Figure Legends
Fig. 1. The rate of water exchange, corrected for cutaneous evaporative water loss, for six anuran species (mean ± SD) exposed to different environmental water potentials (sucrose solutions). The x-intercept of the slope is taken to be the point at which no net water exchange occurs and is therefore where the water potential of the seat patch (or ventral site of water uptake) is equal to the environmental water potential. Data points are mean water uptake rates for all frogs at a given environmental water potential. The linear equations for the rate of water exchange between a frog and its environment were calculated using the filled circles, whereas the open circles represent points at higher water potentials at which water uptake rates were similar regardless of water potential. Mean and standard deviations of standard body masses are given under the names of species. Note that the whole-body water uptake varies with body size, so the scales of Y-axes differ among species.
Fig. 2. The water potential of the seat patches (or ventral sites of water uptake) (mean ± SD) of six anuran species dehydrated to 90% standard body mass. Sample sizes are given in parentheses. Species have been arranged in order of increasing terrestriality from left to right. Similar letters in the histogram bars indicate no significant difference between bars determined by analysis of variance with HSD post hoc tests at the 0.05 level. Pictures of frogs mostly came from thumbnails of photos available on AmphibiaWeb: Cal Photos. 2021. Regents of the University of California, Berkeley. Accessed June 7, 2021. Available online at: https://calphotos.berkeley.edu/. The photo ofPseudacris regilla was modified from a picture from Dr. Bobby Espinoza at CSUN.
Fig. 3. Comparisons between the water potentials of the seat patches (or ventral sites of water uptake) and the water potentials of their blood in six anuran species dehydrated to 90% of their fully hydrated mass. Data are means ± SD; * denotes statistical significance at P< 0.05 determined by analysis of variance and HSD posthoc tests.
Fig. 4. Model of water exchanges between the environment, seat patch (or ventral site of water uptake), and blood of a frog. The rate of water uptake from the environment through the skin surface (as described by Equation A ) depends on the surface area of the seat patch (or ventral site of water uptake) that is exposed to water (A v), the hydric conductance of the skin (K sp), and the concentration gradient between the surrounding environment and the seat patch (or ventral site of water uptake) (Ψspen). Similarly, water movement from the seat patch (or ventral site of water uptake) into the blood (as described by Equation B ) depends on surface area, hydric conductance, and the concentration gradient between the seat patch and blood within the cutaneous blood vessels.
Figure 1