Дисертації: "Amphibiens – Physiologie"

1

Renoirt, Matthias. "Influence de l’habitat sur l’écologie et la physiologie du crapaud épineux (Bufo spinosus)." Electronic Thesis or Diss., La Rochelle, 2022. http://www.theses.fr/2022LAROS041.

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Un grand nombre d’études ont mis en avant les effets négatifs des pressions anthropiques dans le temps et dans l’espace sur la biodiversité. Parmi ces pressions anthropiques, les activités et l’expansion agricole jouent un rôle principal dans la modification des milieux et dans la perte de biodiversité. De fait, la question de la persistance des espèces animales dans ce type de milieux se pose. C’est dans ce contexte que ma thèse s’axe. Afin d’étudier les réponses des organismes à un milieu dégradé et les contraintes du paysage sur différents traits d’histoire de vie et l’écologie, je travaille spécifiquement sur une espèce d’amphibien occupant des milieux allant de fortement conservés à fortement dégradés. Afin de comparer les populations de crapauds épineux (Bufo spinosus) forestières et les populations agricoles, j’utilise un vaste panel de marqueurs pour examiner (1) la structure génétique des populations (marqueurs microsatellites), (2) l’écologie alimentaire (isotopes stables), (3) la qualité individuelle (télomères, morphologie, traits de développement) et son impact sur la reproduction. De ce fait et au cours de cette thèse, j’ai pu mettre en relation de nombreux facteurs associés aux paysages agricoles qui soulèvent de nombreuses questions quant au maintien des populations de crapauds épineux. Ainsi, nous avons pu montrer un effet significatif des fertilisants sur la signature isotopique en δ15N des populations de B.spinosus. Aussi, nous avons pu souligner que l’environnement agricole reste suffisamment perméable au maintien de la diversité génétique. Cependant, nous avons mis en évidence de nombreuses contraintes de ce milieu sur la reproduction des populations d’amphibiens, que ce soit par la faible (voir l’absence) abondance de femelles sur les sites de reproduction, et/ou directement sur le succès reproducteur et la qualité de la progéniture. Ces résultats suggèrent de possibles effets à long terme sur les populations d’amphibiens et nous suggérons d’approfondir les différentes voies de recherche que nous suggérons tout au long de cette thèse afin de mieux comprendre les mécanismes sous-jacents à ces résultats et de trouver des solutions quant à la pérennité des espèces sauvages qui n’ont d’autres choix que de s’adapter
A large number of studies have highlighted the negative effects of anthropogenic pressures intime and space on biodiversity. Among these anthropogenic pressures, agricultural activities and expansion play a major role in the modification of environments and in the loss of biodiversity. Questions whether animal species persist in this type of environment arises. My thesis is based on this context. We aimed at study the responses of organism to a degraded environment and the landscape constraints on life history traits and ecology. My work is focused specifically on an amphibian species persisting in habitat ranging from highly conserved to highly degraded by agricultural activities. In order to compare forest and agricultural populations of model species (Spined toad, Bufo spinosus), I relied on a wide variety of markers to examine (1) population genetic structure (micro-satellite markers), (2) feeding ecology (stable isotope), (3) individual quality (telomeres, morphology, developmental traits) and the impact on reproduction. As a result, I was able to connect many factors associated with agricultural landscapes that raised many questions about the persistence of spined toad populations. We were able to show a significant effect of fertilizers on the δ15N isotopic signature of B.spinosus populations. Moreover, we highlighted that agricultural environment allows genetic diversity between populations. However, using correlative approaches, we pointed out various on strains of this environment on the reproduction of amphibians populations, either through low (or no) abundance of females on breeding sites, and/or directly on reproductive success and offspring quality. These results suggest possible long-term effects on amphibian populations, and we suggest that the various avenues of research we suggested throughout this thesis should be pursued in order to better understand the mechanisms underlying these results and to find solutions for the sustainability of wild species that have no choice but to adapt

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2

Bouvet, Jean-François. "Les interactions périphériques entre systèmes trigéminal et olfactif chez les amphibiens : approches immunohistochimique, électrophysiologique et pharmacologique." Lyon 1, 1992. http://www.theses.fr/1992LYO10006.

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Cette these se situe dans le cadre du controle de l'entree sensorielle chez les vertebres. Le premier chapitre etudie l'innervation extrinseque de la muqueuse olfactive; il met en evidence l'existence, chez la grenouille, de fibres trigeminales presentant une immunoreactivite de type substance p et atteignant la surface de l'epithelium. Le deuxieme chapitre s'interesse aux interactions entre systemes olfactif et trigeminal; les effets peripheriques de la stimulation electrique antidromique et la branche ophtalmique du trijumeau sont testes chez les amphibiens. Les principaux resultats enregistres au niveau de l'epithelium olfactif sont representes par une modification de l'activite electrique des neurones recepteurs et une secretion des cellules de soutien. Le troisieme chapitre est consacre aux proprietes pharmacologiques de la muqueuse olfactive. Les effets de l'acetylcholine et de la substance p, qui apparaissent impliquees dans les effets precedemment cites, sont testes sur l'activite electrique de la muqueuse de grenouille. La muqueuse repond avec une grande sensibilite a l'application de l'une ou l'autre de ces deux substances. Ces resultats sont discutes dans une perspective phylogenetique de la reception des differents types de stimulus, odorivecteurs ou modulateurs, par les neurones de l'epithelium olfactif. La discussion generale propose un modele d'activation et d'action du systeme trigeminal de la muqueuse olfactive qui s'integre dans une etude comparative de la regulation peripherique de differents systemes sensoriels chez les vertebres

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3

Figiel, Anne. "Substitution naturelle et induite de l'épithélium intestinal des amphibiens anoures : Aspects cellulaires et moléculaires." Nancy 1, 1989. http://www.theses.fr/1989NAN10158.

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Analyse de l'expression du génome des épithéliocytes intestinaux au cours de la métamorphose naturelle ou induite par la triiodothyronine par électrophorèse bidimensionnelle suivie de fluorographie. La même étude a été réalisée sur les protéines extraites de fractions enrichies en bordure en brosse intestinale au cours de la métamorphose naturelle ou induite ; la villine, protéine du cytosquelette des bordures en brosse a été mise en évidence dans l'intestin des amphibiens. Cette protéine a été purifiée, les caractères et l'expression post-embryonnaire de la villine intestinale d'amphibiens ont été analysés

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4

Cordier-Picouet, Marie-Jeanne. "Organisation du systeme visuel et mise en place de la retinotopie tectale chez les amphibiens anoures." Paris 7, 1987. http://www.theses.fr/1987PA077104.

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5

Morra, Mohamad. "Contribution à l'étude du contrôle de la steroïdogénèse surrénalienne chez les amphibiens : effet et mécanisme d'action de la dopamine." Rouen, 1991. http://www.theses.fr/1991ROUES003.

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L'éventualité d'un contrôle, chez les amphibiens, de la corticostéroïdogénèse par les catécholamines sécrétées par les paraneurones de l'interrénal (surrénale) a été étudiée. En utilisant la technique de périfusion, nous montrons que la dopamine (DA) induit une inhibition dose-dépendante, réversible et reproductible de la production de corticosteroïdes par des tranches d'interrénale de grenouille. La noradrénaline et l'adrénaline sont peu actives. La DA interagit négativement sur la réponse stéroïdienne à l'angiotensine II, tandis qu'elle n'altère pas l'activité corticotrope de l'ACTH ou de la sérotonine. Un effet biphasique, brève stimulation suivie d'une inhibition, est observé lorsque la DA est administrée à des cellules interrénaliennes dispersées. Ces effets stimulateur et inhibiteur seraient médiés respectivement par des récepteurs de type D1 et D2 possédant des caractéristiques pharmacologiques et biochimiques différentes de celles des récepteurs dopaminergiques du cortex surrénalien des mammifères. En particulier, ces récepteurs ne sont pas couplés à l'adénylate cyclase. En revanche, nous montrons que la DA exerce son effet inhibiteur en réduisant l'activité d'une phospholipase C couplée à une protéine G ; cette action se traduit par une réduction de turnover des phospholipides, et consécutivement par une baisse de production d'acide arachidonique et de ses métabolites (prostaglandines). En conclusion, la DA libérée par les paraneurones interrénaliens est susceptible chez les amphibiens d'exercer par voie paracrine un contrôle inhibiteur direct sur la corticosteroïdogénèse

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6

Al-Asaad, Imane. "Étude de marqueurs de différenciation testiculaire Sox9 et Amh lors d'un développement normal, d'une inversion sexuelle et d'un développement en absence de cellules germinales chez l'amphibien urodèle Pleurodeles waltl. Intérêt pour la physiologie comparée de la reproduction des vertébrés." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0229/document.

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Dans le contexte de la physiologie comparée de la reproduction, les amphibiens sont peu étudiés. Le travail réalisé durant cette thèse visait à analyser des marqueurs de différenciation testiculaire chez l'urodèle Pleurodeles waltl, dont le déterminisme génétique du sexe (ZZ/ZW) peut être influencé par la température. Nos études ont d'abord porté sur le gène sox9 marqueur de la différenciation testiculaire chez les vertébrés supérieurs. Le gène cloné chez le pleurodèle montre une bonne conservation par rapport aux autres vertébrés. Son expression plus élevée dans la gonade mâle n'apparaît que tardivement suggérant qu'il n'est probablement pas impliqué dans les stades précoces de la différenciation testiculaire. En outre, son expression dans le mésonéphros rend difficile son utilisation comme marqueur de différenciation testiculaire. Nous avons ensuite étudié l'Amh, hormone testiculaire impliquée dans la régression des canaux de Müller chez de nombreux vertébrés. Son expression spécifique de la gonade, précocement plus élevée chez les larves ZZ que les ZW en font un excellent marqueur de la différenciation testiculaire. Le fait que les pleurodèles mâles voient les canaux de Müller persister malgré la présence d'Amh suggère que la fonction primaire de cette hormone était en relation avec la différenciation gonadique et que la fonction de régression des canaux de Müller n'est apparue que secondairement au cours de l'évolution. Ces marqueurs ont été mis à profit pour caractériser le phénotype gonadique lors d'inversions sexuelles ou lors de développements en absence de cellules germinales. Ils ont permis de montrer que les cellules germinales ne semblent pas jouer de rôle dans la différenciation gonadique du pleurodèle
In the context of comparative physiology of reproduction, amphibians are poorly studied. This work was dedicated to the analysis of testis differentiation markers in the newt Pleurodeles waltl, which shows a ZZ/ZW genetic mode of sex determination that can be affected by temperature. First, we studied sox9, a testis differentiation marker well characterized in many higher vertebrates. The gene cloned in Pleurodeles shows a good level of identity with other vertebrates. The testis-enriched expression appears late during the testis differentiation process indicating that it is probably not involved in the early steps of testis differentiation. Its use as a marker of testicular differentiation proved difficult since it is expressed not only in the gonads but also in the mesonephros. Then, we studied amh, a testis hormone responsible for müllerian duct regression in many vertebrates. Its early expression in the gonad, significantly higher in male than in female larvae makes it an excellent marker for testis differentiation. Since in Pleurodeles waltl, Müllerian ducts persist in males, it suggests that during the course of evolution, the function of Amh on the regression of Müllerian ducts appeared secondarily after its role in gonadal differentiation. These markers have been used to characterize the gonadal phenotype during sex reversal, or in gonads developed in the absence of germ cells. They showed that these cells do not seem to play a role in gonadal differentiation of Pleurodeles waltl

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7

Ouedraogo, Lazare. "Etude de quelques effets de la métamorphose des amphibiens sur certaines protéines et sur la structure hépatique." Paris 13, 1987. http://www.theses.fr/1987PA132022.

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8

Ferrary, Evelyne. "Contribution à l'étude des liquides de l'oreille interne." Paris 11, 1989. http://www.theses.fr/1989PA112058.

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Dans l'oreille interne le labyrinthe membraneux, épithélium neurosensoriel hétérogène, sépare les compartiments endolymphatique et périlymphatique. La composition des liquides contenus dans ces compartiments diffère : l'endolymphe est riche en K, pratiquement dépourvus de Na, et positivement polarisée (quelques mV dans la vestibule) alors que la composition de la périlymphe rappelle celle d'un liquide extracellulaire. L'objet de cette thèse a été d'étudier la composition des liquides de l'oreille interne chez la grenouille et les mécanismes de sécrétion de l'endolymphe dans le canal semi-circulaire. L'étude a éte réalisée sur des hémi-tête de grenouilles sur lesquelles des ligatures on été effectuées afin de séparer les différents segments de l'oreille interne (utricule, ampoule et portion non-ampullaire du canal semi-circulaire postérieur vertical) et sur des canaux semi-circulaire isolés et placés dans une chambre de perfusion. Des techniques de microponctions et de microdosages (Na, K, Cl, osmolalité) ont été utilisées. Les résultats obtenus ont permis de démonter que : i) la composition des liquides labyrinthiques de la grenouille est similaire à celle des liquides des mammifères ; ii) la sécrétion de l'endolymphe est localisée à l'ampoule du canal semi-circulaire par un mécanisme qui dépend de l'activité de la Na+, K+-ATPase, la portion non-ampullaire n'est pas directement impliquée dans les mécanismes de transports necessaires à la sécrétion et au maintien de la composition de l"endolymphe ; iii) le Na est transféré de l'endolymphe vers la cellule par un canal sodique inhibé par l'amiloride ; iv) sur la membrane basolatérale de l'épithélium, la Na+, K+-ATPase et un co-transporteur Na-K-Cl sont impliqués dans les mécanismes de sécrétion de l'endolymphe.

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9

Carey, Marc Brandon. "Brainstem auditory evoked potentials in anuran amphibians." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/4267.

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In this study, I looked at the effects of sound level, temperature and dehydration/hypernatremia on the brainstem auditory evoked potential (BAEP) of four species of anuran amphibians (Rana pipiens, Rana catesbeiana, Bufo americanus and Bufo terrestris). The BAEP was used because it allowed me to monitor both the peripheral and central aspects of auditory nervous function simultaneously and over a long period of time.

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10

Piotrowski, Jeffery Scott. "Physiology, Enzyme Production, and Zoospore Behavior of Balrachochytrium dendrobatidis, a Chytrid Pathogenic to Amphibians." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/PiotrowskiJS2002.pdf.

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11

Palenske, Nicole Marie. "Effects of Triclosan, Triclocarban, and Caffeine Exposure on the Development of Amphibian Larvae." Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc11016/.

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Triclosan and triclocarban are antimicrobials found in numerous consumer products, while caffeine is the most commonly consumed stimulant by humans. This study was undertaken to determine the effects of triclosan, triclocarban, and caffeine on the development and physiology of amphibian larvae. LC50 values of triclosan and triclocarban were determined after 96 hours for three North American larval species: Acris crepitans blanchardii, Bufo woodhousii woodhousii, Rana sphenocephala, and for a common amphibian developmental model: Xenopus laevis. Amphibian larvae were most sensitive to triclosan and triclocarban exposure during early development based upon 96-hour LC50 values. Heart rates for X. laevis and North American larvae exposed to triclosan were variable throughout development. However, significantly lower heart rates were observed in all larvae exposed to triclocarban. Metabolic rates of X. laevis and R. sphenocephala larvae exposed to triclosan were significantly affected in larvae exposed to ½ LC50 and the LC50 concentration. Metabolic rates of X. laevis larvae exposed to triclocarban were significantly affected by exposure to ½ LC50 concentrations in three of four stages investigated. No significant differences were observed in North American larvae exposed to triclocarban. Tissue uptake, lipid uptake, tissue bioconcentration factor (BCF) and lipid BCF of triclosan and triclocarban were investigated in three developmental stages of X. laevis, and in one developmental stage of B. woodhousii woodhousii, and R. sphenocephala. For most tissue and lipid uptake values, a significant increase was observed as exposure concentration increased. Tissue and lipid BCF values were dependent upon both stage and species. Chronic and acute effects of caffeine were determined in X. laevis larvae. Acute 96-hour LC50 values in four developmental stages were > 75,000 ug L-1 caffeine and heart rates were significantly different at the two earliest developmental stages. Larvae chronically exposed to caffeine reached metamorphosis at the same time as controls. Changes in chronic heart rate were dependent upon stage of development and exposure concentration. This research indicates that the toxicity of amphibian larvae exposed to triclosan, triclocarban, and caffeine appears to be dependent upon species and developmental stage, with early developmental stages being most sensitive to contaminant exposure.

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12

Dananay, Kacey Lynn. "ECOLOGICAL AND PHYSIOLOGICAL EFFECTS OF ENVIRONMENTAL STRESSORS ACROSS LIFE-STAGES IN AMPHIBIANS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1528212619441887.

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13

Tufts, Bruce Laurie. "Ion exchange mechanisms for the control of volume and pH in fish and amphibian erythrocytes." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/29443.

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The characteristics of the ion exchange mechanisms which regulate volume and pH in fish and amphibian erythrocytes were investigated and compared. Experiments were carried out under steady state conditions and also following adrenergic stimulation both in vivo and in vitro. Under steady state conditions, a decrease in extracellular pH caused an increase in the volume of rainbow trout erythrocytes, and a decrease in the intracellular pH. These pH-induced volume changes were mainly associated with movements of chloride across the chloride/bicarbonate exchange pathway. The sodium/proton exchange mechanism is quiescent at all pH's studied under steady state conditions. Beta adrenergic stimulation of rainbow trout erythrocytes promoted cell swelling and proton extrusion from the erythrocytes. Amiloride inhibited both the volume and pH changes associated with adrenergic stimulation indicating that this response is associated with an increase in the activity of the sodium/proton exchange mechanism on the erythrocyte membrane. The adrenergic swelling and pH responses are enhanced by a decrease in extracellular pH. An increase in bicarbonate concentration reduces the adrenergic pH response, but it is still significant even at 10 mM bicarbonate. DIDS markedly enhanced the beta adrenergic effect on the erythrocyte pH, but abolished the increase in erythrocyte volume. The adrenergic response was independent of temperature between 10 and 18°C. These results support a loosely coupled sodium/proton and chloride/bicarbonate exchange model for the adrenergic response in rainbow trout erythrocytes. The increases in erythrocyte pH and volume following adrenergic stimulation are associated with increases in the haemoglobin:oxygen affinity. The oxygen carrying capacity of the blood is, therefore, increased following adrenergic stimulation in rainbow trout. Carbon dioxide excretion, however, was not significantly affected by adrenergic stimulation. The functional significance of the adrenergic response of fish erythrocytes may be to offset the effects of the Root shift on the oxygen carrying capacity of the blood during acute changes in extracellular pH. In contrast to fish erythrocytes, the sodium/proton exchange mechanism in amphibian erythrocytes is active under steady state conditions. In the presence of bicarbonate movements, this exchange significantly affects the erythrocyte volume, but not the erythrocyte pH. Similar to fish erythrocytes, protons are passively distributed in amphibian erythrocytes under steady state conditions and in Donnan equilibrium with chloride ions. The erythrocyte volume also increases with decreases in extracellular pH as in fish erythrocytes, due to changes in the chloride distribution across the erythrocyte membrane. Adrenergic stimulation does not affect the volume or pH of amphibian erythrocytes either in vivo or in vitro. These animals, therefore, do not appear to regulate erythrocyte pH adrenergically. Amphibians are able to efficiently utilize oxygen stores via both central and peripheral shunting. In addition, the blood of these animals does not have a Root shift. Adrenergic regulation of erythrocyte pH in order to enhance oxygen transport during fluctuations in ambient and internal gas tensions, therefore, is probably less important than it would be in fish.
Science, Faculty of
Zoology, Department of
Graduate

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14

Kimmel, Peter Blair. "The significance of hypovolemia in dehydrational death in anurans." PDXScholar, 1985. https://pdxscholar.library.pdx.edu/open_access_etds/3432.

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The importance of hypovolemia in dehydrational death was assessed in two anuran species. Xenopus laeyis, a species which experiences a significant reduction in circulating plasma volume with dehydration, was used to evaluate the role of sympathetic reflex compensation in hypovolemia. Adrenergic blockade with propranolol or phenoxybenzamine produced no significant reduction in dehydration tolerance in this species, although β-blockade with propranolol appeared to have a minor effect. The role of hypovolemic shock in the terminal circulatory collapse that precedes death in dehydrating anurans was investigated in the toad, Bufo marinus. The activity of lysosomal proteinases (cathepsins) was used as an indicator of the shock state. An assay was developed for the determination of cathepsin activity in toad plasma and was used to demonstrate the presence of proteinases similar in pH dependence to mammalian cathepsins Bl and D. Plasma cathepsin D-type activity increased with dehydration in toads but was not significantly different from the activity in controls or in toads subjected to splanchnic artery occlusion. Toads appear to maintain plasma volume to 20% water loss at the expense of other extracellular fluids. These results do not support the hypothesis that hypovolemia is a direct cause of dehydrational death in anurans.

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15

Ramelow, Evelyn. "Grundlagen der Verdauungsphysiologie, Nährstoffbedarf und Fütterungspraxis bei Fischen und Amphibien unter besonderer Berücksichtigung der Versuchstierhaltung eine Literaturstudie und Datenerhebung." Berlin mbv, Mensch-und-Buch-Verl, 2009. http://d-nb.info/1002921147/04.

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16

Crossley, II Dane Alan. "The Role of Pulmocutaneous Baroreceptors in the Control of Lymphatic Heart Rate in the Toad Bufo Marinus." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/4892.

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The present study documents that baroreceptors located in the pulmocutaneous artery (PCA) are key components in control of lymph heart rate in amphibians. A negative feedback control loop exists between arterial pressure and lymphatic heart rate. The recurrent laryngeal nerve (rLN), which innervates the PCA baroreceptors, transmits information on arterial pressure to integration centers in the central nervous system. Lymphatic heart rate (LHR) is reduced as a result of increases in arterial pressure. This loop was determined using three experimental protocols. First, the correlation between LHR reduction and hormonally induced vasoconstriction was determined. Increases in arterial pressure due to pressor actions of angiotensin II and arginine vasotocin at high concentrations was negatively correlated to LHR. Second, lymphatic heart rate changes due to natural increases in arterial pressure were compared to rate changes due to increase in arterial pressure after bilateral denervation of the rLN. Post-denervation LHR was not affected by natural increase in arterial pressure prior to the establishment of a new resting arterial pressure. Increase in arterial pressure due to administration of vasoconstricting hormones was negatively correlated with LHR following denervation. Third, the effect on LHR due to direct stimulation of the rLN was studied. Stimulation of the rLN caused LHR to stop without increases in arterial pressure. Presumably, this negative feedback loop is present to limit fluid return to the cardiovascular system from the lymphatic system during periods of acute hypertension. Reduction in the return of lymph volume to the cardiovascular system could eliminate potential damage to pulmonary tissues due to high arterial pressures.

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17

Beauquin, Christophe. "Caractéristiques fonctionnelles des afférences rétino-tectales ipsilatérales chez un amphibien (Rana esculenta) : sensibilité aux stimuli "configurationnels"." Poitiers, 1998. http://www.theses.fr/1998POIT2294.

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Chez la grenouille, les informations retiniennes projetant vers le toit optique ipsilateral utilisent une voie bisynaptique, deux fois croisee. Au sein de cette voie, le noyau isthmique est l'ultime station de relais. L'input ipsilateral retino-tecto-isthmo-tectal (irtt) est compose de deux groupes fonctionnels, les unites i1 et i2, ressemblant respectivement aux cellules ganglionnaires retiniennes r2 et r3. L'etude anatomique de la voie ipsilaterale irtt avec la biotine dextran amine confirme que la projection isthmo-tectale croisee est restreinte aux deux-tiers rostraux, binoculaires, du tectum et que le croisement se situe dans la partie posterieure du chiasma optique. Afin de comparer les systemes ipsilateral et contralateral, l'activite des unites i1 a ete enregistree extracellulairement en reponse a des stimuli mobiles configurationnels - i. E. Des barres noires de longueur croissante (l), orientees dans le sens du mouvement (configuration wl), ou perpendiculairement a la direction du mouvement (configuration awl). Un facteur de discrimination d(w,a), sorte de mesure du contraste entre des barres wl et awl de taille identique, a ete calcule. La sensibilite configurationnelle d(w,a)=f(l) des unites i1 ressemble a celle observee pour les cellules ganglionnaires r3. En outre, elle est invariante avec le niveau d'illumination ambiante et la structure du fond stationnaire. Neanmoins, son profil depend de la vitesse de deplacement du stimulus, et surtout de la largeur des barres wl-orientees. En conclusion, les unites i1 presenteraient les caracteristiques temporelles des cellules ganglionnaires r2, mais les caracteristiques spatiales des cellules ganglionnaires r3. Enfin, la courbe d(w,a)=f(l) represente la sensibilite differentielle d'un neurone visuel pour deux bords orientes verticalement de taille differente plutot qu'une sensibilite differentielle entre deux objets de taille identique mais de configuration differente.

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18

McDearmid, Jonathan R. "Noradrenergic control of spinal motor circuitry in two related amphibian species, Xenopus laevis and Rama temporaria." Thesis, University of St Andrews, 1998. http://hdl.handle.net/10023/15058.

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1. The role of the catecholamine noradrenaline (NA) was examined during fictive swimming in Xenopus laevis tadpoles. 2. The primary effects of the amine in both embryonic and larval Xenopus was to markedly decrease motor frequency whilst simultaneously reducing rostrocaudal delays during swimming. 3. The NA-mediated modulation of swimming activity in Xenopus larvae can be reversed with phentolamine, a non-selective an adrenergic receptor antagonist, suggesting that NA may be acting through either ?1 or ?2 receptors, or a combination of both. 4. Intracellular recordings made from embryo spinal motorneurones revealed that reciprocal inhibitory glycinergic potentials are enhanced by NA. This effect is most prominent in caudal regions of the spinal cord where inhibitory synaptic drive is generally weaker. 5. NA was also found to enhance glycinergic reciprocal inhibition during swimming in larval spinal cord motomeurones. 6. Intracellular recordings, under tetrodotoxin, reveal that NA enhances the occurrence of spontaneous glycinergic inhibitory post synaptic potentials arising from the terminals of inhibitory intemeurones, suggesting that the amine is acting presynaptically to enhance evoked release of glycine during swimming. 7. The effects of NA on swimming frequency and rostrocaudal delay appear to be largely mediated through an enhancement of glycinergic reciprocal inhibition as blockade of glycine receptors with strychnine weakens the ability of the amine affect these parameters of motor output. 8. The effects of NA on motor output were also examined in embryos of the amphibian Rana temporaria. Whilst NA did not obviously affect swimming activity, the amine induced a non-rhythmic pattern of motor activity. 9. The free radical gas, nitric oxide also induced a non-rhythmic pattern of motor discharge that was remarkably similar to that elicited by NA, indicating that this neural messenger may be important for motor control.

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Word, James Mabry. "Physiological adjustments to aestivation and activity in the cocoon-forming frogs Cyclorana platycephala and Cyclorana maini." University of Western Australia. School of Animal Biology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0254.

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The desert-adapted frogs Cyclorana platycephala and Cyclorana maini survive long periods of inhospitably hot and dry conditions by retreating underground and aestivating. While aestivating they suspend food and water intake as well as physical activity, depress their metabolic rate by ~80 %, and form cocoons that protect them against desiccation. How these frogs function during this exceptional state is largely unknown. This work characterized a number of physiological parameters in three metabolic states spanning their natural metabolic range: during aestivation (depressed metabolism), at rest (normal metabolism), and where possible, during exercise (elevated metabolism). The primary objective was to identify by comparison, physiological adjustments in these parameters to metabolic depression, as well as the scope of these parameters in frogs capable of aestivation. The parameters measured for C. maini were (a) the glucose transport kinetics and (b) the fluid balance of an extensive number of their individual organs. For C. platycephala, the parameters measured were (a) the activity of the cardiovascular system as indicated by heart rate and blood pressure and (b) the roles of pulmonary and cutaneous respiratory systems in gas exchange

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20

Pollard, Andrea. "Mechanoadaptation of developing limbs : shaking a leg." Thesis, Royal Veterinary College (University of London), 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.701670.

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21

McLean, David L. "The gaseous messenger molecule, nitric oxide : a modulator of locomotor movements during early amphibian development." Thesis, University of St Andrews, 2001. http://hdl.handle.net/10023/2829.

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1. The free radical gas nitric oxide (NO) is now recognised as a ubiquitous and versatile signalling molecule and the investigation of its biological roles has involved a wide range of scientific disciplines in many different species. Yet despite this, its potential roles in the development of rhythmic motor activities in vertebrates have been largely ignored. 2. Physiological experiments recording extracellular ventral root output suggest that NO is playing an inhibitory role in the swimming system of Xenopus laevis larvae, shortening the duration of swim episodes and slowing swim frequency. Nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry labelled three populations of neurons in the brainstem, which putatively co-localise NO with the aminergic neuromodulators serotonin (5-HT) and noradranaline (NA), and the fast descending inhibitory neurotransmitter, y-aminobutyric acid (GABA). This suggests that the inhibitory role is supraspinal in origin. 3. Intracellular recordings from neurons presumed to be spinal motor neurons provide further evidence for the inhibitory influence of NO. My experiments suggest that NO potentiates both glycinergic and y-aminobutyric acid (GABA)-ergic inhibition onto spinal motor neurons. The facilitation of the release of these inhibitory transmitters is consistent with the observed effects on swim frequency and swim episode duration, respectively. Additionally, NO appears to affect membrane properties, causing a pronounced membrane potential depolarisation and a decrease in membrane conductance. This suggests that NO shuts off a resting membrane conductance. 4. NADPH-diaphorase histochemistry was subsequently applied to determine the four dimensional expression of putative nitrergic neurons in the central nervous system and related structures. The developmental sequence of staining identifies groups and subgroups of interconnected intemeurons, and provides further clues to their identity. NADPH-diaphorase labelling was also located in the eyes, skin and blood vessels, further confirming the validity of this staining technique for identirying nitric oxide synthase. 5. In the related anuran species, Rana temporaria nitric oxide donor drugs appear to have no affect on swimming, but instead reliably initiates a non-rhythmic "lashing" motor pattern similar to that elicited by dimming of the illumination. Interestingly the NADPH-diaphorase technique labelled three clusters of apparently homologous interneurons in the brainstem and additionally the inner layer of the skin was intensely stained, implicating a species-specific role for NO released from brainstem neurons.

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22

Guéguinou, Nathan. "Modifications de l'immunité humorale induites par des changements de la gravité." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0081/document.

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Au cours de ma thèse, j'ai étudié l'impact des stress associés aux vols spatiaux sur l'immunité humorale du pleurodèle et de la souris. Chez le pleurodèle adulte, j'ai d'abord étudié l'utilisation des gènes VH lors de la synthèse des chaînes lourdes d'anticorps suite à une immunisation pendant 5 mois à bord de Mir (expérience Genesis en 1999). J'ai ensuite étudié le processus de maturation de l'affinité des anticorps chez ces mêmes animaux. Ce processus s'effectue par l'apparition d'hypermutations somatiques dans les segments variables des gènes d'anticorps. Ces travaux ont permis de montrer que les segments VH sont utilisés différemment sur Terre et dans Mir et que la fréquence des hypermutations est diminuée suite au vol. Ensuite, j'ai étudié l'impact des stress rencontrés lors d'un autre vol spatial sur la synthèse des premiers anticorps (IgM) chez le pleurodèle en développement (expérience AMPHIBODY en 2006). Le taux d'IgM étant modifié suite à cette expérience, nous avons recréé sur Terre chacun des stress rencontrés en vol (microgravité, hypergravité, choc thermique, radiations, perturbation du rythme circadien et confinement) afin de connaître le(s) stress responsable(s) de cette modification. Ainsi, seule la gravité modifiée affecte l'expression des IgM. Enfin, j'ai étudié l'impact de l'hypergravité (2G et 3G) sur la réponse au stress et le système immunitaire de la souris. Nous avons mis en évidence une réponse physiologique et comportementale au stress à 3G mais pas à 2G. Pourtant, des modifications du système immunitaire sont constatées dès 2G. Cela montre qu'une modification de la gravité, associée ou non à une réponse au stress, affecte le système immunitaire
During my PhD, I studied the impact of spaceflight-associated stresses on Pleurodeles waltl and Mus musculus humoral immunity. In adult P. waltl immunized during 5 months onboard the Mir space station (Genesis experiment in 1999), I first determined how individual VH genes are used. Then, I studied antibodies affinity maturation in these animals. This maturation implies the introduction of somatic hypermutations (SHM) in DNA encoding the variable segments of antibodies genes. These two pieces of work have shown that variable segments of heavy chain gene are differently used and that SHM frequency is reduced when immunization occurs in space. Then, I studied antibodies production during animal development onboard the international space station (ISS) (AMPHIBODY experiment in 2006). The antibodies production being increased in larvae that developed in the ISS, we recreated in the laboratory each stress encountered during the spaceflight (hypergravity, microgravity, heat shock associated to the re-entry in the atmosphere, radiations, perturbation of circadian rhythm and confinement) to determine their impact on IgM heavy chain transcription. This allowed to observe that only gravity changes affect this transcription. Finally, I studied the impact of hypergravity (2G and 3G) on the murine immune system. I observed physiological and behavioural stress responses in mice exposed to 3G but not in 2G mice. However, immune system alterations were observed in both the 2G and 3G groups, suggesting that gravity modifications, associated or not with stress responses, are responsible for immune system modifications

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Parker, Mark. "Independent Acoustic Stimulation of the Amphibian and Basilar Papillae of Rana pipiens." PDXScholar, 1995. https://pdxscholar.library.pdx.edu/open_access_etds/4956.

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This study attempted to selectively stimulate and record from either the amphibian or basilar papillae of Rana pipiens. Computer-generated, frequency-specific clicks were used to elicit BSER's from either amphibian or basilar papillae. Narrowband noise fatiguers were presented in the frequency region of which each papillae are tuned. It was expected that a threshold shift would be elicited in the papillae that received the acoustic trauma, and that no threshold shift would be observed from the collateral papilla. The results of this experiment indicated that there was no overall difference between the threshold shift of either papilla. Furthermore, the amount of AP threshold shift was relatively constant regardless of whether the fatiguer bandwidth was overloading the amphibian or basilar papillae. By contrast, the amount of BP threshold shift was greater when proceeded by a fatiguer with a bandwidth corresponding to the BP tuning region than by a fatiguer with a bandwidth corresponding to the AP tuning region. Additionally, curare maximized the amount of BP threshold shift following fatiguing noise presented with a bandwidth to which the AP is tuned.

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24

Al-Asaad, Imane. "Etude des marqueurs de différenciation testiculaire Sox9 et Amh lors d'un développement normal, d'une inversion sexuelle et d'un développement en absence de cellules germinales chez l'amphibien Pleurodeles waltl. Intérêt pour la physiologie comparée de la reproduction des vertébrés." Phd thesis, Université de Lorraine, 2013. http://tel.archives-ouvertes.fr/tel-00919914.

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Dans le contexte de la physiologie comparée de la reproduction, les amphibiens sont peu étudiés. Le travail réalisé durant cette thèse visait à analyser des marqueurs de différenciation testiculaire chez l'urodèle Pleurodeles waltl, dont le déterminisme génétique du sexe (ZZ/ZW) peut être influencé par la température. Nos études ont d'abord porté sur le gène sox9 marqueur de la différenciation testiculaire chez les vertébrés supérieurs. Le gène cloné chez le pleurodèle montre une bonne conservation par rapport aux autres vertébrés. Son expression plus élevée dans la gonade mâle n'apparaît que tardivement suggérant qu'il n'est probablement pas impliqué dans les stades précoces de la différenciation testiculaire. En outre, son expression dans le mésonéphros rend difficile son utilisation comme marqueur de différenciation testiculaire. Nous avons ensuite étudié l'Amh, hormone testiculaire impliquée dans la régression des canaux de Müller chez de nombreux vertébrés. Son expression spécifique de la gonade, précocement plus élevée chez les larves ZZ que les ZW, en fait un excellent marqueur de la différenciation testiculaire. Le fait que les pleurodèles mâles voient les canaux de Müller persister malgré la présence d'Amh suggère que la fonction primaire de cette hormone était en relation avec la différenciation gonadique et que la fonction de régression des canaux de Müller n'est apparue que secondairement au cours de l'évolution. Ces marqueurs ont été mis à profit pour caractériser le phénotype gonadique lors d'inversions sexuelles ou lors de développements en absence de cellules germinales. Ils ont permis de montrer que les cellules germinales ne semblent pas jouer de rôle dans la différenciation gonadique du pleurodèle.

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Rosendale, Andrew J. "Importance of Facilitative Urea Transporters in Anuran Osmoregulation." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1313089167.

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26

Otani, Lye. "Aspectos da fisiologia metabólica e do desempenho locomotor em anfíbios anuros: implicações da fragmentação ambiental." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/41/41135/tde-12122011-154338/.

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Diversos aspectos metabólicos e comportamentais possuem uma estreita relação com as condições do ambiente, havendo um compromisso entre as condições naturais e a dinâmica de modificações sobre os organismos. Devido ao grande índice de degradação ambiental proveniente da atividade humana nos últimos tempos, populações de anfíbios têm sido particularmente mais afetadas devido a sua alta sensibilidade a alterações ambientais. Em uma paisagem fragmentada, a manutenção de metapopulações viáveis é um importante fator a persistência das populações. Dentro deste contexto, este estudo propõe investigar as relações entre a fragmentação florestal e habilidade das algumas espécies de anuros para se deslocar entre os fragmentos, ou entre estes e corpos d\'água. Assim, realizamos comparações, fisiológicas e comportamentais intra e interespecífica de espécies de anuros residentes em paisagens contínuas e fragmentadas em duas localidades da Floresta Atlântica, com base em suas características morfológicas. De acordo com nossos resultados, as diferenças ambientais entre as paisagens estão relacionadas com as diferenças morfofisiológicas entre as espécies.
In the last few decades, human activity has changed environmental condition, resulting in amphibian populations decline all around the world. In this study we analyze the relationships between forest fragmentation and the ability of some frog species to move between forest fragments or between fragments and breeding sites. Our study focus relies on anuran locomotor performance and supporting physiology, and the relationship between these traits and resistance to forest fragmentation. We compare morphological, physiological and behavioral traits between populations of anurans species living in different landscapes (continuous or fragmented) of two sites in the Atlantic Forest. According to our data, differences in environmental conditions of landscape are related to morpho-physiological traits. This relationship, however, depends on the site of the Atlantic Forest and also varies between species.

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Grimaldi, Alexis. "Interactions croisées entre hormones thyroïdiennes et glucocorticoïdes durant la métamorphose de Xenopus tropicalis." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA11T020/document.

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La métamorphose des amphibiens est le processus rapide et irréversible par lequel un têtard aquatique se transforme en une grenouille respirant à la surface. Cette transition écologique, réminiscente de la période périnatale chez les mammifères, s'accompagne de changements spectaculaires (régime alimentaire, organes locomoteurs, système respiratoire...). Ces modifications morphologiques et physiologiques nécessitent la réponse concertée à un signal hormonal, les hormones thyroïdiennes (HT), de différents tissus vers des destin parfois opposés : apoptose (dans la queue), prolifération (dans les pattes), et remodelage (dans les intestins et le système nerveux central). Toutefois, la synchronisation de la réponse des différents tissus fait appel à d'autres signaux hormonaux, et notamment les glucocorticoïdes (GC). Ces derniers sont également les médiateurs principaux de la réponse au stress. Les processus endocriniens de la métamorphose et la réponse au stress sont fortement couplés. Les GC peuvent ainsi jouer le rôle d'interface permettant l'intégration de signaux environnementaux au niveau de réseaux de régulation. Dans le cadre de mon doctorat, j'ai analysé les transcriptomes des bourgeons de membres postérieurs et de l'épiderme caudal de têtards de Xenopus tropicalis traités ponctuellement avec des HT et / ou des GC. La comparaison de ces deux tissus a permis de caractériser la diversité des profils d'expression des gènes cibles des HT et des GC.Il en ressort plusieurs résultats majeurs. Tout d'abord, la diversité des profils d'interaction entre ces deux voies est limitée, et la majorité des types de profils sont communs aux deux tissus. Indépendamment du tissu, certains profils sont caractéristiques de fonctions biologiques spécifiques comme le remodelage de la matrice extracellulaire et le système immunitaire. Les gènes impliqués dans ces fonctions communes aux deux tissus sont cependant différents. Enfin, plusieurs facteurs impliqués dans la méthylation de l'ADN sont régulés par les deux hormones
Amphibian metamorphosis is the rapid and irreversible process during which an aquatic tadpole transforms into an air breathing adult frog. This ecological transition, reminiscent of the mammalian perinatal period, comes with spectacular changes (diet, locmotor organs, respiratory system...). These morphological and physiological modifications necessitate the properly timed response to a single hormonal signal, the thyroid hormones (TH), in various tissues to lead them to sometimes opposite fates : apoptosis (in the tail), cell prolifération and differenciation (in the limbs) and remodeling (in the intestine and the central nervous system).However, TH do not act alone. In particular, glucocorticoids (GC) play important roles during this process. They also are the main mediator of the stress response. Endocrine processes of the metamorphosis and the stress response are deeply intertwined. GC can thus act as an interface to integrate environmental inputs into regulatory networks.During my doctorate, I analyzed the possible transcriptional crosstalks between TH and GC in two larval tissues : the tailfin (TF) and the hindlimb buds (HLB). Comparing these two tissues allowed me to caracterize the diversity of TH and GC target gene expression profiles. This resulted in several major results. First, the diversity of the profiles of crosstalk between these two pathways is limited, and the majority of the types of profiles is common to both tissues. Next, independently ofthe tissues, some profiles are caracteristic of spécific biological functions such as extracellular matrix remodeling and the immune system. Yet, the genes involved in these shared functions are different between the TF and the HLB. Finally, several factors involved in DNA methylation are subject to a crosstalk between the two hormones

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Mueller, Casey Anne. "Developmental energetics and gas exchange in amphibians and lungfish." Thesis, 2011. http://hdl.handle.net/2440/71323.

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The development of amphibians and fishes is a complex process influenced by intrinsic and extrinsic factors. In this study I examine how energy use and gas exchange contribute to the success and rate of development in two Myobatrachid frogs, Pseudophryne bibronii and Crinia georgiana and the Australian lungfish, Neoceratodus forsteri. 1. Embryonic development of N. forsteri is affected by both temperature and oxygen level. Development time and the cost of development both decreased from 15 to 25°C. At 20°C survival and development rate were highest at oxygen partial pressures (PO₂) of 15 and 20.9 kPa. Hypoxia induced an early hatching age and stage and a decrease in hatchling mass. Breakdown of the vitelline membrane, which is stage-specific and unresponsive to PO₂ or temperature, allowed capsule conductance (GO₂) to increase, promoting oxygen uptake. The inherently low metabolic demand of N. forsteri results in an unusually low cost of development compared to other amphibians and fishes. 2. The partitioning and use of energy throughout development differs between P. bibronii and C. georgiana as modelled using dynamic energy budget theory. The aquatic C. georgiana reaches metamorphosis 1.7 times faster. The species switches energy partitioning at hatching to favour maturation over growth, producing less mass during development than P. bibronii. This appears to be a strategy for fast development, ensuring escape from the ephemeral pools in which C. georgiana develops. Along with faster development, C. georgiana demonstrates greater hypoxia tolerance, as measured by the regulation index. The regulation index, a new method developed to describe hypoxia response, is compared with previous methods, such as the environmental critical PO₂ (PC) and shown to have advantages in describing the relationship between oxygen consumption and environmental PO₂. 3. The development of the perivitelline fluid in amphibians, which occurs as water is absorbed into the egg, can create a significant resistance to gas exchange. In the absence of convection created by cutaneous cilia, oxygen consumption of stage 17 – 19 P. bibronii dropped by 24%. At stage 27 the decline was only 14% due to muscular movements and a greater skin surface area in contact with the egg capsule. 4. Beyond the egg structures, oxygen transfer is strongly influenced by developmental gas exchange organs such as the skin and internal gills. Despite only taking 27 days to reach stage 27, compared to 39 days in P. bibronii, C. georgiana shows no significant adaptations in cardio-respiratory morphology that promote faster development. The species are similar in overall body volume and surface area and the skin is the major site for diffusive gas exchange, with the internal gills supplementing oxygen transfer, in both species. P. bibronii has a larger heart and greater internal gill tissue, but the volume of internal gill capillaries is the same. Rather than having a current function for gas exchange, the larger heart may function to promote the development of capillaries in the internal gills to match the greater larval growth of P. bibronii from stage 27.
Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2011

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Piotrowski, Jeffery Scott. "Physiology, enzyme production, and zoospore behavior of ba trachochytrium dendroba tidis, a chytrid pathogenic to amphibians /." 2002. http://www.library.umaine.edu/theses/pdf/PiotrowskiJS2002.pdf.

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30

Chiavarini, Katherine E. "Rapid effects of corticosterone on stress-related behaviors in an amphibian." Thesis, 1997. http://hdl.handle.net/1957/33782.

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In the wild, when an animal is exposed to predators or harsh conditions, the stress response is often associated with fleeing behaviors, which are seen as increased locomotor behavior. Handling-stress procedures and intracerebroventricular (icy) injection of corticotropin-releasing factor (CRF) have both been shown to cause an increase in locomotor activity in roughskin newts (Taricha granulosa). The present experiments were designed to determine if icv administration of corticosterone (CORT) prevents stress-induced locomotor increases in activity, if it prevents CRF-induced increases in locomotor activity, and if the time-course and pharmacological specificity of the CORT effects on locomotor activity fit the model for intracellular or membrane receptors. In experiment 1, newts which had been injected with CORT or dexamethasone (DEX) received a standardized handling-stress procedure. Corticosterone administration was able to suppress the increase in locomotor activity in newts exposed to handling-stress at 20 minutes after administration. This effect was transient (no longer present at 2 hours after the injection) and not mimicked by DEX, a synthetic glucocorticoid that binds to intracellular and not membrane receptors. In experiments 2 and 3, either CORT or DEX was administered in the same icy injection with CRF. CORT suppressed CRF-induced locomotor activity in some cases, but this action of CORT seems to be context dependent. Results for DEX-injected newts were confounded the failure of CRF to induced significant increases in locomotor activity. There was variability in the effect of CRF on locomotor activity across seasons. Based on time-course and specificity, it appears that CORT can modulate locomotor activity in newts through mechanisms involving the membrane receptor. Variability in the effects of CRF on locomotor activity in newts suggests there may be seasonal differences in responses to stress.
Graduation date: 1998

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31

Lowry, Christopher. "Neurobiology of stress : central actions of corticotropin-releasing factor in an amphibian." Thesis, 1995. http://hdl.handle.net/1957/34605.

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32

Nguyen, Long Thanh. "A study of the role of glycogen in skeletal muscle performance and of myosin heavy chain isoform expression in amphibian skeletal muscle using the toad Bufo marinus." Thesis, 2000. https://vuir.vu.edu.au/15310/.

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The overall aim of this study was to contribute knowledge to two areas of inquiry in muscle research: one concerned with the molecular mechanism(s) underlying the positive correlation between intracellular glycogen content and skeletal muscle performance and the other with the MHC isoform composition in amphibian skeletal muscle and single muscle fibres. The organism used throughout this study was the cane toad Bufo marinus.

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Thurman, Lindsey L. "Elevational differences in UV-B response by the long-toed salamander (Ambystoma macrodactylum)." Thesis, 2012. http://hdl.handle.net/1957/30208.

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Global amphibian declines have been attributed to numerous and often synergistic causes, such as invasive species, pathogens, and ultraviolet-B (UV-B) radiation. The effects of these stressors are context dependent and can vary with location, species, and populations. As sensitivity to UV-B has shown inconsistencies across amphibian taxa, it can be expected that variation also occurs between populations of a single species. High elevation populations of the long-toed salamander (Ambystoma macrodactylum) face exponentially higher UV-B radiation levels relative to low elevation populations and these levels are predicted to increase in conjunction with continued ozone depletion. We hypothesized that breeding long-toed salamander females at high elevations have modified oviposition behavior to better protect embryos from UV-B induced damage. In addition, we hypothesized that long-toed salamander embryos at high elevation would exhibit elevated photolyase activity, a photo-reactivating enzyme that repairs UV-B radiation-induced damage to DNA. We predicted that this behavioral defense strategy would be employed together with an elevated physiological response as a correlated defense response to increased levels of UV-B radiation in high elevation populations. We surveyed high and low elevation long-toed salamander breeding sites throughout Oregon to quantify oviposition site characteristics and associated UV-B profiles. We simultaneously collected embryos for quantification of photolyase activity in a bacterial transformation assay. We found significant differences in oviposition behavior across elevations, with high elevation breeding females ovipositing in deeper water and using UV-B protective refugia. Oviposition sites at low elevations, however, were most often found in UV-B exposed microhabitats located at the surface of the water. This population difference in oviposition behavior resulted in a standardization of UV-B and temperature conditions for long-toed salamander embryos across elevation. In contrast, we found no population differentiation in photolyase activity between high and low elevation breeding sites. This indicates that behavioral selection for UV-B protected oviposition substrates may either be negating the need for increased photolyase activity in long-toed salamander embryos, or that populations lack the capacity to adapt a heightened physiological response to UV-B at high elevations. Together, these results show how trade-offs in physiology and behavior are a unique adaptation to a significant environmental stressor. Further research into the susceptibility of amphibian species to changing environmental conditions may help to demonstrate the effectiveness of correlated trait responses and plasticity in behavior, and species persistence under changing climate regimes.
Graduation date: 2012

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Дисертації з теми "Amphibiens – Physiologie"

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