Skalstad I, Nordøy E S
Department of Arctic Biology, Institute of Medical Biology, University of Tromsø, Breivika, Norway.
J Comp Physiol B. 2000 Sep;170(5-6):395-401. doi: 10.1007/s003600000116.
This study was undertaken to measure whether young harp seals (Phoca groenlandica) and hooded seals (Cystophora cristata) drink seawater and, if so, to investigate how the excess salt load is handled. Blood and urine samples were collected from hooded seal pups (n = 3) and harp seal pups (n = 3) after 2 weeks of freshwater exposure, at intervals during 3 weeks of seawater exposure and, finally, after 2 weeks of re-exposure to fresh water. Total water turnover, as measured by injection of tritiated water, was 2200 ml x day(-1) and 3300 ml x day(-1) in hooded seals and harp seals, respectively. The extent of mariposia was taken as the difference between total water turnover and influx of water through food (free and metabolic water) and respiratory water exchange. Seawater drinking amounted to 14% and 27% of total water turnover (rH2O) for the hooded seals and harp seals, respectively. Further evidence of mariposia was obtained from an increase in the excretion rate of the urine osmolytes Na+, Cl- and Mg2+, during the period of seawater exposure. It is concluded that water influx due to seawater drinking can not be excluded as a source of error when estimating food consumption of free-ranging harp seals and hooded seals, by use of labeled water techniques.
本研究旨在测定幼年格陵兰海豹（Phoca groenlandica）和冠海豹（Cystophora cristata）是否饮用海水，若饮用，则研究它们如何处理过量的盐分负荷。在淡水暴露2周后、海水暴露3周期间每隔一段时间以及最后再次暴露于淡水2周后，从3只冠海豹幼崽和3只格陵兰海豹幼崽身上采集血液和尿液样本。通过注射氚水测量，冠海豹和格陵兰海豹的总水周转率分别为2200毫升×天⁻¹和3300毫升×天⁻¹。舐饮海水的程度以总水周转率与通过食物摄入的水（自由水和代谢水）以及呼吸水交换的水流入量之间的差值来衡量。冠海豹和格陵兰海豹舐饮海水分别占总水周转率（rH₂O）的14%和27%。在海水暴露期间，尿液渗透压物质Na⁺、Cl⁻和Mg²⁺的排泄率增加，这进一步证明了舐饮海水的存在。得出的结论是，在使用标记水技术估算野生格陵兰海豹和冠海豹的食物消耗量时，不能排除饮用海水导致的水流入作为误差来源。
