Regulation of Seat-patch Water Potentials in Anurans
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Authors
Lemenager, Lee A.
Issue Date
2011
Type
Thesis
Language
Keywords
Anura , Blood osmositic potential , Regulation , Seat-patch , Water potential
Alternative Title
Abstract
Decades of research on water exchange in frogs have assumed that blood osmotic
potential drives water uptake. However, more recent reports have suggested an
intermediate control of the water potential partially separate from the osmotic potential of
blood. Some reports have speculated that seat-patch may act as a compartment of water
exchange between the blood and the environment. Thus, I have studied the water
potential of the seat-patch and blood to evaluated their roles in water uptake in frogs. The
water potentials of seat-patch and blood were measured for six anuran species, Xenopus
laevis, Lithobates pipiens, L. catesbeiana, Anaxyrus boreas, Pseudacris cadaverina and
P. hypochondriaca. Seat-patch water potentials were inferred from changes in body mass
between frogs and different aquatic environments whose water potentials were
manipulated by adjusting the osmolality of sucrose. Rates of water exchange by frogs
were plotted against the osmotic potentials of environmental solutions. The x-intercepts
of these graphs were taken to be the point at which water exchange is zero. The xintercept marks the point where the water potential of the frog seat-patch is equal to the
water potential of the environment. Seat-patch water potentials were compared across
species. The osmotic potential of blood was also measured for all species at several levels
of body hydration. These water potentials of blood were compared to the seat-patch water
potentials. More aquatic species had seat-patch water potentials that were less negative
than those of terrestrial species, and those seat-patch water potentials were different from
the water potentials of their blood. More terrestrial species had more negative seat-patch
water potentials that were similar to their blood water potentials. These findings indicate a physiological mechanism in anurans to control water potential of seat-patches that has
not previously been reported in the literature.
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In Copyright(All Rights Reserved)