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Maternal costs of reproduction in the southern snow skink, Niveoscincus microlepidotus


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Kabat, AP 1999 , 'Maternal costs of reproduction in the southern snow skink, Niveoscincus microlepidotus', Honours thesis, University of Tasmania.

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Viviparous reproduction is associated with many potential costs that may contribute
to the need to adopt a number of physiological and behavioral tradeoffs. Costs are
divided into two main categories, survival and fecundity, and these may manifest as
locomotory, thermoregulatory, and metabolic costs. Animals must balance these costs
with the benefits of reproduction to evolve a successful life-history. To increase our
understanding of the life-histories of viviparous reptiles, this study investigated the
changes in mobility, thermoregulatory behavior, thermal physiology, and metabolism
during pregnancy in Niveoscincus microlepidotus.
Niveoscincus microlepidotus is a small (3 - 5g) alpine specialist, restricted to altitudes
above 1080 m in Tasmania, Australia. Its preferred microhabitat is open heathlands,
alpine forests, and dolerite boulder-fields. This species has an unusual reproductive
cycle that makes it an ideal study species for this type of study. Ovulation and mating
occur in spring to early summer, gestation takes place during summer and early
autumn. The fully developed embryos are held through the winter hibernation and
parturition occurs the following spring. Mating does not occur until the next spring.
This biennial reproductive mode allows pregnant and non-pregnant females to be
studied simultaneously.
This study has shown that female Niveoscincus microlepidotus decrease body
temperature during pregnancy. Presumably, this is in order to slow embryonic
development until just prior to the commencement of hibernation. This may have
substantial advantages for reducing the costs of pregnancy to the pregnant female and
any costs to the neonates.
It has also been shown that Niveoscincus microlepidotus incurs a significant decrease
in mobility during pregnancy, which is exaggerated by high temperature and therefore
increasing costs as gestation continues. However, it was also found that this species
may temporally shift its physiological optimal performance temperature to minimise the decrease in performance seen at higher temperatures. Many of the costs of
reproduction associated with impaired locomotory ability are thereby decreased ..
This study also examined changes in the standard metabolic rate (SMR) and active
metabolic rate (AMR) associated with viviparous pregnancy. This was accomplished
by measuring oxygen consumption for SMR and biological elimination of the
rubidium86 isotope for AMR. It was shown that there was a significant increase in
SMR that reached a peak in late pregnancy, and AMR was significantly higher in
pregnant females than non-pregnant females. This suggests that there is a significant
metabolic cost associated with pregnancy in female N. microlepidotus. The
rubidium86 isotope was proved to be a useful method for determining active metabolic
rates in the field, minimising many of the problems inherent in other radionucelotide
metabolic techniques.
This study has shown that Niveoscincus microlepidotus uses a range of physiological
and behavioral adaptations to minimise the costs of reproduction. Thereby, N.
microlepidotus has therefore evolved a successful life-history that has allowed it to
thrive in its variable alpine microhabitat.

Item Type: Thesis - Honours
Authors/Creators:Kabat, AP
Copyright Holders: The Author
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Copyright 1999 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
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