Thermal control of delivery date and resulting offspring condition in a viviparous gecko
|dc.contributor.author||Moore, Georgia Agnes|
|dc.identifier.citation||Moore, G. A. (2015). Thermal control of delivery date and resulting offspring condition in a viviparous gecko (Thesis, Master of Science). University of Otago. Retrieved from http://hdl.handle.net/10523/5924||en|
|dc.description.abstract||While many viviparous squamates complete embryogenesis and give birth to offspring soon afterwards, a small number of species show a greater plasticity in their reproductive timing. Such species may complete development of embryos and either deliver them shortly afterwards, or if environmental conditions are not optimal, retain fully-developed embryos in utero through winter, delivering them the following spring. Cues that trigger the birth process in these species are, therefore, likely to be environmental rather than endogenous. While the benefits of flexibility in reproductive frequency have been theorised and investigated, the mechanism of environmental cues for parturition has been largely overlooked. In this thesis, the Otago-Southland gecko (Woodworthia “Otago-Southland”) was used as a model to examine the effects of two thermal factors on season of parturition, in order to determine their possible function as environmental birth cues. I exposed 60 late-pregnant females to combinations of different levels of daytime basking opportunity and night temperature in the laboratory, and recorded their responses in terms of birth season and delivery date. Offspring characteristics including body size, condition and growth rate were also measured. Finally, changes in maternal temperature preference between late-pregnancy and following birth were measured and compared with temperature preferences of offspring at birth. I found that Otago-Southland geckos use basking opportunity in the laboratory as a trigger for parturition, giving birth in autumn if basking opportunity is sufficiently high, and otherwise holding offspring in utero throughout winter to deliver in spring. Offspring born in different seasons showed significant differences in body mass and condition, though initial growth rates in the laboratory were the same in each group. Mothers displayed a significant rise in selected temperature following birth, suggesting that altered preferences during late-pregnancy may occur for the benefit of developing offspring. The results of my thesis suggest that increases in cloud cover (i.e. reduction of basking opportunity) could lead to annually-reproducing populations of Otago-Southland geckos switching to biennial reproduction. My thesis adds to the as-yet small amount of knowledge on the use on environmental cues for birth in viviparous squamates with flexible reproductive frequency.|
|dc.publisher||University of Otago|
|dc.rights||All items in OUR Archive are provided for private study and research purposes and are protected by copyright with all rights reserved unless otherwise indicated.|
|dc.title||Thermal control of delivery date and resulting offspring condition in a viviparous gecko|
|thesis.degree.name||Master of Science|
|thesis.degree.grantor||University of Otago|
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