Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
Ecol Evol
2022 Feb 10;122:e8597. doi: 10.1002/ece3.8597.
Show Gene links
Show Anatomy links
Physiological control of water exchange in anurans.
Lemenager LA
,
Tracy CR
,
Christian KA
,
Tracy CR
.
???displayArticle.abstract???
Research on water exchange in frogs has historically assumed that blood osmotic potential drives water exchange between a frog and its environment, but here we show that the "seat patch" (the primary site of water exchange in many anurans), or other sites of cutaneous water uptake, act as an anatomic "compartment" with a water potential controlled separately from water potential of the blood, and the water potential of that compartment can be the driver of water exchange between the animal and its environment. We studied six frog species (Xenopus laevis, Rana pipiens, R. catesbeiana, Bufo boreas, Pseudacris cadaverina, and P. regilla) differing in ecological relationships to environmental water. We inferred the water potentials of seat patches from water exchanges by frogs in sucrose solutions ranging in water potential from 0 to 1000-kPa. Terrestrial and arboreal species had seat patch water potentials that were more negative than the water potentials of more aquatic species, and their seat patch water potentials were similar to the water potential of their blood, but the water potentials of venters of the more aquatic species were different from (and less negative than) the water potentials of their blood. These findings indicate that there are physiological mechanisms among frog species that can be used to control water potential at the sites of cutaneous water uptake, and that some frogs may be able to adjust the hydric conductance of their skin when they are absorbing water from very dilute solutions. Largely unexplored mechanisms involving aquaporins are likely responsible for adjustments in hydric conductance, which in turn, allow control of water potential at sites of cutaneous water uptake among species differing in ecological habit and the observed disequilibrium between sites of cutaneous water uptake and blood water potential in more aquatic species.
FIGURE 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
FIGURE 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 of Pseudacris regilla was modified from a picture from Dr. Bobby Espinoza at CSUN
FIGURE 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 < .05 determined by analysis of variance and HSD posthoc tests
FIGURE 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) (Ѱsp–Ѱen). 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
Bentley,
Neurohypophyseal hormones in amphibia: a comparison of their actions and storage.
1969, Pubmed
Bentley,
Neurohypophyseal hormones in amphibia: a comparison of their actions and storage.
1969,
Pubmed
Bentley,
Zonal differences in permeability of the skin of some anuran Amphibia.
1972,
Pubmed
Burggren,
The interplay of cutaneous water loss, gas exchange and blood flow in the toad, Bufo woodhousei: adaptations in a terrestrially adapted amphibian.
2005,
Pubmed
Cree,
Effects of arginine vasotocin on water balance of three leiopelmatid frogs.
1988,
Pubmed
Heatwole,
Studies on anuran water balance. I. Dynamics of evaporative water loss by the coquí, Eleutherodactylus portoricensis.
1969,
Pubmed
Jørgensen,
200 years of amphibian water economy: from Robert Townson to the present.
1997,
Pubmed
Jørgensen,
Urea and amphibian water economy.
1997,
Pubmed
,
Xenbase
McClanahan,
Rate of water uptake through the integument of the desert toad, Bufo punctatus.
1969,
Pubmed
Ogushi,
Water adaptation strategy in anuran amphibians: molecular diversity of aquaporin.
2010,
Pubmed
,
Xenbase
Ogushi,
The water-absorption region of ventral skin of several semiterrestrial and aquatic anuran amphibians identified by aquaporins.
2010,
Pubmed
,
Xenbase
Preston,
Isolation of the cDNA for erythrocyte integral membrane protein of 28 kilodaltons: member of an ancient channel family.
1991,
Pubmed
Sinsch,
Reabsorption of water and electrolytes in the urinary bladder of intact frogs (genus Rana).
1991,
Pubmed
Spotila,
Determination of skin resistance and the role of the skin in controlling water loss in amphibians and reptiles.
1976,
Pubmed
Suzuki,
Amphibian aquaporins and adaptation to terrestrial environments: a review.
2007,
Pubmed
Suzuki,
Molecular machinery for vasotocin-dependent transepithelial water movement in amphibians: aquaporins and evolution.
2015,
Pubmed
,
Xenbase
Suzuki,
Molecular and cellular regulation of water homeostasis in anuran amphibians by aquaporins.
2009,
Pubmed
,
Xenbase
Tracy,
Field hydration state varies among tropical frog species with different habitat use.
2014,
Pubmed
Viborg,
Cutaneous blood flow and water absorption by dehydrated toads.
2005,
Pubmed
Viborg,
Cardiovascular and behavioural changes during water absorption in toads, Bufo alvarius and Bufo marinus.
2006,
Pubmed
Word,
Osmotically absorbed water preferentially enters the cutaneous capillaries of the pelvic patch in the toad Bufo marinus.
2005,
Pubmed
Young,
Comparative analysis of cutaneous evaporative water loss in frogs demonstrates correlation with ecological habits.
2005,
Pubmed
