|All Authors / Contributors:
Stanley S Hillman
In an attempt to understand the physiological mechanisms which have led to differential dehydration tolerance in anuran amphibians, measurements of heart ventricle weight, plasma volume, hematocrit, comparative tissue water contents and sodium concentrations at critical activity point (CAP) following dehydration and salt load were made in six species of anuran amphibians. Dehydration tolerance (% of initial body weight lost at CAP, x̄ ± 2 SE) of the six species were: Xenopus laevis, 33.8 ± 1.0; Rana muscosa, 37.0 ± 1.2; Rana pipiens, 37.3 ± 0.9; Bufo boreas, 41.4 ± 2.0; Bufo cognatus, 42.9 ± 1.0; and Scaphiopus couchii, 44.9 ± 1.4 There were positive correlations between relative ventricle weight and dehydration tolerance, ventricle weight and hematocrit at CAP, plasma volume and dehydration tolerance and sodium concentration at salt load CAP and sodium concentration at dehydrational CAP. There were no or weak correlations between dehydration tolerance and initial hematocrit, hematocrit at CAP, comparative water homeostasis in ventricle and skeletal muscle, and initial plasma sodium concentration. The most consistent physiological predictor of differential dehydration tolerance in the species studied appears to be tolerance to increasing sodium concentrations.