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4.4.4 Conclusion This research was inspired by the variation observed in the spectral transmission results reported in Chapter 3. While no direct link between keratin content and spectral transmission could be made, the results do indicate that the composition of the spectacle scale is different from other scales, both in snakes and in geckos. Furthermore, the variation in the ß keratin content of spectacle scales of different species and families indicates that transparency is not restricted to a single ß keratin or isoform, but rather that ß keratins in general, as well as α keratins, may have the potential of achieving transparency. 103
Chapter 5, Summary and Concluding Remarks Though minuscule in area compared with the whole of the integument, the reptilian spectacle presents numerous specializations of the skin to permit acute vision while still maintaining the integument’s protective role. The research presented in this thesis covered two such specializations: (1) the vascular dynamics that act to minimize the effect of the spectacle vasculature in the visual field, and (2) the transparent scale that has a different composition than scales elsewhere on the integument and in some cases exhibits potentially adaptive transmittance spectra. The spectacle vasculature presents a unique visual problem in that no other known vertebrate (manatees excepted; Harper et al. 2005) has blood vessels in the optically transmissive portions of the eye other than the retina. What’s more, the eyes of spectacled reptiles rotate freely beneath their spectacles, causing shifts in the location of the vessels within the visual field, which would interfere with adaptation (Troxler 1804; Lettvin et al. 1968). Lüdicke’s (1969) finding of the asymmetry of Ahaetulla nasuta’s spectacle vasculature and Mead’s (1976) finding of the vessel walls being transparent, just as are retinal blood vessel walls (Martin 2009), further reinforce the supposition that the spectacle vessels can be detrimental to vision (from an unspectacled species’ perspective) and hint at the evolutionary tweaking that’s taken place to maximize spectacled animals’ visual clarity. Cutaneous vasculature is especially apt at regulating flow via vasomotor mechanisms (Fredericq 1882; Hertzman 1959; Fox and Edholm 1963; Kellogg Jr. 2006), leading one to wonder if the spectacle blood vessels may react to endogenous or exogenous stimuli and if such stimuli were to induce constriction of the vessels, all visual problems might be solved (for a time). The results presented in Chapter 2 demonstrated that a neural mechanism does exist to enable spectacle vessels to constrict when a sympathetic response is incurred. The potential for future research is certainly not lacking, as the results raise several interesting questions on the mechanism involved and its prevalence among spectacled species. Is the mechanism observed in snakes comparable across species, whether highly visual (eg. A. nasuta) or not (eg. blind snakes)? Is the mechanism present in species with windowed eyelids? Is the mechanism engaged only when faced by a perceived threat to facilitate defensive and 104
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Investigations on the Reptilian Spe
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Abstract The eyes of snakes and mos
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Heritage Library, Smithsonian Libra
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2.2.1 Animals 36 2.2.2 Experimental
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List of Figures 1-1. The earliest a
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List of Tables 2-1. Durations of sp
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UV-A Ultraviolet A (315-400 nm) UV-
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“Il est de connaissance presque v
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1.1 Anatomy of the spectacle The si
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corneum, 2- an inner stratum corneu
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The two layers he described in the
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Figure 1-5. Illustration of the spe
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injected spectacles clearly shows t
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Figure 1-8. In vivo confocal micros
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1.1.3 The Spectacles of Geckos Most
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1.1.4 The Spectacles of Amphisbaeni
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Gymnophthalmus (spectacled tegus) a
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appreciates on observing the sadly
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hydration state (van Doorn, unpubl.
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1.5 Adaptive Significance of the Sp
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diurnally active in hot and dry hab
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of his argument hinges on the prese
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• In Chapter 3, findings on the v
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2.1 Introduction This introduction
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2.2 Methods & Materials The experim
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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
Page 65 and 66: Chapter 3, Spectral Transmission of
Page 67 and 68: like the cornea, may exhibit simila
Page 69 and 70: The scales of both the right and le
Page 71 and 72: Figure 3-1. Spectral transmittance
Page 73 and 74: % Transmittance % Transmission % Tr
Page 75 and 76: % % Transmittance Transmission % %
Page 77 and 78: λ 50% (nm) 420 400 380 360 340 320
Page 79 and 80: Thickness (!m) Figure 3-7. Plot of
Page 81 and 82: Family Spearmanʼs rho p Colubridae
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Page 87 and 88: Another potential factor that may g
Page 89 and 90: Colubridae Colubrinae Elaphe taeniu
Page 91 and 92: Pythonidae Python sebae Rock Python
Page 93 and 94: 4.1 Introduction The reptilian spec
Page 95 and 96: thus be optimized to meet not only
Page 97 and 98: 4.2 Methods & Materials 4.2.1 Sampl
Page 99 and 100: for 15 minutes to remove all residu
Page 101 and 102: 4.3 Results 4.3.1 Keratins of Coach
Page 103 and 104: 24 kDa > 17 kDa > 12 kDa > S1 P1 V1
Page 105 and 106: 76 kDa > 52 kDa > 24 kDa > 17 kDa >
Page 107 and 108: 31 kDa > 24 kDa > 17 kDa > 12 kDa >
Page 109 and 110: 4.3.4 2D Electrophoretic Comparison
Page 111 and 112: kDa 76 - 52 - 38 - 31 - 24 - 17 - 1
Page 113 and 114: (2007a) have theorized that basic
Page 115: spectacle, this layer may be partic
Page 119 and 120: evaluations of the elastic modulus
Page 121 and 122: References Addison WHF, How HW. 192
Page 123 and 124: Berkley MA, Wakins DW. 1973. Gratin
Page 125 and 126: Chou BR, Hawryshyn CW. 1987. Spectr
Page 127 and 128: Fox RH, Edholm OG. 1963. Nervous co
Page 129 and 130: Hinkley JA, Savitsky AH, River G, G
Page 131 and 132: Lee P, Wang CC, Adamis AP. 1998. Oc
Page 133 and 134: Mautz WJ. 1982. Patterns of evapora
Page 135 and 136: Rice GE, Bradshaw SD. 1980. Changes
Page 137 and 138: Sillman AJ, Govardovskiĭ WI, Röhl
Page 139 and 140: Valentin G. 1879a. Ein Beitrag zur
Page 141 and 142: Appendix A One cycle of spectacle b
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