Do Frogs Drink?

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Abstract
Drinking in response to dehydration and exposure to saline solutions was measured in adult Rana pipiens, Bufo marinas and Xenopus laevis, and tadpoles of Rana catesbeiana. These animals normally occupy quite different types of environments where the possible advantages of drinking may differ. Small amounts of the external media were swallowed by all the animals and the quantity usually increased when they were placed in hyperosmotic NaCl solution. However, no relationship between the oral intake of water and the particular conditions, such as the degree of dehydration, was observed. Usually 80–90% of the total water uptake occurred by absorption across the skin. Thus although ‘secondary’ type drinking takes place, ‘primary’ drinking did not appear to occur. These results directly confirm the general popular impression that amphibians, in contrast to other tetrapods and marine teleosts, do not drink in order to rehydrate.