Water and Electrolyte Balance of Goldfish Under Conditions of Anoxia, Cold and Inanition

¹ From the Department of Physiology and Pharmacology, University of Missouri, Columbia, Missouri

Small goldfish (Carassius auratus), average length 38 mm, were exposed to three conditions of stress, namely, acute anoxia, cold and inanition. Acute anoxia did not alter Na or K content of the body, but water increased 0.85%. Exposure to 4.0°C for 48 hours increased the water content 2.15%, but no change occurred in the absolute values of Na and K. Inanition for 2 and 7 weeks caused a progressive loss in dry weight without significantly altering the absolute amount of water. However, when total water was calculated on a dry weight basis, the increase was 3.81% for 2 weeks fasting and 6.74% for 7 weeks fasting. Sodium increased in absolute amount with fasting while K decreased. This inverse relationship showed a high correlation. For every milliequivalent of K lost, 1.2 mEq of Na was taken up. An important difference between the period of 2 and 7 weeks of fasting is discussed with respect to Na and K and their role in carbohydrate, fat and protein depletion.