| Physiological ecology of aquatic overwintering in ranid frogs. | |
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MedLine Citation:
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PMID: 18429765 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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In cold-temperate climates, overwintering aquatic ranid frogs must survive prolonged periods of low temperature, often accompanied by low levels of dissolved oxygen. They must do so with the energy stores acquired prior to the onset of winter. Overwintering mortality is a significant factor in their life history, occasionally reaching 100% due to freezing and/or anoxia. Many species of northern ranid frogs overwinter in the tadpole stage, which increases survival during hypoxic episodes relative to adults, as well as allowing for larger sizes at metamorphosis. At temperatures below 5 degrees C, submerged ranid frogs are capable of acquiring adequate oxygen via cutaneous gas exchange over a wide range of ambient oxygen partial pressures (PO(2)), and possess numerous physiological and behavioural mechanisms that allow them to maintain normal rates of oxygen uptake across the skin at a relatively low PO(2). At levels of oxygen near and below the critical PO(2) that allows for aerobic metabolism, frogs must adopt biochemical mechanisms that act to minimise oxygen utilisation and assist in maintaining an aerobic state to survive overwintering. These mechanisms include alterations in mitochondrial metabolism and affinity, changes in membrane permeability, alterations in water balance, and reduction in cellular electrochemical gradients, all of which lead to an overall reduction in whole-animal metabolism. Winter energetic requirements are fueled by the energy stores in liver, muscle, and fat depots, which are likely to be sufficient when the water is cold and well oxygenated. However, under hypoxic conditions fat stores cannot be utilised efficiently and glycogen stores are used up rapidly due to recruitment of anaerobiosis. Since ranid frogs have minimal tolerance to anoxia, it is untenable to suggest that they spend a significant portion of the winter buried in anoxic mud, but instead utilise a suite of behavioural and physiological mechanisms geared to optimal survival in cold, hypoxic conditions. |
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Authors:
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Glenn J Tattersall; Gordon R Ultsch |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.; Review |
Journal Detail:
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Title: Biological reviews of the Cambridge Philosophical Society Volume: 83 ISSN: 1464-7931 ISO Abbreviation: Biol Rev Camb Philos Soc Publication Date: 2008 May |
Date Detail:
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Created Date: 2008-04-23 Completed Date: 2008-07-08 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 0414576 Medline TA: Biol Rev Camb Philos Soc Country: England |
Other Details:
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Languages: eng Pagination: 119-40 Citation Subset: IM |
Affiliation:
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Department of Biological Sciences, Brock University, St. Catharines, Ontario, L2S 3A1, Canada. gtatters@brocku.ca |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Acclimatization Adaptation, Physiological* Animals Anoxia / veterinary Basal Metabolism / physiology Cold Temperature* Energy Metabolism / physiology Female Hibernation / physiology* Immersion Male Oxygen / metabolism* Ranidae / metabolism, physiology* Species Specificity |
| Chemical | |
Reg. No./Substance:
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7782-44-7/Oxygen |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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