turnover is due to the permeability of the skin. The rapid fractional </span><span class="single_highlight_class">water</span><span> turnover, </span><span class="single_highlight_class">seawater</span><span> </span><span class="single_highlight_class">consumption</span><span>, and dilute urine indicate that conservation is not a major aspect of the fasting </span><span class="single_highlight_class">dolphin's</span><span> </span><span class="single_highlight_class">water</span><span> budget. Feeding </span><span class="single_highlight_class">dolphins</span><span>, however, may benefit from the urinary osmotic space that </span><span class="single_highlight_class">seawater</span><span> provides for the urea produced by protein catabolism.</span></p>
application/pdf
10.1086/physzool.54.4.30155836
en
The University of Chicago Press
Seawater consumption and water flux in the common dolphin Delphinus delphis
article