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Metabolism and temperature regulation in Marsupials with particular reference to the potoroo, potorous tridactylus apicalis Gould.

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Nicol, Stewart Charles 1978 , 'Metabolism and temperature regulation in Marsupials with particular reference to the potoroo, potorous tridactylus apicalis Gould.', PhD thesis, University of Tasmania.

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Abstract

In an attempt to clarify aspects of thermoregulation and
metabolism in marsupials a detailed investigation was made of the
potoroo.
Measurements of activity, oxygen consumption, creatinine
excretion and total urinary nitrogen excretion of potoroos were made
over 24 hour periods at a range of environmental temperatures.
Basal oxygen consumption was in agreement with previous observations
which have been made on this and other marsupial species, while the
rate of creatinine excretion appeared to be higher than in other
marsupials. Nitrogen metabolism did not appear to be related to
ambient temperature or total oxygen consumed.
Total serum thyroxine (TT4) and effective thyroxine ratio (ETR)
were measured in 12 potoroos. Although TT4 was low compared with
eutherians, the ETR suggested that free thyroxine concentrations were
equivalent to normal human levels.
Using a barometric technique tidal volume (VT), minute volume
(VE), respiratory frequency (f) and respiratory evaporative heat loss
(Eex) were measured from potoroos, barred bandicoots and laboratory
ex rabbits at temperatures in and above the thermoneutral zone (TNZ).
Rectal temperature (Tre) and oxygen consumption (V02) were also measured.
VT initially decreased with rising ambient temperature (Ta)
but in the potoroo and rabbit it then increased past the resting level.
VE increased much more in the marsupials than in the rabbit and higher
Eex maxima were also found for the marsupials. The marsupials had a
mean panting efficiency of 80% while the rabbits had a panting efficiency
of 100%.
Non-shivering thermogenesis (NST) was investigated in potoroos
by the injection of catecholamines. Calorigenic potencies at
thermoneutrality were isoprenaline >adrenaline> noradrenaline;
the increase in vo2 produced by these drugs being blocked by propranolol
but not by phenoxybenzamine. As the rise in vo2 due to injection of
noractrenaline was significantly less at 17°C than at 29°c the
potoroo must utilize NST in the cold.
To further investigate the metabolic status of marsupials water
turnover rates of Tasmanian devils were measured under standardised
conditions using tritiated water. Total body water of lactating
females was lower than in non-lactating animals, while water turnover
rates per kg were not significantly different due to a higher rate
constant for lactating animals. Mean water turnover rates were
considerably higher than predicted from other marsupial studies;
statistical analysis of this plus data published from 13 species of
marsupial and 27 eutherian species showed habitat to have a far greater
effect on standard water turnover rate than phylogenetic differences.
A similar statistical analysis was performed on vo2 and Tre data from 30
marsupial species and 34 eutherian species to investigate whether
differences between the two groups might be attributable to
habitat differences. This showed that the BMR of marsupials as a
group is significantly lower than that of eutherians even when animals
from similar habitats are compared.

Item Type: Thesis - PhD
Authors/Creators:Nicol, Stewart Charles
Keywords: Marsupials, Potoroos, Body temperature
Copyright Holders: The Author
Copyright Information:

Copyright 1978 the author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (Ph.D.)--University of Tasmania,. References : l. 123-159

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