Water Balance and Arginine Vasotocin in the Cocooning Frog Cyclorana platycephala (Hylidae)
It is well established that forming a cocoon, for frog species capable of doing so, markedly reduces evaporative water loss; however, the capacity of cocooned frogs to maintain hydration during extended estivation is not well understood. The combined effects of long-term estivation and water loss we...
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Published in | Physiological and biochemical zoology Vol. 81; no. 1; pp. 43 - 53 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
United States
The University of Chicago Press
01.01.2008
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Subjects | |
Online Access | Get full text |
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Summary: | It is well established that forming a cocoon, for frog species capable of doing
so, markedly reduces evaporative water loss; however, the capacity of cocooned
frogs to maintain hydration during extended estivation is not well understood.
The combined effects of long-term estivation and water loss were examined
in the cocoon-forming species Cyclorana platycephala by
assessing the hydration state of the frogs throughout a 15-mo estivation
period. Frogs lost mass throughout the 15-mo period to a maximum of
36% ± 6.5%
of their initial standard mass. Plasma osmolality reached maximal levels by the
ninth month of estivation at 487 mOsm kg−1 and then remained
stable to the fifteenth month of estivation. Urine osmolality continued to
increase to the fifteenth month of estivation, at which point plasma and urine
concentrations were isosmotic. The use of bladder water to counter losses from
circulation was indicated by the relatively slow rate of increase in plasma
osmolality with mass loss and the progressive increase in urine osmolality. For
estivating frogs, evidence was found for a possible threshold relationship
between plasma osmolality and plasma arginine vasotocin (AVT) concentration.
After estivation, plasma AVT concentrations decreased markedly after
15-mo estivators were placed in water for 2 h, suggesting that high
levels of AVT may not be integral to rapid rehydration in this species. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1522-2152 1537-5293 |
DOI: | 10.1086/523856 |