Thermoregulation in monotremes: Riddles in a mosaic

Brice, PH (2009) Thermoregulation in monotremes: Riddles in a mosaic. AUSTRALIAN JOURNAL OF ZOOLOGY, 57 3-4: 255-263. doi:10.1071/ZO09039

Author Brice, PH
Title Thermoregulation in monotremes: Riddles in a mosaic
Journal name AUSTRALIAN JOURNAL OF ZOOLOGY   Check publisher's open access policy
ISSN 0004-959X
Publication date 2009-10
Year available 2009
Sub-type Article (original research)
DOI 10.1071/ZO09039
Volume 57
Issue 3-4
Start page 255
End page 263
Total pages 9
Editor Mark Elgar
Place of publication Australia
Publisher CSIRO Publishing
Collection year 2010
Language eng
Subject C1
9608 Flora, Fauna and Biodiversity
060809 Vertebrate Biology
Formatted abstract
The three extant genera of the Monotremata have evolved, probably from a pre-Cretaceous Gondwanan origin, independently of the Theria to display a variety of ancestral and derived features. A comparison of their thermoregulation reveals a diversity of physiology that might represent both plesiomorphic and apomorphic elements within this mosaic. In the tachyglossids, the echidnas Tachyglossus and Zaglossus, body temperature is often labile, rising as a result of activity and allowed to decline during inactivity. This daily heterothermy, which is not necessarily torpor, may combine with typical mammalian hibernation to provide substantial energy economy in a wide variety of often unproductive habitats. Only when incubating do free-ranging echidnas display classic mammalian thermoregulation, the facultative nature of which suggests echidna-like physiology as an example of a protoendothermic stage in the evolution of endothermy. Similarly, physiological response to heat in Tachyglossus, at least, may be plesiomorphic, relying on the cyclic loss of heat stored during activity. Tachyglossids neither exhibit a panting response nor spread saliva to facilitate evaporative cooling and Tachyglossus, though not Zaglossus, lacks functional sweat glands. By contrast, the only extant ornithorhynchid, the platypus Ornithorhynchus, does not utilise heterothermy of any kind and maintains its body temperature more tightly than several semiaquatic eutherians. Although not necessarily required, it responds to heat via sweating, but not panting or saliva spreading. The classic nature of ornithorhynchid thermoregulation stands in marked contrast to the more diverse thermoregulatory responses shown by the tachyglossids, making it difficult to determine which aspects of monotreme thermoregulation are plesiomorphic and which are apomorphic.
Q-Index Code C1
Q-Index Status Confirmed Code

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2010 Higher Education Research Data Collection
School of Biological Sciences Publications
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Citation counts: TR Web of Science Citation Count  Cited 9 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 10 times in Scopus Article | Citations
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Created: Mon, 23 Nov 2009, 15:25:26 EST