Chapter 1, The Reptilian Spectacle - UWSpace - University of ...

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$uWaterloo LaTeX Thesis Template - UWSpace - University of Waterloo$

AUTHOR'S DECLARATION I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. ii
Abstract The eyes of snakes and most geckos, as well as a number of other disparate squamate taxa, are shielded beneath a layer of transparent integument referred to as the “reptilian spectacle.” Derived from the embryonic fusion of palpebral tissues, the spectacle contains a number of specializations of the skin to benefit vision while still allowing it to function as the primary barrier to the environment. For example, in nearly all species that possess it, it is markedly thinned compared to the surrounding integument and its keratinized scale is optically transparent. While the spectacle may thus seem ideally adapted to vision in allowing the eyes to be always unoccluded, it does have a few drawbacks. One such drawback is its vascularity, the implications of which are still not fully understood, but are explored herein. As no recent synthesis exists of the body of knowledge on reptilian spectacles, the first chapter of this thesis consists of a review of spectacle anatomy, physiology, adaptive significance and evolution to help put into context the following chapters that present original research. The second chapter describes the dynamics of blood flow through the spectacle vasculature of colubrid snakes, demonstrating three main points: (1) that the spectacle vasculature exhibits cycles of regular dilation and constriction, (2) that the visual perception of a threat induces vasoconstriction of its vessels, and (3) that spectacle vessels remain dilated throughout the renewal phase. The implications of these points are discussed. The third chapter describes the spectral transmittance of the shed spectacle scale, the only keratinized structure in the animal kingdom to contribute to the dioptric apparatus of the eye, as well as its thickness. Spectacle scale transmittance and thickness was found to differ dramatically between snakes and geckos and found in snakes to vary between families. The adaptive significance of the observed variation is discussed. The fourth chapter describes biochemical analyses of the shed spectacle scales of snakes and geckos and compares their composition to other scales in the integument. Spectacle scales were found to differ significantly from other scales in their keratin composition, and gecko spectacle scales in particular were found to lack ß keratin, that hard corneous protein thought to be common to all reptile scales. The concluding chapter will discuss where this research has brought the state of our knowledge on the spectacle and offers thoughts on potentially useful avenues for further research. iii
Page 1: Investigations on the Reptilian Spe
Page 5 and 6: Heritage Library, Smithsonian Libra
Page 7 and 8: 2.2.1 Animals 36 2.2.2 Experimental
Page 9 and 10: List of Figures 1-1. The earliest a
Page 11 and 12: List of Tables 2-1. Durations of sp
Page 13 and 14: UV-A Ultraviolet A (315-400 nm) UV-
Page 15 and 16: “Il est de connaissance presque v
Page 17 and 18: 1.1 Anatomy of the spectacle The si
Page 19 and 20: corneum, 2- an inner stratum corneu
Page 21 and 22: The two layers he described in the
Page 23 and 24: Figure 1-5. Illustration of the spe
Page 25 and 26: injected spectacles clearly shows t
Page 27 and 28: Figure 1-8. In vivo confocal micros
Page 29 and 30: 1.1.3 The Spectacles of Geckos Most
Page 31 and 32: 1.1.4 The Spectacles of Amphisbaeni
Page 33 and 34: Gymnophthalmus (spectacled tegus) a
Page 35 and 36: appreciates on observing the sadly
Page 37 and 38: hydration state (van Doorn, unpubl.
Page 39 and 40: 1.5 Adaptive Significance of the Sp
Page 41 and 42: diurnally active in hot and dry hab
Page 43 and 44: of his argument hinges on the prese
Page 45 and 46: • In Chapter 3, findings on the v
Page 47 and 48: 2.1 Introduction This introduction
Page 49 and 50: 2.2 Methods & Materials The experim
Page 51 and 52: To allow for extended high-magnific
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At 30 minutes into the experiment,
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packages. All statistical analyses
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2.3 Results 2.3.1 Spectacle blood f
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Figure 2-7. Graph of two representa
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2.4 Discussion The purpose of this
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vascular changes were occurring onl
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Chapter 3, Spectral Transmission of
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like the cornea, may exhibit simila
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The scales of both the right and le
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Figure 3-1. Spectral transmittance
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% Transmittance % Transmission % Tr
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% % Transmittance Transmission % %
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λ 50% (nm) 420 400 380 360 340 320
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Thickness (!m) Figure 3-7. Plot of
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Family Spearmanʼs rho p Colubridae
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virtue of both being characteristic
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nocturnal (Brattstrom 1952; Klauber
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Another potential factor that may g
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Colubridae Colubrinae Elaphe taeniu
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Pythonidae Python sebae Rock Python
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4.1 Introduction The reptilian spec
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thus be optimized to meet not only
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4.2 Methods & Materials 4.2.1 Sampl
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for 15 minutes to remove all residu
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4.3 Results 4.3.1 Keratins of Coach
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24 kDa > 17 kDa > 12 kDa > S1 P1 V1
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76 kDa > 52 kDa > 24 kDa > 17 kDa >
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31 kDa > 24 kDa > 17 kDa > 12 kDa >
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4.3.4 2D Electrophoretic Comparison
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kDa 76 - 52 - 38 - 31 - 24 - 17 - 1
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(2007a) have theorized that basic
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spectacle, this layer may be partic
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Chapter 5, Summary and Concluding R
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evaluations of the elastic modulus
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References Addison WHF, How HW. 192
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Berkley MA, Wakins DW. 1973. Gratin
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Chou BR, Hawryshyn CW. 1987. Spectr
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Fox RH, Edholm OG. 1963. Nervous co
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Hinkley JA, Savitsky AH, River G, G
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Lee P, Wang CC, Adamis AP. 1998. Oc
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Mautz WJ. 1982. Patterns of evapora
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Rice GE, Bradshaw SD. 1980. Changes
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Sillman AJ, Govardovskiĭ WI, Röhl
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Valentin G. 1879a. Ein Beitrag zur
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Appendix A One cycle of spectacle b
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