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1
Havens, Sarah Beth. „The role of skeletal development in body size evolution of two North American frogs“. Diss., Rolla, Mo. : Missouri University of Science and Technology, 2010. http://scholarsmine.mst.edu/thesis/pdf/Havens_2010_09007dcc807be556.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2010.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 7, 2010) Includes bibliographical references.
2
Tucker, Abigail Saffron. „Tail development in Xenopus laevis“. Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297296.
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3
Kulkarni, Saurabh S. „Endocrine Mechanisms Underlying Phenotypic Evolution in Frogs“. University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342106009.
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4
Schulze, Sabrine. „Wnt6 function in eye development in Xenopus laevis“. Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=192239.
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The eyes are the most important sensory organs for most vertebrates. Their structure and development is conserved between several vertebrate species. The development is regulated by several signalling pathways, including the Wnt/β-catenin signalling pathway. It is required for several aspects of retinal development and it is known to regulate the proliferation of neuro-epithelial stem cells. In Xenopus laevis the intracellular Wnt/β-catenin signalling pathway is activated in the retina by the Wnt receptor Fz5. Fz5 function in the eye was shown to regulate tissue specific gene expression and neuron versus Müller glial cell differentiation. However, no candidate Wnt ligand that could act through the Fz5 receptor in this tissue had been described. Wnt6 was recently found to be expressed in the developing retina, indicating that Wnt6 and Fz5 share temporal and spatial expression. Here, I tested the hypothesis that Wnt6 might function as ligand for Fz5 in the retina. In this thesis I show that a knock down of Wnt6 led to the same eye phenotype seen in Fz5 morphants, including reduced eye size, changed marker gene expression and altered neuron/Müller glia ratio. Rescue experiments show that the observed phenotype is specific and is mediated by altered Wnt/β-catenin signalling pathway function. These findings support a linear model, in which Wnt6 signal interacts with the Fz5 receptor to activate the Wnt/β-catenin pathway to regulate neural and Müller glia cell differentiation in retinal tissue. These results make Wnt6 a candidate for Fz5 ligand.
5
Wakefield, L. V. „Control of genes synthesizing small RNAs in amphibian development“. Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355661.
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6
Cheung, Ka-chun, und 張家進. „Roles of makorin-2 in embryonic development and carcinogenesis“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45595197.
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7
Lanctôt, Chantal. „The Effects of Glyphosate-based Herbicides on the Development of Wood Frogs, Lithobates sylvaticus“. Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23288.
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Amphibians develop in aquatic environments where they are very susceptible to the effects of pesticides and other environmental contaminants. Glyphosate-based herbicides are widely used and have been shown to affect survival and development of tadpoles under laboratory conditions. The goal my thesis is to determine if agriculturally relevant exposure to Roundup WeatherMax®, a herbicide formulation containing the potassium salt of glyphosate and an undisclosed surfactant, influences the survival and development of wood frogs tadpoles (Lithobates sylvaticus) under both laboratory and field conditions. In the field, experimental wetlands were divided in half using an impermeable curtain so that each wetland contained a treatment and control side. Tadpoles were exposed to two pulses of this herbicide at environmentally realistic concentration (ERC, 0.21 mg acid equivalent (a.e.)/L) and predicted environmental concentrations (PEC, 2.89 mg a.e./L), after which survival, growth, development, and expression of genes involved in metamorphosis were measured. Results indicate that exposure to the PEC is extremely toxic to tadpoles under laboratory conditions but not under field conditions. Results from both experimental conditions show sublethal effects on growth and development, and demonstrate that ERC of glyphosate-based herbicides have the potential to alter hormonal responses during metamorphosis. My secondary objectives were to compare the effects of Roundup WeatherMax® to the well-studied Vision® formulation (containing the isopropylamine (IPA) salt of glyphosate and POEA), and to determine which ingredient(s) are responsible for the sublethal effects on development. Survival, growth and gene expression results indicate that Roundup WeatherMax® has greater toxicity than Vision® formulation. Contrary to my prediction, results suggest that, under realistic exposure scenarios, POEA is not the sole ingredient responsible for the observed developmental effects. However, my results demonstrate that chronic exposure to the POEA surfactant at the PEC (1.43 mg/L) is extremely toxic to wood frog tadpoles in laboratory. As part of the Long-term Experimental Wetlands Area (LEWA) project, this research contributes to overall knowledge of the impacts of glyphosate-based herbicides on aquatic communities.
8
Wang, Yu. „HPLC method development for the evaluation of pheromones from the dwarf African clawed frog Hymenochirus“. Scholarly Commons, 2003. https://scholarlycommons.pacific.edu/uop_etds/587.
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9
Bouffard, Jeremie. „Effects of a Neonicotinoid Insecticide and Population Density on Behaviour and Development of Wood Frogs (Lithobates sylvaticus)“. Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42390.
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Amphibians have been facing global declines over the last decades due to direct and indirect effects of anthropogenic activities. One of the leading causes is environmental contamination, particularly that of waterbodies which are used by many amphibian species for reproduction, development, and adult life. An important source of contamination comes from agricultural runoffs of pesticides such as neonicotinoids, which are known to alter anuran survival, behaviour, predation stress response, and development. However, few studies have investigated the possible interactions between neonicotinoids and natural environmental stressors which could alter the strength and direction of observed neonicotinoid effects. This study investigated how a concentration of imidacloprid (a neonicotinoid) measured in surface waters interacted with high population density, an important environmental stressor, to influence behaviour and development across metamorphosis in wood frogs (Lithobates sylvaticus) known to breed in agricultural landscapes. I reared tadpoles in a fully crossed design experiment, between two densities (0.33 and 1 tadpole/L) and clean vs contaminated water (10 µg/L imidacloprid). Behaviours were measured in the absence and presence of predation cues using open-field tests at three distinct developmental stages, up to the metamorph stage. I found that imidacloprid did not interact with population density or independently affect behaviours in the absence of predation cues. However, individuals raised at high density compared with low density were more active at an early developmental stage but less active at metamorphic climax. Furthermore, both density and imidacloprid independently decreased the natural behavioural response (i.e., “freezing”) of tadpoles to predation cues. Both treatments also slightly accelerated metamorphosis while only density altered final mass at metamorphosis. Finally, I found that distance travelled was weakly repeatable between aquatic stages but not repeatable across metamorphosis, a pattern that was not affected by treatments. This study provides novel insights on the ecotoxicology of imidacloprid in the presence of a natural stressor, highlighting the importance of including behavioural assays and stressors in studies of amphibian ecotoxicology.
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Grimes, Peter Julian. „It's better than catching frogs : exploring inclusion in relation to local context in Lao PDR and Thailand“. Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/its-better-than-catching-frogsexploring-inclusion-in-relation-to-local-context-and-knowledge-in-lao-pdr-and-thailand(d74d830a-4450-4ce1-a614-806739dd7b64).html.
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This thesis examines the applicability of pre-dominantly Western theories of inclusive school development in countries of the Global South. Firstly, the findings of a review of research literature are used to develop a typology to describe the common features of inclusive schools, incorporating ways in which they might be supported. This typology was then used to explore the ways in which schools in the Lao People's Democratic Republic and Thailand developed inclusive practices. Engagement with school systems in these countries over a period of six years between 2003 and 2009 provided opportunities to work at several different levels with schools that in some way defined themselves as being 'inclusive'. Using data generated through field work with schools in an Inclusive Education Project in Laos and one school in Thailand, tensions were identified between the theoretical framework and my initial research findings. A revision of the typology was undertaken, drawing on a wider literature to take account of additional factors such as local and national culture and the impact of the policy context in these countries. The researcher often had the role of consultant, creating tensions in the way he constructed his position and also in the schools’ response. Reflecting on these tensions became a productive process in terms of understanding the factors which effectively promoted the development of inclusion in these different contexts. In particular, the process highlighted the relatively neglected significance of local context and knowledge and the way in which these factors impact on inclusive school development. In order to explore these issues in greater detail, further research was then undertaken in one school in Laos, creating a case study developed over four years. This detailed engagement revealed more clearly the limits of typologies in general and of Western theories in particular. Whilst they may offer a lens for examining inclusive school development they do not 'adequately' account for variable factors rooted in the local context. In conclusion, policy initiatives designed to support the development of more inclusive schools must allow for the creation of space at local levels for meanings to be constructed which will support teachers in developing their own sense of agency and making changes in their practice of which they have ownership.
11
Wang, Yu. „HPLC method development for the evaluation of pheromones from the dwarf African clawed frog Hymenochirus : a thesis“. Scholarly Commons, 2001. https://scholarlycommons.pacific.edu/uop_etds/587.
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12
Cave, Ashley E. „Grey treefrog tadpole development and behavior altered by dicamba herbicide exposure“. Wittenberg University Honors Theses / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wuhonors1623757491963071.
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13
Gluesenkamp, Andrew Gallagher. „Developmental mode and adult morphology in bufonid frogs : a comparative analysis of correlated traits /“. Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3008336.
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14
Paloski, Rori A. „Relationship between lakeshore development and anuran populations in Portage County, Wisconsin /“. Link to full-text, 2006. http://epapers.uwsp.edu/thesis/2006/paloski.pdf.
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15
Boyd, Jonathan Lomax. „Evolutionary Analysis of the Glutamic Acid Decarboxylase 67 Immediate Upstream Region in African Clawed Frogs“. W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539626884.
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16
Flores, De Gracia Eric Enrique. „Early development and the honesty of aposematic signals in a poison frog“. Thesis, University of Exeter, 2012. http://hdl.handle.net/10871/8170.
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The causes and consequences of variation in aposematic signals during immature stages are not clearly understood. This thesis explores the effects of early environment on the expression of aposematic signals in the green and black poison frog (Dendrobates auratus), and the consequences of variation in such components in the wild. It also explores how aposematic expression relates to levels of chemical defences in immature froglets. Embryos and larvae of poison frogs in the genus Dendrobates are known to be darkly pigmented. This thesis reports for the first time polymorphism in egg pigmentation in D. auratus and ontogenetic colour change through development reverting to a normally pigmented phenotype; however whether this pigmentation results from constraints or has adaptive consequences remains unclear. Evidence on how immature individuals allocate resources to growth and warning signalling is scarce. Experimental results in this thesis show that food supply during early environment affected body size and signal luminance in post-metamorphic froglets. Therefore the relative importance of these traits in relation to predation risk was further tested, using artificial prey in a field experiment. The results indicated that rates of attack by birds correlated negatively with body size, and on the contrary survival of artificial prey was independent of signal luminance. I therefore tested the hypothesis that in the wild larger, relatively well-nourished juvenile frogs are chemically better defended. I found that in fact larger juveniles are at a selective advantage conferred by their greater foraging efficiency and their superior levels of chemical defences. Overall, these results shows plasticity in aposematic traits in relation to early environmental nutrition in D. auratus; and suggests that acquiring large body size and similar integument colour as to adults are key determinants for survival during the early stages of their terrestrial life.
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Kirschman, Lucas James. „The Effects of Neuroendocrine Stress on Larval Development“. OpenSIUC, 2017. https://opensiuc.lib.siu.edu/dissertations/1451.
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Environmental stressors are ubiquitous. Animals will face a variety of natural and anthropogenic stressors throughout their life cycle. The physiological mechanisms that mediate stressful stimuli can have pleiotropic effects on life history traits, such as reproduction and development. Furthermore, these phenotypic changes can affect larger-scale ecosystem dynamics, like nutrient cycling and disease epizootics. Animals are not equally susceptible to stressors across all stages of their life cycles. Critical windows of development, common in young and developing animals, are time periods when stressors have an outsized effect and can permanently alter phenotype. Larval amphibians use a critical window in late larval development wherein activation of the hypothalamic-pituitary-adrenal/interrenal (HPA/I) axis speeds their development, allowing them to metamorphose and escape suboptimal aquatic habitat. Accelerated development comes at a cost, the glucocorticoid (GC) hormones secreted by the HPA/I axis affect other systems such as growth, immune function, metabolism, and nutrient use. In chapter two, I investigated the effects of GC hormones on metabolism, energetics, and nutrient oxidation in larval wood frogs. The results show that GC hormones increase metabolism, reduce lipid stores, and increase protein oxidation during metamorphic climax. Chapter three focuses on the effects of GC hormones on immune function and r susceptibility. I found that chronic exposure to GC hormones increased ranavirus replication in infected wood frog larvae, but did not affect survival time. This could contribute to ranavirus epizootics. Acute GC hormone exposure increased survival, possibly by activing the inflammatory response. Finally, chapter four investigates the effects of GC hormones on nutrient stoichiometry. I found that larvae treated with GC hormones had lower nitrogen to phosphorus ratios, possibly because disrupted skeletal ossification. They also had reduced phosphorus excretion, which could affect ecosystem-level processes like nutrient cycling and decomposition.
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Quadroni, Manfredon. „Characterisation of phosphorylared froms of calmodulin and the development of new techniques for analysing cell proteins /“. Zürich, 1995. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=11321.
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19
Currie, Stephen Paul. „The development and neuromodulation of motor control systems in pro-metamorphic Xenopus laevis frog tadpoles“. Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/10199.
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My thesis has accomplished 3 significant contributions to neuroscience. Firstly, I have discovered a novel example of vertebrate deep-brain photoreception. Spontaneously generated fictive locomotion from the isolated nervous system of pro-metamorphic Xenopus tadpoles is sensitive to the ambient light conditions, despite input from the classical photoreceptive tissues of the retina and pineal complex being absent. The photosensitivity is found to be tuned to short wavelength UV light and is localised to a small region of the caudal diencephalon. Within this region, I have discovered a population of neurons immuno-positive for a UV-specific opsin protein, suggesting they are the means of phototransduction. This may be a hitherto overlooked mechanism linking environmental luminance to motor behaviour. Secondly, I have advanced the collective knowledge of how both nitric oxide and dopamine contribute to neuromodulation within motor control systems. Nitric oxide is shown to have an excitatory effect on the occurrence of spontaneous locomotor activity, representing a switch in its role from earlier in Xenopus development. Moreover, this excitatory effect is found to be mediated in the brainstem despite nitric oxide being shown to depolarise spinal neurons. Thirdly, I have developed a new preparation for patch-clamp recording in pro-metamorphic Xenopus tadpoles. My data suggest there are several changes to the cellular properties of neurons in the older animals compared with the embryonic tadpole; there appears to be an addition of Ih and K[sub](Ca) channels and the presence of tonically active and intrinsically rhythmogenic neurons. In addition, I have shown that at low doses dopamine acts via D2-like to hyperpolarise the membrane potential of spinal neurons, while at higher doses dopamine depolarises spinal neurons. These initial data corroborate previously reported evidence that dopamine has opposing effects on motor output via differential activation of dopamine receptor subtypes in Xenopus tadpoles.
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Bharathan, Navaneetha Krishnan. „USING THE FROG EPIDERMIS TO UNCOVER DESMOSOME FUNCTION AND REGULATION IN THE DEVELOPING EMBRYO“. VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5313.
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The desmosome is one of the major cell adhesion junctions found in the epithelia, heart, and hair follicle. Described as a “rivet” that hold cells together, it provides these tissues with the integrity to withstand the tremendous forces they face in everyday life. Defects in this junction can lead to devastating diseases where patients are susceptible to skin infections and cardiovascular defects. Limited treatments exist for diseases of the desmosome, and strategies do not target all symptoms. Therefore, delineating the function and regulation of desmosomes is of paramount importance for the development of prevention and treatment strategies. The Xenopus laevis has been utilized for the study of embryonic development and tissue movements. This study takes advantage of the frog model to study a key desmosomal protein, desmoplakin (Dsp), in the epidermal development of the embryo. First, Xenopus embryonic epidermis has junctional desmosomes as early as the blastula stages. Desmosomes numbers per junction increase as the embryo develops. Dsp is present in many epidermally-derived structures in the embryo at varying levels. Xenopus embryos deficient in desmoplakin have phenotypic defects in epidermal structures and the heart, mimicking mammalian models. Embryos with reduced Dsp exhibit an increased susceptibility to epidermal damage under applied mechanical forces. Assays also reveal a potential role for desmosomes in radial intercalation, a process through which cells move from the inner to the outer epidermal layers. Embryos with reduced Dsp exhibit a slight reduction in intercalation and defects in intercalating cell types, including multiciliated cells and small secretory cells. Finally, c-Jun N-terminal kinase (JNK) may have a potential role in the regulation of desmosome assembly and adhesion. Embryos with deficient Dsp display a partial recovery of mechanical integrity when treated with a JNK inhibitor.
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Borges, Figueiredo Ana Leonor. „Control of cell specification and migration during early frog development by PFKFB4, a key glycolysis regulator“. Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112107.
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L’ectoderme embryonnaire devient spécifié en ectoderme non-neural, plaque neurale et bordure neurale à la fin de la gastrulation. Les cellules de bordure neurale sont les progéniteurs de la crête neurale et des placodes. La crête neurale est une population transitoire de cellules multipotentes, qui se forme au cours de la neurulation. Quand les bourrelets neuraux s’élèvent pour former le tube neural, les cellules de la crête neurale subissent une transition épithélio-mésenchymateuse, migrent dans l'ensemble du corps pour atteindre leur destination finale et se différencier. La crête neurale donne naissance à de multiples dérivés tels que les neurones et les cellules gliales du système nerveux périphérique, le cartilage et les os du visage, ou encore les mélanocytes. Des régulations complexes, impliquant de nombreuses signalisations et la transcription de gènes-clé, orchestrent ces événements. Cependant, les premières étapes menant à la formation de la crête neurale et à la spécification précoce de la bordure neurale sont encore peu comprises. Nous avons analysé le transcriptome de la crête neurale d'embryon de l'amphibien Xenopus laevis, à la recherche de nouveaux régulateurs des premières étapes de la formation de la crête neurale. Nous avons constaté que le régulateur de la glycolyse PFKFB4, est exprimé dans l’ectoderme dorsal de la jeune gastrula et dans les cellules de la crête neurale. Ici, nous démontrons que PFKFB4 régule la spécification de l’ectoderme via la voie de signalisation Akt, indépendamment de la glycolyse, démontrant ainsi la première fonction non-glycolytique des enzymes PFKFB. En outre, cette régulation est essentielle pour permettre aux progéniteurs de l'ectoderme d’être spécifiés en plaque neurale, crête neurale, placodes ou ectoderme non neural, mettant en évidence un nouveau point de contrôle de développement. De plus, nous démontrons que PFKFB4 régule des étapes ultérieures de la formation de la crête neurale. Notre travail met en évidence que les régulateurs du métabolisme cellulaire possèdent des fonctions non-métaboliques pour contrôler des étapes de développement au cours du développement embryonnaireEmbryonic ectoderm becomes specified into non-neural ectoderm, neural plate and neural border at the end of gastrulation. Neural border cells are the progenitors of the neural crest and placodes. The neural crest is a transient population of multipotent cells, which forms during neurulation. As the neural border elevates to form the neural tube, neural crest cells undergo an epithelial to mesenchymal transition, migrate extensively into the whole body to reach their final destinations and differentiate. Neural crest gives rise to multiple derivatives such as neurons and glia, facial cartilage, bones, melanocytes and sympatho-adrenal cells. A complex interplay of signaling and transcriptional regulations orchestrates these early patterning events. However, the first steps leading to NC formation and early specification at the NB are less understood. We analysed the NC transcriptome of frog embryos, to look for novel regulators of the early steps of NC formation. We found that the well-known glycolysis regulator PFKFB4, is expressed in early gastrula dorsal ectoderm, and in neurula neural crest cells. Here, we demonstrate that PFKFB4 regulates ectoderm specification via Akt signaling independently of glycolysis, thus demonstrating the first non-glycolytic function of PFKFB enzymes. Moreover, this regulation is essential to allow ectoderm embryonic progenitors to be patterned into neural plate, neural crest, placodes and definitive ectoderm, highlighting a novel developmental checkpoint. Moreover, we also demonstrate that PFKFB4 regulates later steps of neural crest formation. Our work highlights that regulators of cell metabolism accumulate non-metabolic related functions to control developmental steps during embryonic development
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Gutierrez, Villagomez Juan Manuel. „Effects of Naphthenic Acids and Acid Extractable Organic Mixtures on Development of The Frog Silurana (Xenopus) Tropicalis“. Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37707.
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Naphthenic acids (NAs) are oil-derived mixtures of carboxylic acids and are aquatic contaminants of emerging concern. The objective of the research presented in this thesis was to investigate the toxicity of NAs in tadpoles of the frog Silurana (Xenopus) tropicalis. Using electrospray ionization high-resolution mass spectrometry (ESI-HRMS), I determined that the proportions of O2 (presumably carboxylic acid moiety) species were 98.8, 98.9 and 58.6% respectively, for two commercial extracts (S1 and S2), and acid extractable organics (AEOs) from oil sands process-affected water (OSPW). The rank order potency based on the lethal concentration fifty (LC50) and effect concentration fifty (EC50) with and without normalization for the quantity of O2 species was S1 > S2 > AEO. The main effects observed were reduced body size, edema, and cranial, cardiac, gut and ocular abnormalities. Oligonucleotide microarray technology was used to determine the transcriptomic responses in developing S. tropicalis embryos following exposure to S1 and S2 at a sub-lethal concentration of 2 mg/L. Some of the significantly enriched pathways (p < 0.05) included metabolism and cell membrane depolarization, and some were related to observed abnormalities including edema, gastrointestinal system, and cartilage differentiation. I established and validated a derivatization method for NAs using pentafluorobenzyl bromide (PFBBr) prior to gas chromatography-electron impact mass spectrometry (GC-EIMS) to increase chromatographic resolution, and sensitivity, compared to boron trifluoride-methanol (BF3/MeOH) and N-tert-Butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA). Solid-phase microextraction of volatiles originating from S1, S2, Merichem NAs and an AEO mixture led to the identification of 54, 56, 40 and 4 compounds, respectively. The compounds identified in the mixtures included aliphatic and cyclic hydrocarbons, carboxylic acids, alkyl-benzenes, phenols, naphthalene and alkyl-naphthalene, and decalin compounds. To determine the chemical nature of the toxic compounds in NA mixtures, the S2 and AEOs preparations were fractionated using open column chromatography. A non-polar and a polar fraction were obtained from S2. Overall, the toxicity of the polar fraction was not significantly different from whole S2 (p > 0.05). Six fractions of AEOs were obtained, however because of limited material, only the toxicities of F3 and F4 were assessed. The toxicity of F3 was significantly lower than AEOs (p < 0.05) and F4 was not toxic for S. tropicalis (p > 0.05). These results suggest that during fractionation, toxic compounds were lost or that the toxicity of AEOs results from the combined effects of the compounds present in the whole extract. The toxicological dose descriptors, morphometric, transcriptomic and chemical analysis herein presented may contribute to the development of environmental guidelines for NAs and AEOs.
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Sharp, Colleen C. R. „Effects of copper and light exposure on the development and survival of the Wood Frog tadpole (Rana sylvatica)“. University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1209657636.
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Blech-Hermoni, Yotam. „Roles of CUG-BP, Elav-Like Family Member 1 (CELF1), an RNA Binding Protein, During Vertebrate Heart Development“. Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1417636826.
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Pan, Tien-Chien. „Metabolic, cardiac and ventilatory regulation in early larvae of the South African clawed frog, Xenopus laevis“. Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc12175/.
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Early development of O2 chemoreception and hypoxic responses under normoxic (150 mmHg) and chronically hypoxic (110 mmHg) conditions were investigated in Xenopus laevis from hatching to 3 weeks post fertilization. Development, growth, O2 consumption, ventilatory and cardiac performance, and branchial neuroepithelial cells (NEC) density and size were determined. At 3 days post fertilization (dpf), larvae started gill ventilation at a rate of 28 ± 4 beats/min and showed increased frequency to 60 ± 2 beats/min at a PO2 of 30 mmHg. Also at 3 dpf, NECs were identified in the gill filament buds using immunohistochemical methods. Lung ventilation began at 5 dpf and exhibited a 3-fold increase in frequency from normoxia to a PO2 of 30 mmHg. Hypoxic tachycardia developed at 5 dpf, causing an increase of 20 beats/min in heart rate, which led to a 2-fold increase in mass-specific cardiac output at a PO2 of 70 mmHg. At 10 dpf, gill ventilatory sensitivity to hypoxia increased, which was associated with the increase in NEC density, from 15 ± 1 to 29 ± 2 cells/mm of filament at 5 and 10 dpf, respectively. Unlike the elevated rate, cardiac and ventilatory volumes were independent of acute hypoxia. Despite increased cardioventilatory frequency, larvae experienced an average of 80% depression in during acute hypoxia. Chronic hypoxia (PO2 of 110 mmHg) decreased mass-specific cardiac performance before 10 dpf. In older larvae (10 to 21 dpf), chronic hypoxia decreased acute branchial and pulmonary hypoxic hyperventilation and increased NEC size. Collectively, these data suggest that larvae exhibit strong O2-driven acute hypoxic responses post-hatching, yet are still O2 conformers. All acute hypoxic responses developed before 5 dpf, and then the effects of chronic hypoxia started to show between 7 and 21 dpf. Thus, the early formation of acute hypoxic responses is susceptible to the environment and can be shaped by the ambient PO2.
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Singhal, Nishant. „The role of Xenopus BRG1, a conserved subunit of SWI/SNF class of remodeling complexes, during early frog development“. Diss., lmu, 2005. http://nbn-resolving.de/urn:nbn:de:bvb:19-41841.
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Pollard, Stephen J. „Development and verification of an aerodynamic model for the NPS FROG UAV using the CMARC panel code software suite“. Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA354951.
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Thesis (Degree of Aeronautical and Astronautical Engineer) Naval Postgraduate School, September 1998."September 1998." Thesis advisor(s): Max F. Platzer, Kevin D. Jones. Includes bibliographical references (p. 181-182). Also available online.
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Arauco, Luis Ricardo Romero [UNESP]. „Efeito do extrato hidroalcoólico de própolis em girinos de rã touro (Rana Catesbeiana)“. Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/100223.
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Universidade Estadual Paulista (UNESP)
Foi avaliado o efeito do extrato hidroalcoólico de própolis (0,0; 0,2; 0,5; 1,0; e 1,5 %) misturado em ração comercial (45 % Proteína Bruta), em girinos de rã-touro. Foram utilizados 1400 girinos no estágio 26 da tabela de Gosner (1960), distribuídos em 20 tanques experimentais com 70 litros de água, na densidade de um girino por litro. O arraçoamento foi realizado quatro vezes ao dia. Para análise dos dados do ganho de peso, comprimento, sobrevivência, conversão alimentar, consumo de ração e metamorfose, foi utilizado um delineamento inteiramente casualizado com cinco tratamentos e quatro repetições. No final do experimento, foi colhido sangue do vaso caudal, de cinco girinos de cada repetição. A contagem diferencial de leucócitos foi realizada em extensões coradas pelo método de Rosenfeld (1947), em microscopia de luz. Foram contadas 100 células por lâmina. Para avaliar o efeito do extrato hidroalcoólico de própolis na porcentagem de leucócitos, usou-se um delineamento inteiramente casualizado com cinco tratamentos e três repetições. Para análise histológica no final do experimento foram sacrificados três girinos de cada repetição e retirada amostras do rim, fígado e intestino para lâminas histológicas. As amostras foram fixadas em formol, desidratadas em uma série de álcool, coradas com HE, analisadas e fotomicrografadas com fotomicroscópio Axiophot- Zeiss em microscópio óptico e medido com micrometro ocular a espessura do epitélio intestinal. Para análise estatística dos dados foi usado um delineamento inteiramente casualizado com cinco tratamentos e três repetições. A sobrevivência, consumo de ração, conversão alimentar e comprimento dos girinos, não foram influenciados pelo extrato hidroalcoólico de própolis. O ganho de peso foi influenciado significativamente (P < 0,05) observando-se...
The effect of the propolis hidroalcoolic extract was evaluated (0.0; 0.2; 0.5; 1.0; and 1.5 %) mixed to the commercial ration (45 % CP) in bullfrog tadpoles. 1,400 tadpoles were used at stage 26 (Gosner ,1960), distributed in twenty experimental tanks with 70 liters of water, in the density of one tadpole per liter. The feding was four times a day. For analysis of the data of the weight gain, length, survival, feed conversion, ration consumption and metamorphosis were used a completely randomized design with five treatments and four repetitions. In the end of the experiment, it was picked the blood of the vase flow, of five tadpoles of each repetition. The differential counting of leuccytes was accomplished in red-faced extensions by the method of Rosenfeld (1947), in light microscopia. To evaluate the effect of the propolis hidroalcoolic extract in the percentage of leucocytes, were used a completely randomized design with five treatments and three repetitions. They were counted 100 cells for sheet. For histological analysis in the end of the experiment three tadpoles of each repetition were sacrificed and samples of the kidney, liver and intestine were removed for you laminate histological. The samples were fastened in formol, dehydrated in one serializes of alcohol, red-faced with HE analyzed and fotomicrographed with fotomicroscópio Axioskop-Zeiss in optical and measured microscope with ocular micrometer the espessor of the intestinal epithelium. For statistical analysis of the data were used a completely randomized design with five treatments and three repetitions. The survival, ration consumption, feed conversion and length of the tadpoles, were not influenced by the propolis hidroalcoolic extract. The weight gain was influenced significantly (P< 0,05) being observed a worse in the tadpoles... (Complete abstract click electronic access below)
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King, Kimberly L. P. „Effects of exposure to Eurasian Milfoil (Myriophyllum spicatum) on the growth and development of Xenopus laevis and the Columbia spotted frog (Rana Lutriventris)“. Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/K_King_112607.pdf.
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Ott, Tim [Verfasser], und Martin [Akademischer Betreuer] Blum. „Studies of human genetic diseases and developmental processes with the frog Xenopus laevis / Tim Ott ; Betreuer: Martin Blum“. Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2021. http://d-nb.info/1232545139/34.
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Michel, Laura. „On the function of Xenopus Oct4 protein homologs: Molecular construction of dominant interference variants and functional analysis in early frog development“. Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-136130.
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King, Marie Kumsher. „Evaluation of the Developmental Effects and Bioaccumulation Potential of Triclosan and Triclocarban Using the South African Clawed Frog, Xenopus Laevis“. Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc33178/.
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Triclosan (TCS) and triclocarban (TCC) are antimicrobials found in U.S. surface waters. This dissertation assessed the effects of TCS and TCC on early development and investigated their potential to bioaccumulate using Xenopus laevis as a model. The effects of TCS on metamorphosis were also investigated. For 0-week tadpoles, LC50 values for TCS and TCC were 0.87 mg/L and 4.22 mg/L, respectively, and both compounds caused a significant stunting of growth. For 4-week tadpoles, the LC50 values for TCS and TCC were 0.22 mg/L and 0.066 mg/L; and for 8-week tadpoles, the LC50 values were 0.46 mg/L and 0.13 mg/L. Both compounds accumulated in Xenopus. For TCS, wet weight bioaccumulation factors (BAFs) for 0-, 4- and 8-week old tadpoles were 23.6x, 1350x and 143x, respectively. Lipid weight BAFs were 83.5x, 19792x and 8548x. For TCC, wet weight BAFs for 0-, 4- and 8-week old tadpoles were 23.4x, 1156x and 1310x. Lipid weight BAFs were 101x, 8639x and 20942x. For the time-to-metamorphosis study, TCS showed an increase in weight and snout-vent length in all treatments. Exposed tadpoles metamorphosed approximately 10 days sooner than control tadpoles. For the hind limb study, although there was no difference in weight, snout-vent length, or hind limb length, the highest treatment was more developed compared to the control. There were no differences in tail resorption rates between the treatments and controls. At relevant concentrations, neither TCS nor TCC were lethal to Xenopus prior to metamorphosis. Exposure to relatively high doses of both compounds resulted in stunted growth, which would most likely not be evident at lower concentrations. TCS and TCC accumulated in Xenopus, indicating that the compound has the potential to bioaccumulate through trophic levels. Although TCS may increase the rate of metamorphosis in terms of developmental stage, it did not disrupt thyroid function and metamorphosis in regards to limb development and tail resorption.
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Crump, Douglas. „The effects of the xenoestrogen, octylphenol (OP), and UV-B radiation on somatic development and hypothalamic gene expression of the leopard frog (Rana pipiens)“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0015/MQ57102.pdf.
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Michel, Laura L. [Verfasser], und Ralph [Akademischer Betreuer] Rupp. „On the function of Xenopus Oct4 protein homologs : molecular construction of dominant interference variants and functional analysis in early frog development / Laura Michel. Betreuer: Ralph Rupp“. München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/101723311X/34.
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Long, Hannah Katherine. „Evolutionary usage and developmental roles of vertebrate non-methylated DNA“. Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:78b14c1d-1fa3-46f1-815f-a8ba55579c43.
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Vertebrate genomes exhibit global methylation of cytosine residues where they occur in a cytosine-guanine dinucleotide (CpG) context and this epigenetic mark is generally thought to be repressive to transcription. Punctuating this pervasive DNA methylation landscape are short, contiguous regions of non-methylated DNA which are found at two thirds of mammalian gene promoters. These non-methylated regions exhibit CpG content close to expected levels as they escape the depletion of CpGs observed across the methylated fraction of the genome. The unique nucleotide properties of these CpG island (CGI) regions enable their identification by computational prediction in mammalian genomes. Owing to a lack of high-resolution genome-wide DNA methylation profiles in non-mammalian species, these CGI predictions have often been used as a proxy for non-methylated DNA in these organisms. In contrast to mammals, CGI predictions in cold-blooded vertebrates rarely coincide with gene promoters, leading to the belief that CGls are significantly divergent between vertebrate species, and that unique promoter-associated features may have been acquired during warmblooded vertebrate evolution. This thesis is primarily concerned with the location, establishment and biological function of non-methylated islands of DNA in vertebrate genomes. To experimentally determine genome-wide profiles of non-methylated DNA, a novel biochemical technique was established called biotinylated ZF-CxxC affinity purification (Bio-CAP), and development of this method is discussed in Chapter 3. Experimental analysis of non-methylated DNA profiles in this thesis initially addresses two main questions: (1) 'How does the non-methylated DNA landscape compare genome-wide for seven vertebrates considering distinct tissue types and developmental stages?' (2) 'How are vertebrate non-methylated regions of DNA defined and interpreted in the nuclear environment?' To address the first question, non-methylated DNA was profiled by Bio-CAP sequencing across the genomes of seven diverse vertebrate species, representing all major branch points of vertebrate evolution, and the results are discussed in Chapters 4 and S. Contrary to previously held dogma, experimentally determined nonmethylated islands of DNA (NMls) constitute an ancient epigenetic feature of vertebrate gene regulatory elements. However, despite having numerous high-resolution maps of vertebrate non-methylated DNA, the means by which NMls are identified and maintained in the nuclear environment remains poorly understood. To address the second question and identify features which determine the methylation state of DNA, exogenous DNA sequences were introduced into mouse embryonic stem (ES) c~.II~. Non-methylated DNA was profiled by Bio-CAP sequencing to investigate how different features, such as sequence-specific binding motifs, chromatin architecture and nucleotide composition of a given DNA sequence impact local DNA methylation patterns. Interestingly, the majority of exogenous promoters were appropriately non-methylated in mouse ES cells, germline and somatic cells suggesting that gene promoters have retained strong signals for the nonmethylated state across millions of years of evolution (discussed in Chapter 6). During mouse embryogenesis, genome-scale DNA demethylation and remethylation events occur to remodel the epigenetic landscape and loss of DNA methylation during this time leads to embryonic lethality. To investigate the biological function of non-methylated DNA, the third question addressed in this thesis is (3) 'What is the developmental importance of non-methylated islands of DNA during vertebrate embryogenesis?' To investigate this, members of the ZF-CxxC domain-containing family of chromatin modifiers were ablated in zebrafish embryos to perturb the chromatin landscape at NMls, and therefore interfere with their function during early development (Chapter 7). Early embryonic development and patterning was disrupted in knockdown embryos, suggesting that interpretation of non-methylated DNA and placement of chromatin modifications at NMls is essential for normal zebrafish embryogenesis. Together this work sheds light on the evolutionary origins of NMls, the mechanisms involved in the recognition and establishment of nonmethylated loci and provides an insight into the function of non-methylated DNA during early embryonic development.
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Tyler, Michael J. 1937. „The biology and systematics of frogs : contributions submitted to The University of Adelaide / by Michael J. Tyler“. 2002. http://hdl.handle.net/2440/38581.
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Vol. [2] comprises 6 reprints of published monographs in box folder; but numbered within the publications submitted listing (90 items), and within the 3 categories identified; at the beginning of vol. 1.Includes bibliographical references.
2 v. (various pagings) :
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Comprises 90 contributions to the biology and systematics of frogs, with particular emphasis upon those concerning the fauna of Australia and New Guinea. Provides an understanding of the state of knowledge when the author commenced his studies; permitting the extent of his work, an the nature of its significance, to be evaluated.
Thesis (D.Sc.)--University of Adelaide, Dept. of Environmental Biology, 2002
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Baugh, Alexander Taylor. „The development and execution of mate choice in túngara frogs“. 2009. http://hdl.handle.net/2152/8457.
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Interest in the question of when and how species recognition and mate preferences emerge in animals with strong species-typical predispositions has faded since the time of the classical ethologists. In its place, the role of plasticity has surfaced as a central emphasis in the study of animal behavior. Here, I step back and examine the origin and execution of sexual behavior in a tropical frog for which auditory predispositions are key. These experiments challenge assumptions about behavioral development, auditory perception, and stereotyped behavior. First, I illustrate when and how a sex- and species-typical behavior—conspecific phonotaxis—emerges during development. This study demonstrates that phonotaxis, presumably restricted to mature females, is present in both sexes early in postmetamorphic development—potentially long before such behavior might serve an adaptive function. I place this result in the context of hypotheses regarding the development of learned versus non-learned behaviors, and in light of the potential for perception to be altered by physiological changes occurring concomitantly with ontogeny. Next, I describe a set of dynamic mate choice studies that highlight how decision-making in a relatively simple system is more flexible, and less stereotyped, than was previously assumed. Results here show that frogs temporally update their mate choice decisions in a moment-to-moment fashion as advertisement signals change in real time. By decomposing the decision-making process, I determine the stimulus parameters essential for commitment to an initial phonotactic approach. These studies are followed up by experiments that reveal a high level of individual variation in female choosiness during mate choice. Lastly, I describe a mate choice study that revealed categorical perception in frogs, the first “lower” vertebrate now known to exhibit a perceptual mode previously considered a hallmark of “higher” organisms. Collectively, I make the following arguments: (1) constraints on sensory systems play a larger role in shaping behavior than is generally appreciated, irrespective of the involvement of learning; (2) unstudied sources of variation may contribute significantly to the raw material for sexual selection; and (3) phonotaxis in anurans amphibians is not the simple, stereotyped behavior that has been suggested of it in the past.text
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Park, Bradley J. „Effects of the environmental estrogen 17α-ethynylestradiol on early development of green frogs (Rana clamitans) and mink frogs (R. septentrionalis) at the Experimental Lakes Area (Ontario, Canada)“. 2003. http://hdl.handle.net/1993/19987.
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Park, Bradley J. „Effects of the environmental estrogen 17[alpha]-ethynylestradiol on early development of green frogs (Rana clamitans) and mink frogs (R. septentrionalis) at the Experimental Lakes Area (Ontario, Canada)“. 2003. http://hdl.handle.net/1993/19987.
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Chen, Jianye. „Evolution and biogeography of frogs and salamanders, inferred from fossils, morphology and molecules“. Thesis, 2016. https://doi.org/10.7916/D8GX4BSN.
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Classified in the Lissamphibia, modern amphibians are the only non-amniote tetrapods living today. They consist of three morphologically distinct groups: the tailless frogs and toads (Anura), the limbless caecilians (Gymnophiona), and the tailed salamanders and newts (Urodela). With 205 species, the caecilians are highly specialized worm-like forms that live a fossorial lifestyle, with a relatively narrow distribution in the tropic rainforests of South America, Africa and Asia (Duellman and Trueb, 1994; Amphibiaweb, 2015). Salamanders, with 683 species, are widely distributed in the North America, Asia and Europe, with a few plethodontids extending to Central and South America (Duellman and Trueb, 1994; Amphibiaweb, 2015). Frogs are the most diverse amphibian groups, with 6644 species distributed over all continents except Antarctica (Duellman and Trueb, 1994; Amphibiaweb, 2015). Both frogs and salamanders develop a wide array of lifestyles, ranging from terrestrial, aquatic, fossorial to aboreal lifestyles (Duellman and Trueb, 1994). During ontogeny, amphibian larvae usually undergo a drastic post-embryonic shift into an adult form, a term known as metamorphosis. In salamanders, another developmental pathway – neoteny – also occurs, in which the larval morphology is retained in sexually mature adults (Duellman and Trueb, 1994; Rose, 2003). Because of the diverse lifestyles and developmental pathways, frogs and salamanders are often used as model systems in many fields of biology (e.g., evo-devo).
Over a century, but especially in the past two decades, a wealth of frog and salamander fossils has been discovered from the Mesozoic and Cenozoic of East Asia (e.g., Noble, 1924; Young, 1936; Borsuk-Bialynicka, 1978; Gao, 1986; Dong and Wang, 1998; Gao and Shubin, 2001, 2003, 2012; Gao and Wang, 2001; Gao and Chen, 2004; Wang and Rose, 2005; Wang and Evans, 2006b; Zhang et al., 2009; Chen et al., 2016; this study). Some of these fossils represent the earliest members of many crown clades, including the earliest crown salamanders from the Middle Jurassic (~165 Ma, Gao and Shubin, 2003), the earliest salamandroid from the Late Jurassic, the earliest sirenid from the Late Jurassic (this study), and the earliest spadefoot toads from the late Paleocence (Chen et al., 2016). Other fossils also bear important anatomical, temporal and geographical information in understanding their evolution. Unfortunately, the importance of many of these fossils remains obscure in a phylogenetic context. For example, an early-middle Oligocene Mongolian spadefoot toad Macropelobates osborni (Noble, 1924) was discovered outside the current distribution of spadefoot toads, yet its phylogenetic position and its implication on spadefoot toad biogeography remain not well understood.
A major reason for the poor understanding of these fossils can be attributed to a trend of dichotomy between morphological and molecular phylogenies on amphibians. Whereas morphologists and paleontologists sometimes use a relatively small morphological dataset to reconstruct relationships (e.g., Gao and Shubin, 2012; Henrici, 2013), large-scale phylogenies are almost always conducted with molecular data with only living taxa (e.g., Roelants and Bossuyt, 2005; Pyron and Wiens, 2011). Very few studies on amphibian phylogeny have combined morphological and molecular data together, and even fewer also combined fossils. Because of this, the positions of many important fossils remains unclear, and the evolutionary scenarios inferred from only living species can sometimes be inconsistent with fossil evidence.
In this thesis, I adopt a total-evidence approach to understand the evolution of amphibians, especially frogs and salamanders. I will incorporate information from fossils, morphology and molecules together to reconstruct the relationships. Compared with studies with each individual datasets, this approach incorporates all available data in a single analysis, with a goal to reach robust and congruent results that allow further discussions on character evolution and biogeographic reconstruction. The inclusion of fossils directly into the combined analysis provides the time dimension that is independent from molecular data (Norell, 1992). The anatomical combination of fossils can represent intermediate forms that help to solve the “long branch” problems caused by highly specialized modern taxa. The morphological dataset, despite its much smaller size with molecular data, is the only link between fossils and modern taxa. The inclusion of key morphological characters in both reconstructing phylogenetic hypotheses and examining character evolution provide consistent results that allow discussion on the homology/homoplasy of a certain character without ambiguity. The molecular sequence data provides overwhelmingly large data on modern taxa for phylogenetic reconstructions compared with morphological data, which helps to reach a robust hypothesis. Although fossils contain no molecular data, the inclusion of molecular sequence data into the combined analysis does have an effect on the positions of fossil taxa. By altering the relationship “framework” of modern taxa, the character optimization of fossils and other taxa of a combined analysis also varies compared with results of morphology-only analysis, thus changing the positions of fossils. In the following five chapters, I will describe a number of fossil amphibian species, reconstruct three combined phylogenies, and use the results for discussions on character evolution and biogeography.
In Chapter 1 and Chapter 2, I focus on a frog clade called spadefoot toads (Anura: Pelobatoidea). In Chapter 1, I provide descriptions on three important fossil spadefoot toads from the Cenozoic of East Asia and North America: Macropelobates osborni from the early-middle Oligocene of Mongolia, Prospea holoserisca from the latest Paleocene of Mongolia, and Scaphiopus skinneri from the middle Oligocene of the United States. In Chapter 2, I conduct a combined phylogenetic analysis of archaeobatrachian frogs, and discuss the evolution of the bony spade and the historical biogeography of spadefoot toads based on the results of the phylogeny.
In Chapter 3, I describe a new fossil frog from the Early Cretaceous of Inner Mongolia, China. The unique morphology of the new fossil is distinct from previous Early Cretaceous frogs from the Jehol Biota of China. Results of the combined analysis show that the new frog represents a basal member of the Pipanura. Comparisons between the Early Cretaceous frogs from China, Spain and Brazil show a high diversity of species coupled with a high degree of endemism during the Early Cretaceous. I discuss in the phylogenetic context how early frogs gradually reach their postcranial body plan with a shortened vertebral column, loss of ribs, and specialized pelvic regions.
In Chapter 4, I provide a brief review of Mesozoic fossil salamanders from northern China, and describe a new fossil from the Late Jurassic of Liaoning Province, China. I conduct a combined phylogeny of higher-level relationships of salamanders. The new fossil, despite its general-looking appearance, represents a basal member of the highly specialized eel-like neotenic family Sirenidae on the cladogram. I discuss character evolutions in the Sirenidae, and how the neotenic developmental pathway evolved in early salamanders.
In Chapter 5, I conduct a combined phylogenetic analysis of the salamander suborder Cryptobranchoidea, consisting of the neotenic giant salamanders (Cryptobranchidae) and the metamorphic Asiatic salamanders (Hynobiidae). The new morphological matrix includes new characters that were previously less sampled in the hynobranchial region. The monophyly of the Hynobiidae are confirmed by the new analysis, and four unequivocal synapomorphies are found for the clade. An S-DIVA biogeographic reconstruction is conducted to disscuss the distributional patterns of the Hynobiidae.
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„SUB-LETHAL EFFECTS OF ROUNDUP ON TADPOLE DEVELOPMENT AND PREDATOR AVOIDANCE“. Thesis, 2014. http://hdl.handle.net/10388/ETD-2014-01-1406.
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Roundup is a commonly used pesticide applied to agriculture and forest habitats. In Canada and parts of the North Eastern United States, these areas are generally optimal for amphibians due to the presence of small, ephemeral water bodies. While Roundup has been shown to have no adverse effects on a number of species, amphibians are one of the few groups who show high sensitivity to Roundup. My research aims to determine how an acute sub-lethal dose of Roundup affects several different facets of larvae development in wood frogs (Lithobates sylvaticus). In Chapter 2 I examined the effect of Roundup on amphibian development. Groups of tadpoles were treated with Roundup (0.5 mg a.e./L) for four days at three different times in their development (Gosner stage 26, 31-32 and 37-38), while a control group was maintained in similar conditions without Roundup. Pictures were taken every four days until tadpoles reached metamorphosis. Changes in development, body area or length were assessed, along with metamorphic endpoints, such as timing of metamorphosis and weight. Although there was no differential effect of Roundup on tadpole growth or weight, there was a slight, non-ecologically relevant, delay in development in tadpoles treated with Roundup at stage 26. The delay was not detectable in the second half of the experiment, indicating that compensatory mechanisms allowed those individuals to recover. Neither time to metamorphosis or weight at metamorphosis were affected by an environmentally relevant exposure to Roundup. In Chapter 3 I focused on the effect of Roundup on crucial behaviours related to the ability of larval amphibians to detect and avoid predation threats. I demonstrated that being exposed to Roundup for one hour eliminated the response of larval wood frogs to cues from injured conspecifics (i.e. cues known to elicit dramatic anti-predator responses in a wide variety of aquatic species). Tadpoles that were maintained in clean water and exposed to a combination of injured conspecific cues and Roundup, did not exhibit a decrease in movement, when compared to control tadpoles. This result indicates that Roundup deactivates the alarm function of the injured conspecific cues. However, it is possible that both the cues and the animal would be affected by Roundup. In Chapter 3 I also demonstrated that tadpoles that were exposed to Roundup as embryos had reduced basal movement rates. The results of this thesis illustrate that an environmentally relevant concentration of Roundup (0.5 mg a.e./L), does not negatively affect the development of tadpoles. The studies outlined in this thesis suggest that at this exposure concentration, behaviour acts as a more sensitive endpoint, than more traditional morphologic endpoints.
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Whiting, Arthur V. „Factors affecting larval growth and development of the boreal chorus frog Pseudacris maculata“. Phd thesis, 2010. http://hdl.handle.net/10048/1481.
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The boreal chorus frog (Pseudacris maculata) is a widespread species but we know little of its ecology. I examined the nature and existence of competitive mechanisms operating between larvae of the boreal chorus frog and wood frog (Lithobates sylvaticus) from field, mesocosm and laboratory venues spanning nutrient concentrations. I assessed larval performance and diet of tadpoles at natural ponds by measuring tadpole growth and size at metamorphosis, and stable isotope ratios for carbon and nitrogen in tadpole tissue to examine if patterns were consistent with the operation of interspecific competition. In mesocosms I measured chorus frog performance in relation to wood frog presence and nutrient enrichment to confirm the occurrence of competition and examine whether nutrient conditions typical of agriculture ponds impact tadpole performance. In the field I compared larval performance and relative abundance between agricultural ponds and those in Elk Island National Park, to examine whether habitat features surrounding ponds in farmlands reduces the abundance of tadpoles and whether tadpole performance results in reduced abundances. Lastly, I examined whether chemical interference by wood frogs occurs by raising chorus frog tadpoles with caged wood frog tadpoles and/or their feces in the laboratory.
Chorus frog performance was reduced by presence and abundance of wood frog tadpoles. Resource partitioning in natural ponds and overlap in mesocosms, based on stable isotopic analysis, suggest that resource competition occurs. In mesocosms chorus frog performance was reduced by wood frog tadpoles in fertilized treatments and nutrient conditions at agricultural sites are not in themselves detrimental to these anurans. Performance of chorus frog tadpoles in agricultural ponds was unaffected, whereas wood frogs were larger at metamorphosis in crop ponds. Reduced tadpole abundances of both species at these ponds may be related to habitat features or conditions in croplands. The existence of chemical interference in the absence of physical interaction was confirmed, as chorus frogs exposed to wood frog tadpoles and/or feces had reduced growth and were smaller at metamorphosis which could reduce terrestrial survival and future reproduction. My research contributes to our knowledge on boreal chorus frog ecology and our general understanding of competition between larval anurans.Ecology
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Rogers, Emily Dawn. „Effects of fluoxetine on development and metamorphosis of the African clawed frog, Xenopus laevis“. 2004. http://purl.galileo.usg.edu/uga%5Fetd/rogers%5Femily%5Fd%5F200408%5Fms.
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Thesis (M.S.)--University of Georgia, 2004.Directed by Marsha C. Black. Includes articles submitted to Jorunal of toxicology and environmental health and Environmental toxicology and chemistry. Includes bibliographical references.
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Disbray, Samantha. „More than one way to catch a frog: a study of children’s discourse in an Australian contact language“. 2008. http://repository.unimelb.edu.au/10187/8533.
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Children everywhere learn to tell stories. One important aspect of story telling is the way characters are introduced and then moved through the story. Telling a story to a naïve listener places varied demands on a speaker. As the story plot develops, the speaker must set and re-set these parameters for referring to characters, as well as the temporal and spatial parameters of the story. To these cognitive and linguistic tasks is the added social and pragmatic task of monitoring the knowledge and attention states of their listener. The speaker must ensure that the listener can identify the characters, and so must anticipate their listener’s knowledge and on-going mental image of the story. How speakers do this depends on cultural conventions and on the resources of the language(s) they speak. For the child speaker the development narrative competence involves an integration, on-line, of a number of skills, some of which are not fully established until the later childhood years.The study in this thesis investigates the development of reference tracking in a complex and dynamic language setting. It investigates the language and language development of Warumungu children. The Warumungu central are Indigenous Australians, whose traditional country is in northern Central Australia. Most Warumungu live today in the township of Tennant Creek. Younger people no longer develop full active proficiency in their heritage language, Warumungu, but speak a contact language, Wumpurrarni English as a first language. This contact variety is characterised by substantial variability. In addition to Warumungu and Wumpurrarni English, children learn Standard Australian English, as this is the sole language of instruction in school.
The study describes properties of Wumpurrarni English, in particular nominal expressions, used for tracking reference. These are contrasted with descriptions of the most documented and neighbouring creole variety, Roper River Kriol, and with Standard Australian English. It is demonstrated that in Wumpurrarni English, the marking of new versus given referents on the noun phrase is not obligatory. However a number of structures, such as left dislocation and emphatic subject chaining are used to mark discourse prominence. Repetition of topics, clauses and elements of clauses are stylistic features of a ‘good story’ in Wumpurrarni English.
The study investigates the ways that Warumungu children of different ages introduce, maintain and switch reference, and how, across stretches of their narrations, strategies for managing reference are used. These investigations reveal developmental differences across the age groups in the study, which resonate with studies of children’s narrative competence in other languages, illustrating general cognitive and linguistic development. In addition, some children chose to narrate in a speech style more English-like than they normally use. This set of narrations reveals interesting findings about differences between Wumpurrarni English and Standard English, children’s perceptions of these differences, and insights into the additional cognitive load that speaking in ‘English’ represents.
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Lin, Chia-Hua, und 林佳樺. „Narrative Development of Taiwanese EFL Children: A First Glance at the Children's Story "Frog, Where are you?" in English and Chinese“. Thesis, 2009. http://ndltd.ncl.edu.tw/handle/70799326690195478355.
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碩士國立交通大學
英語教學研究所
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The purpose of the present study was to examine the narrative performance of Taiwanese EFL children in both Chinese and English. The developmental changes in children’s stories across two age groups and the similarities and differences of children’s story structures in the two languages were explored. Twenty-one children from an English-immersion kindergarten program and 22 elementary-school children from an English afterschool program participated in this study. Both groups of children were asked to tell a story in Chinese and English respectively from a wordless picture book, Frog, Where Are You? (Mayer, 1969). Children’s stories were segmented into modified C-units and were further analyzed using the story grammar components (Stein & Glenn, 1979). Each of the children’s story was also categorized into different story grammar levels (Westby et. al., 1984; 1986). The overall descriptive analyses showed that the Taiwanese EFL children of the present study told their Chinese and English stories roughly matched Westby et al.’s eight-stage story grammar (1984; 1986). The preschool children’s narratives mainly fell into three levels: action sequence, reactive sequence, and abbreviated episode; in contrast, the school-aged children’s story levels were more varied, ranging from the simpler story structure such as reactive sequence to more complex structure such as abbreviated episode, complete episode, complex episode, and embedded episode. The cross-age comparisons revealed that the preschool children had lesser ability than the school-aged children in the following aspects: (1) story sequencing, (2) correct information provided, (3) the awareness of psychological states, (4) effective use of repetitions, and (5) story opening and ending. The present study further compared differences of the children’s stories across Chinese and English. The results showed that the children’s English stories contained more incorrect information, and the preschool English stories showed extensive but futile instances of repetitions. In view of the findings, the present study presented a preliminary investigation that examined Taiwanese EFL children’s narrative development in Chinese and English and hoped to provide a preliminary understanding for teachers and parents when they are involved in children’s narrative and language development.
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Edblom, Tara Lynn. „Exposure of northern leopard frog (Rana pipiens) to a pollution gradient in the Green Bay and Fox River ecosystem, Wisconsin (USA) early development, sexual development and impacts of ultraviolet-B radiation /“. 2001. http://catalog.hathitrust.org/api/volumes/oclc/47181675.html.
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Thesis (M.S.)--University of Wisconsin--Madison, 2001.Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 64-67).
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Singhal, Nishant [Verfasser]. „The role of Xenopus BRG1, a conserved subunit of SWI-SNF class of remodeling complexes, during early frog development / vorgelegt von Nishant Singhal“. 2005. http://d-nb.info/976455110/34.
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48
Gould, Anita. „Expression of eph-family receptor tyrosine kinases and ephrins in the tadpole of the frog Xenopus laevis, and possible roles in the development of retinotectal topography“. Thesis, 2001. https://thesis.library.caltech.edu/8117/1/Gould_a_2001.pdf.
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Assembling a nervous system requires exquisite specificity in the construction of neuronal connectivity. One method by which such specificity is implemented is the presence of chemical cues within the tissues, differentiating one region from another, and the presence of receptors for those cues on the surface of neurons and their axons that are navigating within this cellular environment.
Connections from one part of the nervous system to another often take the form of a topographic mapping. One widely studied model system that involves such a mapping is the vertebrate retinotectal projection-the set of connections between the eye and the optic tectum of the midbrain, which is the primary visual center in non-mammals and is homologous to the superior colliculus in mammals. In this projection the two-dimensional surface of the retina is mapped smoothly onto the two-dimensional surface of the tectum, such that light from neighboring points in visual space excites neighboring cells in the brain. This mapping is implemented at least in part via differential chemical cues in different regions of the tectum.
The Eph family of receptor tyrosine kinases and their cell-surface ligands, the ephrins, have been implicated in a wide variety of processes, generally involving cellular movement in response to extracellular cues. In particular, they possess expression patterns-i.e., complementary gradients of receptor in retina and ligand in tectum- and in vitro and in vivo activities and phenotypes-i.e., repulsive guidance of axons and defective mapping in mutants, respectively-consistent with the long-sought retinotectal chemical mapping cues.
The tadpole of Xenopus laevis, the South African clawed frog, is advantageous for in vivo retinotectal studies because of its transparency and manipulability. However, neither the expression patterns nor the retinotectal roles of these proteins have been well characterized in this system. We report here comprehensive descriptions in swimming stage tadpoles of the messenger RNA expression patterns of eleven known Xenopus Eph and ephrin genes, including xephrin-A3, which is novel, and xEphB2, whose expression pattern has not previously been published in detail. We also report the results of in vivo protein injection perturbation studies on Xenopus retinotectal topography, which were negative, and of in vitro axonal guidance assays, which suggest a previously unrecognized attractive activity of ephrins at low concentrations on retinal ganglion cell axons. This raises the possibility that these axons find their correct targets in part by seeking out a preferred concentration of ligands appropriate to their individual receptor expression levels, rather than by being repelled to greater or lesser degrees by the ephrins but attracted by some as-yet-unknown cue(s).
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„Characterization of Mechanisms Influencing Cannibalism Among Larval Amphibians“. Thesis, 2015. http://hdl.handle.net/10388/ETD-2015-10-2286.
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Cannibalism is a seemingly aberrant interaction, appearing counter to the fitness of individuals. Yet cannibalism is not overly uncommon, and naturally occurs among aquatic organisms, including larval amphibians. In temporary wetlands larval amphibians are in a race to complete metamorphosis before their aquatic habitat disappears. When intraspecific competition intensifies, eating conspecifics may represent a beneficial if not necessary strategy. The research presented within this thesis aims to characterize factors that influence cannibalism within populations of larval amphibians. Wood frog tadpoles (Lithobates sylvaticus) were used to test potential benefits of cannibalism as a diet, determine if dietary quality and nutritional stress influence cannibalism, and investigate the roles of competition and chemical cues in influencing cannibalism. Larval long-toed salamanders (Ambystoma macrodactylum), and ringed salamanders (A. annulatum) were used to investigate a functional link between trophic polymorphism and cannibalism in natural populations. Results suggest that perceived increases in competition may stimulate some individuals to become less risk averse, and more aggressive, which may in turn facilitate cannibalistic behaviour. Cannibalism itself provided only conditional benefits to larval wood frogs, rather than the optimal growth that would be expected from an ideal diet. However, this may have been the result of individual variation in response to the diet and/or conspecific cues as opposed to a nutritional deficit. In conditions where tadpoles could perceive increased competition they altered their behaviour and morphology in ways that may improve their foraging success and potentially promote cannibalism. Finally, a functional link appears to exist between head morphology and cannibalism in natural wetlands. However, the appearance of this morphology appears related to conditions that may facilitate increased population densities through rapid pond drying.