Literaturdatenbank
Literaturdatenbank |
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Beggs, K. E. (1998). Embryonic development of the pig-nosed turtle, carettochelys insculpta, under constant and fluctuating temperature regimes. Unpublished thesis , University of Canberra.
Added by: Admin (06 Jan 2014 18:22:38 UTC) |
| Resource type: Thesis/Dissertation BibTeX citation key: anon1998a View all bibliographic details  |
Categories: General Keywords: Carettochelyidae, Carettochelys insculpta, Chelydra serpentina, Chelydridae, Schildkröten - turtles + tortoises, Zeitigung - incubation Creators: Beggs Publisher: University of Canberra |
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| Abstract |
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This study examined the embryonic development of Carettochelys insculpta, under constant and fluctuating temperature regimes, involving artificial incubation and natural nests. The study aimed to enhance our understanding of C. insculpta embryology and develop methods of ageing embryos from both candling attributes and embryo characteristics. Research was also undertaken to establish the relationships between soil depth, temperature regime and rates of embryonic development. Our ability to model development using incubation temperatures was also evaluated. Two highly effective methods of ageing embryos were developed in this study, during constant temperature incubation experiments at 30°C. Qualitative observations and measurements of candling attributes were found to be useful for ageing C. insculpta embryos, particularly during the early to mid stages of development (i.e. all but between 2.5 and 8 days, and after 52 days of incubation). The detailed candling ageing system developed during this study is, to date, the only non-destructive method available for ageing reptilian embryos. Ageing was also possible from the direct examination of embryos, using a developmental series based on that of Chelydra serpentina, provided morphological differences between the species were taken into account. Strong predictive relationships between embryonic size, age and stage as valuable tools for ageing. A method for adjusting the 30oC ageing work for the effect of incubation temperature on development is presented. Relationships between candling attributes, embryo morphometrics, embryonic stage and age established during the study are therefore applicable to eggs and embryos from a range of incubation environments. Variation in thermal regime with soil depth was demonstrated during this study. They differed mainly in the magnitude of daily fluctuations and timing of maximum and minimum temperature. However, mean temperatures were generally similar at all depths. The observed variations in thermal regime did not cause developmental asynchrony in C. insculpta embryos. This challenges current accepted hypotheses regarding variations in thermal regime and developmental asynchrony. Lastly, this study demonstrated that C. insculpta embryonic development in field nests and artificial cyclic incubation experiments could be satisfactorily predicted from incubation temperatures using a linear development model. However, the model predictions were most accurate when the time of maximum development was considered to occur at stage 24, and when thermal conditions were not too hot (i.e less than 36°C). In short, the findings of this study have made an important contribution to the descriptive developmental embryology of the pig-nosed turtle, Carettochelys insculpta. This research has also contributed to reptilian embryology, in general, through the development of a non-destructive ageing technique. Furthermore, this study has improved our understanding of and ability to model the thermal influences on reptilian embryonic development, under constant and fluctuating temperatures.
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