Show simple item record

dc.contributor.authorvan Doorn, Kevin
dc.date.accessioned2012-12-12 18:06:25 (GMT)
dc.date.available2012-12-12 18:06:25 (GMT)
dc.date.issued2012-12-12T18:06:25Z
dc.date.submitted2012
dc.identifier.urihttp://hdl.handle.net/10012/7148
dc.description.abstractThe 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.en
dc.language.isoenen
dc.publisherUniversity of Waterlooen
dc.subjectreptilian spectacleen
dc.subjectspectral transmittanceen
dc.subjectspectral transmissionen
dc.subjectkeratinen
dc.subjectbeta keratinen
dc.subjectsnakeen
dc.subjectgeckoen
dc.subjectblood flowen
dc.subjectcoachwhip snakeen
dc.subjectMasticophis flagellumen
dc.subjectß keratinen
dc.subjectvascular dynamicsen
dc.titleInvestigations on the Reptilian Spectacleen
dc.typeDoctoral Thesisen
dc.pendingfalseen
dc.subject.programVision Science and Biologyen
uws-etd.degree.departmentSchool of Optometryen
uws-etd.degreeDoctor of Philosophyen
uws.typeOfResourceMoving Imageen
uws.typeOfResourceTexten
uws.peerReviewStatusUnrevieweden
uws.scholarLevelGraduateen


Files in this item

Thumbnail
Thumbnail
Thumbnail

This item appears in the following Collection(s)

Show simple item record


UWSpace

University of Waterloo Library
200 University Avenue West
Waterloo, Ontario, Canada N2L 3G1
519 888 4883

All items in UWSpace are protected by copyright, with all rights reserved.

DSpace software

Service outages