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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

THE ENVIRONMENTAL AND MUSCLE PHYSIOLOGY OF WINTER-ACTIVE AND WINTER-INACTIVE LIZARDS, SCELOPORUS JARROVI AND SCELOPORUS MAGISTER

Schwalbe, Cecil Robert January 1981 (has links)
Field observations indicated a difference in the ability to locomote at low body temperatures in two closely related species of lizards from very different habitats and with radically different seasonal behavior. I measured the critical thermal minimum (the body temperature at which a cooling lizard just loses the ability to right itself) in both species. The winter-active, montane Sceloporus jarrovi had a significantly lower critical thermal minimum in both summer and winter than the winter-hibernating, lowland S. magister. Critical thermal minima were significantly lower in winter than in summer for both species. To determine a physiological basis for these differences, I examined the activity of myosin ATPase, which plays the limiting role in the velocity of muscle contraction, and the energetics of muscle as reflected by high energy phosphate compounds. Microenvironmental conditions were correlated with behavior, constraints on winter activity, and muscle physiology. Ca²⁺-activated myosin ATPase activity in S. magister of valley bottoms is greater than that in the vertical rock-dwelling S. jarrovi. No seasonal acclimatization occurs in myosin ATPase activity in either species. Changes in the muscle metabolism of hibernating animals has been attributed to the lack of muscular contractions in the dormant animals. I measured levels of phosphorylated compounds in a hindlimb muscle from summer and winter lizards of both species. Significant seasonal changes occur in some of the phosphate compounds in both species even though, within a given season, respective levels of phosphorylated compounds are similar in both species. Phosphorylcreatine and total acid-soluble phosphate levels increased in winter animals of both species. Apparently the high levels of phosphorylcreatine in winter S. magister are not simply due to inactivity; winter-active S. jarrovi contain similar amounts. Seasonal cycling of phosphate compounds may relate more to parathyroid status than to muscle activity. Winter activity in S. jarrovi was site-specific and highly dependent on a favorable microclimate. Winter dormancy in S. magister apparently is not dictated by the severity of the microclimate nor physiological limitations of skeletal muscle, but may be strongly influenced by the thermal inertia of that relatively large species.
112

Lizards as a model system for investigating environmental change

Tull, John Christopher. January 2006 (has links)
Thesis (Ph. D.)--University of Nevada, Reno, 2006. / "May 2006." Includes bibliographical references. Online version available on the World Wide Web.
113

An experimental study of juvenile competition and habitat niche partitioning between a native lizard (Anolis carolinensis) and an introduced congener (Anolis sagrei) in the southeastern United States

Walguarnery, Justin W., January 2008 (has links) (PDF)
Thesis (Ph. D.)--University of Tennessee, Knoxville, 2008. / Title from title page screen (viewed on Sept. 10, 2009). Thesis advisor: Arthur C. Echternacht. Vita. Includes bibliographical references.
114

Variação sazonal da temperatura corpórea no lagarto Teiú, Tupinambis merianae (Squamata, Lacertilia, Teiidae)

Ribas, Elis Regina [UNESP] 10 May 2005 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:30:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-05-10Bitstream added on 2014-06-13T20:20:35Z : No. of bitstreams: 1 ribas_er_me_rcla.pdf: 879410 bytes, checksum: 106cf54738d28c7d4233bc6e3591f98c (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Com o propósito de obter um perfil da variação sazonal e diária da temperatura corpórea (Tc) do lagarto teiú, T. merianae, sensores/ registradores de temperatura (data-loggers) foram cirurgicamente implantados, em oito espécimes adultos de ambos os sexos.Os lagartos foram mantidos em baias ao ar livre e acompanhados durante um ano. As temperaturas dos microambientes ao sol, na sombra e na toca foram igualmente registradas. A Tc dos teiús mostrou variação sazonal e diária relacionadas às mudanças nas temperaturas dos microambientes e aos ajustes fisiológicos nas taxas de aquecimento e de resfriamento. A Tc média diária seguiu um ritmo circadiano, com temperaturas mínimas no início da manhã, aumento entre 12h e 16h e queda gradual ao final da tarde. A Tc media diária de atividade durante a estação de atividade (agosto/dezembro) ficou em 33,6oC l 1,4 oC. A taxa média de aquecimento foi cinco vezes maior que a de resfriamento durante a estação de atividade, o que permitiu ao animal manter sua Tc acima da temperatura do abrigo e da sombra. Com o declínio da temperatura ambiente em meados do outono, os teiús entram nos abrigos e o ritmo circadiano de variação da Tc diminuiu. Durante a estação de dormência, a Tc máxima diária foi de 20,1oC l 0,7oC e seguiu a variação térmica do abrigo. Durante a estação de atividade, T. merianae controla sua Tc por termorregulação. Nos meses frios o teiú entra em dormência com a queda da Tc, que acompanha passivamente a temperatura da toca. / In order to obtain a profile of the seasonal and daily variation of the body temperature (Tc) of the tegu lizard, Tupinambis merianae, TidBit® electronic data loggers (temperature probes) were surgically implanted in eight adult individuals. The lizards were kept in outdoor pens and monitored over a one year period. Teguþs body temperature showed seasonal and daily variations, which were related to the changes in the temperatures of the microhabitats (sun, shade, and burrow) and, possibly, to changes in heating and cooling rates. The daily average Tc followed a circadian rhythm characterized by lowest temperatures occurring at dawn, then temperature rapidly increases from soon after sunrise until noon, Tc is then maintained in high levels until late afternoon (~16h) when the lizards stop activity, retreat to the burrow, and let body temperature to drop. The mean Tc experienced by the tegus during activity at the warm season (August/December) was 33.6 oC l 1,4 oC. During the active season, the heating rate of the lizards during the morning was five times greater than the cooling rate experienced during the night. As a result, tegus seems to be able to maintain their Tc above the temperature of the burrow and of the shade along the night time. With declining air temperatures towards the end of autumn, tegus enter their burrows, goes into dormancy, and the circadian rhythm in Tc become less prominent. During this season, Tc followed passively the variation of the burrowþs temperature.
115

Fetal Nutrition in Lecithotrophic Squamate Reptiles: Toward a Comprehensive Model for Evolution of Viviparity and Placentation

Stewart, James R. 01 July 2013 (has links)
The primary pattern of embryonic nutrition for squamate reptiles is lecithotrophy; with few exceptions, all squamate embryos mobilize nutrients from yolk. The evolution of viviparity presents an opportunity for an additional source of embryonic nutrition through delivery of uterine secretions, or placentotrophy. This pattern of embryonic nutrition is thought to evolve through placental supplementation of lecithotrophy, followed by increasing dependence on placentotrophy. This review analyzes the relationship between reproductive mode and pattern of embryonic nutrition in three lecithotrophic viviparous species, and oviparous counterparts, for concordance with a current model for the evolution of viviparity and placentation. The assumptions of the model, that nutrients for oviparous embryos are mobilized from yolk, and that this source is not disrupted in the transition to viviparity, are supported for most nutrients. In contrast, calcium, an essential nutrient for embryonic development, is mobilized from both yolk and eggshell by oviparous embryos and reduction of eggshell calcium is correlated with viviparity. If embryonic fitness is compromised by disruption of a primary source of calcium, selection may not favor evolution of viviparity, yet viviparity has arisen independently in numerous squamate lineages. Studies of fetal nutrition in reproductively bimodal species suggest a resolution to this paradox. If uterine calcium secretion occurs during prolonged intrauterine egg retention, calcium placentotrophy evolves prior to viviparity as a replacement for eggshell calcium and embryonic nutrition will not be compromised. This hypothesis is integrated into the current model for evolution of viviparity and placentation to address the unique attributes of calcium nutrition. The sequence of events requires a shift in timing of uterine calcium secretion and the embryonic mechanism of calcium retrieval to be responsive to calcium availability. Regulation of uterine calcium secretion and the mechanism of embryonic uptake of calcium are important elements to understanding evolution of viviparity and placentation.
116

Fetal Nutrition in Lecithotrophic Squamate Reptiles: Toward a Comprehensive Model for Evolution of Viviparity and Placentation

Stewart, James R. 01 July 2013 (has links)
The primary pattern of embryonic nutrition for squamate reptiles is lecithotrophy; with few exceptions, all squamate embryos mobilize nutrients from yolk. The evolution of viviparity presents an opportunity for an additional source of embryonic nutrition through delivery of uterine secretions, or placentotrophy. This pattern of embryonic nutrition is thought to evolve through placental supplementation of lecithotrophy, followed by increasing dependence on placentotrophy. This review analyzes the relationship between reproductive mode and pattern of embryonic nutrition in three lecithotrophic viviparous species, and oviparous counterparts, for concordance with a current model for the evolution of viviparity and placentation. The assumptions of the model, that nutrients for oviparous embryos are mobilized from yolk, and that this source is not disrupted in the transition to viviparity, are supported for most nutrients. In contrast, calcium, an essential nutrient for embryonic development, is mobilized from both yolk and eggshell by oviparous embryos and reduction of eggshell calcium is correlated with viviparity. If embryonic fitness is compromised by disruption of a primary source of calcium, selection may not favor evolution of viviparity, yet viviparity has arisen independently in numerous squamate lineages. Studies of fetal nutrition in reproductively bimodal species suggest a resolution to this paradox. If uterine calcium secretion occurs during prolonged intrauterine egg retention, calcium placentotrophy evolves prior to viviparity as a replacement for eggshell calcium and embryonic nutrition will not be compromised. This hypothesis is integrated into the current model for evolution of viviparity and placentation to address the unique attributes of calcium nutrition. The sequence of events requires a shift in timing of uterine calcium secretion and the embryonic mechanism of calcium retrieval to be responsive to calcium availability. Regulation of uterine calcium secretion and the mechanism of embryonic uptake of calcium are important elements to understanding evolution of viviparity and placentation.
117

Multi-functional Foot Use While Running Across Complex Terrain

Tucker, Elizabeth, 0000-0002-4831-7571 January 2022 (has links)
Running on land is fraught with challenges. Changes in topography, material properties, and the general heterogeneity of terrain necessitate the ability to sense, process, and compensate for changes quickly and repeatedly. Failure to do so successfully has potentially fatal consequences on an animal’s survival. I used lizards as an experimental model to examine how animals move successfully across complex terrain, because they are found in a vast range of habitat types and have a foot shape conserved across many families. I found that sprawled running appears to confer surprising robustness against large surface drops without any decrease in running speed, through the interplay between changes in body and limb posture. Increased combinations of foot placement and positioning result in more stable solutions than are otherwise possible among animals with erect limb postures. Using high-speed x-ray to visualize subsurface foot motion while running on sand, I discovered that lizards often found on fine sand spread their toes to distances known to maximize particle-particle interactions for force production on sand. Finally, I used a hopping robot outfitted with 3-D printed bio-inspired feet to show that the toe spacing pattern used by sand specialist lizards increases jump height for both stiff and flexible foot models. In summary, this work illuminates how adaptations for complex terrain may not be largely driven by selection for foot shape, but rather through modifications of behavior and functional morphology which likely confer robustness during locomotion across a variety of terrain. / Biology
118

The ecology and life history of sceloporus occidentalis longipes baird on Rainier Mesa at Nevada test site

Hopkin, James Mark 01 August 1968 (has links)
The study was undertaken to learn the life history of Sceloporus occidentalis longipes and its environmental adaptations on a high plateau (Rainier Mesa) with an elevation of 2,286 meters, at the Atomic Energy Commission's Nevada Test Site in Nye County, Nevada. The lizards emerge from hibernation in April with the males preceeding the females by a period of one to two weeks or more. Mating occurs in late April, May, and perhaps early June. Eggs are laid between 10 June and 15 July. Clutches of 9 to 15 eggs are laid with the younger females usually laying 9 eggs. No eggs were found in the field.
119

A comparative study of the head and thoracic osteology and myology of the skinks, Eumeces gilberti Van Denburgh and Eumeces skiltonianus (Baird and Girard)

Nash, David F. 28 July 1970 (has links)
Further clarification of the taxonomic and phylogenetic relationships of Eumeces gilberti and Eumeces skiltonianus is achieved by the comparisons of the skull, mandible elements, and the anterior myology of these two species. Figures are provided to compliment the descriptions. The study confirms their close relationship and few differences are observed. E. skiltonianus, however, appears to have more anatomical plasticity which suggests that E. gilberti may have arisen from the former.
120

Comparative Studies in the Functional Morphology of Lizard Feeding: Kinematics, Behavior, and Biomechanics

McBrayer, Lance D. 12 November 2002 (has links)
No description available.

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