San Diego, CA -- Most terrestrial amphibians acquire water by absorption across their skin rather than by oral drinking. During periods of rehydration, frogs and toads adopt a posture termed "water absorption response" (WR), thrusting their hindlimbs backwards and pressing the belly surface on to any surface containing water. In many frog and toad species, such as the Bufo breed, a specific area of the belly skin (the seat patch), is used for absorbing water. Even though the seat patch skin only constitutes about ten percent of the total skin area, it is responsible for over 70 percent of the total water uptake by dehydrated toads.

The seat patch skin is equipped with an elaborate capillary network. Interrupting capillary perfusion of isolated skin and in living animals results in a washout of salts from the interstitial fluid of the skin, thereby decreasing the osmotic gradient and the osmotic water flow across the skin. Circulation in the skin of this patch seems vital to this process, yet very few studies have investigated rates of blood flow in the seat patch skin while toads were exhibiting water absorption behavior.

The Study

A new study has been undertaken to assess blood flow in this patch and investigate how blood flow responds to water exposure. The study was divided into the following three parts:

(1) measuring red cell velocity and water uptake across the seat patch concurrently and related to the expression of water absorption postures by hydrated and dehydrated toads, Bufo woodhousei. This tested the hypotheses that: (a) the increase in red cell velocity, like that in the European common toad Bufo bufo, is greater in dehydrated animals after water exposure, (b) the expression of water absorption behavior is coupled to the increase in red cell velocity and (c) water uptake is correlated with the level of red cell velocity;

(2) using a procedure similar to the above, the researchers tested the h
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Contact: Donna Krupa
djkrupa1@aol.com
703-967-2751
American Physiological Society
26-Aug-2002

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