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Amphibian and Reptile Trade in Texas: Current Status and TrendsPrestridge, Heather L. 2009 August 1900 (has links)
The non-game wildlife trade poses a risk to our natural landscape, natural
heritage, economy, and security. Specifically, the trade in non-game reptiles and
amphibians exploits native populations, and is likely not sustainable for many species.
Exotic amphibian and reptile species pose risk of invasion and directly or indirectly alter
the native landscape. The extent of non-game amphibian and reptile trade is not fully
understood and is poorly documented. To quantitatively describe the trade in Texas, I
solicited data from the United States Fish and Wildlife Service's (USFWS) Law
Enforcement Management Information System (LEMIS) and Texas Parks and Wildlife
Department's (TPWD) non-game dealer permits. I surveyed amphibian and reptile pet
owners, breeders, Internet sites, pet shops, and meat and seafood establishments by
visits, electronic surveys, and observations.
The trade in exotic species of amphibians and reptiles in the state of Texas was
found to be popular in two ways; the importation of wildlife products and sale of live
specimens for pets. Persisting in the pet trade were species known to be exotic, a
problem made worse by lack of regulations governing the import, export, and keeping of exotic species. Trade in wild collected native species was primarily for export to foreign
countries. Collection of turtles from the wild in Texas was heavy until 2008, when
TPWD restricted collection to private waters. Collection of other species from the wild
was minimal, with the exception of the Western Diamond-backed Rattlsnake (Crotalus
atrox) for rattlesnake roundups. Native species were found to exist in the pet trade, but
primarily as genetic color variants that do not occur in the wild, an indication that
captive breeding may be relieving pressures on wild caught specimens.
Minor changes in reporting requirements and permitting systems at the state and
federal level would improve the management of exotic and native amphibians and
reptiles that persist in the trade. Changes that include standardized taxonomic reporting
requirements at state and federal level, streamlined permitting system for individuals
wishing to collect from the wild in Texas, bag limits and seasons for wild collection,
increased reporting requirements for owners of exotics, and enforcement of reporting
errors would aid in management of exotic and native amphibians and reptiles in the
trade.
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Ecophysiology of Australian cocooning and non-cocooning, burrowing, desert frogsMcMaster, Kellie Anne January 2007 (has links)
[Truncated abstract] This thesis explores the ecophysiology of cocooning and non-cocooning Australian burrowing desert frogs in order to specify the details of these two alternative survival strategies. Many details of these life-history strategies have not previously been determined for Australian frogs. In this study the detailed method of function and formation of the cocoon itself was investigated for the first time, as were the moulting cycles, which drive cocoon formation. Cocooning species had consistently shorter inter-moult-periods than non-cocooning species, which is presumably adaptive, allowing production of cocoon layers at a faster rate. Transmission electron microscopy revealed cocoon formation in Cyclorana platycephala to be a plastic, rather than static adaptation. The initial stages of cocoon formation appear to be the most critical. Cocoon layer formation is fastest in the first month and the initial layers produced are thicker than subsequent layers. Also, only in this initial stage does layer thickness appear to be influenced by soil moisture. Scanning electron microscopy confirmed the lips, eyelids and cloaca of cocooned frogs to be sealed by continuous layers of cocoon. However, it remains unclear precisely how the continuous junctions between cells from discreet sources, such as the upper and lower lip, are formed. Measurements of evaporative water loss and resistance over various relative humidity gradients suggested that water content within the cocoon structure is very low unless the external RH is > 93%. Therefore, anuran cocoon is confirmed to function as a specialised and highly effective barrier to water diffusion in arid-zone frogs. ... Within a dune swale, N. aquilonius burrows were an average depth of 1.13 m in loamy sand (clay = 6%, silt = 7%). Neobatrachus aquilonius excavated from the claypan had well formed cocoons, while those found in the dune swale had only one or two thin layers, indicating cocoon formation had only just commenced, although the last rainfall had been over six months prior. This suggests that N. aquilonius is able to switch between the cocooning and non-cocooning strategy in different soil types and different conditions. In summary, cocoon formation was found not to be an entirely passive accumulation of layers. Cocoon formation involved specialisation in the rate and thickness of epithelial layer production and the sealing of layers over lips, eyes and cloaca. Moreover, the cocoon was confirmed to operate effectively as a diffusion barrier at all except the highest external relative humidity. Like cocoon-forming species, Notaden nichollsi was found to metabolically depress to survive for longer periods underground. However, they cannot survive for the entire period
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Systematics of Coccidian Parasites (Apicomplexa) from Amphibians and Reptiles in Northcentral TexasMcAllister, Chris Thomas 12 1900 (has links)
Between February 1986 and October 1988, 863 amphibians and reptiles were collected in northcentral Texas and examined for coccidial parasites. Thirteen percent of amphibians <26% salamanders, 11% frogs and toads) and 28% of reptiles (54% turtles, 25% snakes) harbored 20 previously described and 16 new species of coccidia; overall prevalence of infection was 176/863 < 20%). Sixteen Ambvstoma texanum were infected with Eimeria ambystomae which represents new host and geographic locality records for the coccidium. Forty anurans were found to be passing coccidia, including Pseudacris streckeri. Bufo valliceos and Gastrophryne olivacea. Four new species of coccidia were described from anurans and include Eimeria flexuosa. E. streckeri. Isospora dellcatus and I_. fraaosum. However, oocysts found in B. v.. valliceps were determined experimentally to represent pseudoparasites. Sixty-eight turtles were infected with coccidia, including Chelvdra serpentina, Kinoeternon flavescens. Pseudemvs texana. Terrapeng ornata and Trachemvs scripta eleoans. Fourteen eimerians (5 of which are described as new species) were found in turtles. The new species from turtles include Eimeria cooteri, E. ornata, E. Btvlosa. E. texana and E. trachemvdis. Interestingly, all 96 lizards examined were negative for coccidia. Fifty-three snakes including 11 colubrids and 1 viperld harbored coccidia of the genera Caryospora. Cryptosporidium. Eimeria and Sarcocystis: prevalence of infection was highest in 3 species of North American water snakes <Nerodia spp.). Seven new species of Eimeria were described from snakes, including E. conanti. E. lnfirmus. E. papillosum. E. rhombifera. E. serpenticola. E. striatula and E. tenuis. There was no preference for coccidia between the sexes of any hosts. Based on limited data from a single anuran host, prevalence was higher during wetter months of spring than in summer. In addition, prevalence was higher in aquatic and semiaquatic snakes than in truly terrestrial species. Preliminary data suggested that using host specificity data of coccidia may be a method of studying host phylogeny and coevolutionary relationships in thamnophiine snakes.
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Independent Acoustic Stimulation of the Amphibian and Basilar Papillae of Rana pipiensParker, Mark 07 July 1995 (has links)
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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Introduced bullfrogs (Rana catesbeiana) in British Columbia : impacts on native Pacific treefrogs (Hyla regilla) and red-legged frogs (Rana aurora)Govindarajulu, Purnima. 10 April 2008 (has links)
No description available.
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Methodological assessment of the Critical Thermal Maximum (CTmax) of anuran larvae: interaction among the experimental heating rates, ontogeny and body mass / Estudo metodológico da Temperatura Crítica Máxima (CTmax) de larvas de anfíbios anuros: interação entre as taxas de aquecimento experimental, ontogenia e massa corpóreaCantero, Gustavo Adolfo Agudelo 31 October 2016 (has links)
Thermal limits for ectothermic animals displays a picture of the range of body temperatures that is tolerable by individuals before their locomotory capacity is impaired. However, thermal limits are not fixed and specific traits, but labile ones subjected to plastic adjustments and evolutionary change, and also are influenced by intrinsic and extrinsic factors of organisms, as well as by methodological factors inherent to experimental protocols. Even more, the influences of these factors on thermal limits have been commonly addressed independently in different taxa, and the extent by which multiple factors interact and affect thermal limits within taxa is poorly understood. Thus, the main aim of this work was to conduct a methodological assessment of the Critical Thermal Maximum (CTmax) by studying the influences of different experimental heating rates (ΔT’s), ontogeny, body mass, and the interaction among these factors on this trait. This matter was addressed on larvae of Physalaemus nattereri and Hypsiboas pardalis, two anuran species from the São Paulo State, southeastern Brazil, that differ in their phylogenetic background, ecological and life-history characteristics and inhabit environments with different thermal regimes. First, ΔT’s did affect averages and variances of CTmax in a species-specific manner. In addition, it was found a ΔT-dependent decreasing in CTmax at the end of metamorphosis in tadpoles of P. nattereri, because only the metamorphosing tadpoles exposed to the acute ΔT were more sensitive to high temperature than premetamorphic tadpoles. Finally, body mass and ΔT’s interacted on the CTmax of both species along our experimental design. In P. nattereri, body mass affected CTmax through physiology at the slow ΔT’s, whereas in H. pardalis body mass affected CTmax at the acute ΔT through a methodological artifact driven by higher thermal inertia in the group of large tadpoles. This study revealed that ΔT’s, ontogeny and body mass interact on the CTmax of our studied species, and these interactive effects could not have been elucidated by the independent study of each factor. It also highlights the importance of integrating the factors that influence thermal limits of ectothermic animals, especially in the context of climate change / Os limites térmicos para animais ectotérmicos mostram uma imagem do intervalo de temperaturas corporais que é tolerável pelos indivíduos antes de sua capacidade locomotora ser prejudicada. Porém, os limites térmicos não são características fixas e específicas, mas traços lábeis sujeitos tanto a ajustes plásticos quanto a mudanças evolutivas, e são influenciados por fatores intrínsecos e extrínsecos dos organismos, e também por fatores metodológicos associados aos protocolos experimentais. Ainda mais, as influências desses fatores sobre os limites térmicos têm sido comumente abordadas de forma independente em diferentes espécies, e o grau pelo qual múltiplos fatores interagem e afetam os limites térmicos dentro das espécies é pouco compreendido. Assim, o principal objetivo deste trabalho foi conduzir uma avaliação metodológica da Temperatura Crítica Máxima (CTmax) estudando as influências de diferentes taxas de aquecimento experimental (ΔT’s), ontogenia, massa corpórea e a interação entre esses fatores sobre esta característica fisiológica. Este assunto foi abordado em larvas de Physalaemus nattereri e Hypsiboas pardalis, dois espécies de anfíbios anuros encontrados no Estado de São Paulo, sudeste do Brasil, que diferem em sua origem filogenética, características ecológicas e de história de vida, e também habitam ambientes com diferentes regimes térmicos. Primeiro, foi encontrado que as ΔT’s afetaram tanto os valores médios quanto as variâncias da CTmax em ambas as espécies de maneira específica. Além disso, achou-se uma diminuição em CTmax no final da metamorfose que foi dependente da ΔT em larvas de P. nattereri, dado que nessa espécie só os girinos em metamorfose que foram expostos à ΔT aguda foram mais sensíveis às altas temperaturas do que os girinos premetamórficos. Finalmente, a massa corpórea e as ΔT’s interagiram sobre a CTmax em ambas as espécies ao longo do desenho experimental. Em P. nattereri, o efeito da massa corpórea sobre a CTmax foi fisiológico nas ΔT’s lentas, enquanto que em H. pardalis o efeito da massa corpórea na ΔT aguda foi devido a um artefato metodológico causado por maior inércia térmica no grupo de girinos maiores. Este estudo revelou que as ΔT’s, a ontogenia e a massa corpórea interagem sobre a CTmax das espécies estudadas, e estes efeitos interativos não poderiam ter sido elucidados pelo estudo independente de cada fator. Também é salientada a importância de integrar os fatores que influenciam os limites térmicos dos animais ectotérmicos, especialmente no contexto das mudanças climáticas
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Estratégias fisiológicas e comportamentais em anuros no semiárido: implicações sobre o balanço energético e hídrico / Physiological and behavioral strategies in frogs in the semiarid: implications on the energy and water balancePereira, Isabel Cristina 13 June 2016 (has links)
A estivação é caracterizada como um conjunto de alterações fisiológicas e comportamentais relacionadas com a redução do metabolismo e a permanência em micro-habitats específicos durante a fase de estiagem. Na caatinga brasileira foram observadas ao menos três espécies que estivam, sendo duas da família Leiuperidae, Pleurodema diplolistris e Physalaemus albifrons e uma da família Cycloramphidae, Proceratophrys cristiceps. Ainda que encontradas no mesmo micro-habitat durante a estivação, estas três espécies exibiram padrões distintos de alteração do desempenho locomotor entre as duas estações marcantes do ano (seca e chuvosa). Enquanto P. diplolistris reduziu em cerca de 47% a velocidade de seu desempenho locomotor durante a fase de estiagem, as outras duas espécies, P. cristiceps e P. albifrons, reduziram cerca de 87 e 83%, respectivamente. Mais ainda, apenas P. diplolistris exibiu mudança de profundidade ao longo da estiagem. A redução da taxa metabólica aeróbia foi de aproximadamente 50% para as três espécies. A comparação entre as estações marcantes do ano ainda revelou que as três espécies estudadas apresentam diferentes padrões de alteração na concentração de substrato energéticos e na atividade de enzimas representativas do metabolismo energético no fígado e musculatura dos membros posteriores. A manutenção hídrica também foi diferente entre as três espécies, o que indica a ocorrência de estratégias diversas de regulação hídrica / Estivation is defined as a set of physiological and behavioral changes associated to decreased metabolism and permanence in specific microhabitats during the dry season. In the Brazilian Caatinga was observed at least three estivating species: Pleurodema diplolistris and Physalaemus albifrons (Leiuperidae) and Proceratophrys cristiceps (Cycloramphidae). Although found in the same micro-habitat during aestivation, these three species differ in the variation patterns of locomotor performance when compared between the two seasons (dry and rainy season). During the dry phase, speed in P. diplolistris is reduced by about 47% whereas in P. cristiceps and P. albifrons values decrease by 87% and 83%, respectively. Moreover, only P. diplolistris exhibited changes of depth along the drought. The reduction of aerobic metabolic rate was of approximately 50% for the three species. The comparison between seasons also revealed that the three species differ in relation to the variation patterns of the concentration of substrate energy and activity of representative enzymes of energy metabolism in the liver and muscles of the hindlimb. The water maintenance was also different among the three species, indicating the occurrence of several strategies of hidric regulation
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Relação entre preferência termal, taxa metabólica e desafio imunológico por lipopolissacarídeo de bactéria gram-negativa (LPS) em Rhinella icterica (Anura: Bufonidae) / Relationship between preferred temperature, metabolic rate and lipopolysaccharides of gram-negative bacteria (LPS) immune challenge in Rhinella icterica (Anura: Bufonidae)Moretti, Eduardo Hermógenes 15 April 2016 (has links)
Anfíbios tem a habilidade de manifestar febre comportamental em ambientes heterotermais durante infecção a um custo metabólico associado à elevação da temperatura corpórea e à ativação do sistema imune. Apesar do custo metabólico, a temperatura corpórea febril otimiza a resposta imune no combate à infecção e aumenta as chances de sobrevivência do indivíduo. Contudo, devido à limitada capacidade de termorregular, os anfíbios enfrentam variações diárias e sazonais na temperatura corpórea e na resposta metabólica de reação à infecção. O nosso objetivo foi medir a variação da resposta metabólica à infecção dentro da variação de temperaturas ecológicas relevantes do sapo Cururu. Testamos a hipótese de que a infecção aumenta as taxas metabólicas do sapo Cururu, mas o custo energético da resposta imune deve ser menor na temperatura febril dos sapos infectados. Para testarmos as hipóteses, nós medimos a temperatura operacional dos sapos no campo, a preferencia termal dos sapos hígidos e a temperatura preferencial dos sapos infectados. Depois, medimos a taxa metabólica e a resposta metabólica dos sapos antes e depois da infecção por LPS nessas temperaturas. Nossos resultados mostraram que as temperaturas ecológicas relevantes dos sapos variaram entre 17°C e 26°C. A temperatura influenciou a taxa metabólica dos sapos, mas só na temperatura preferencial dos sapos hígidos houve custo metabólico associado à infecção. Contudo, na temperatura corpórea dos sapos infectados a resposta metabólica de reação à infecção foi menor, indicando que o controle regulado no ponto de ajustes \"set-point\" da temperatura corpórea durante a infecção coevoluiu com um custo energético otimizado da resposta imune / Anphibians have the ability of manifested behavioral fever in heterothermal environments during infection with a metabolic cost associated to elevated body temperature set-point and due to activation of immune system. Despite the metabolic cost, fever body temperature optimizes immune response to combat infection and increase the survival of the host. However, because of the limited capacity for thermoregulation, amphibians can confront daily and seasonal variation in body temperature and in the metabolic response of reaction to combat infection. So, we measured the variation in metabolic response of reaction to infection at ecology relevant body temperature range in Cururu toads. We hypothesized that infection increases metabolic rates of the Cururu toads due to the activation of the immune system at different temperatures, but the energetic cost of immune response is lower at preferred body temperature of infected toads (behavioral fever). To test these hypotheses we measured the operative body temperature in the field, the preferred body temperature of higid toads, and the preferred body temperature of infected toads. After, we measured metabolic rate and metabolic response of the toads before and after injection of LPS at these temperatures. Our results showed that the ecology relevant temperature range of Cururu toads (R. icterica) varies between 17°C and 26°C, respectively, at operative temperature and at preferred body temperature in infected toads when exposed to heterothermal environment. The temperature had the major impact on metabolic rate of the toads during infection. But, at fever body temperature toads decrease the metabolic response of reaction to infection, indicating that the regulated control of body temperature set-point during infection coevolved with an optimized energetic cost of immune response
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Estudo sobre respostas comportamentais à infecção no anfíbio anuro Proceratophrys boiei / A study of behavioral responses to infection in the anuran amphibian Proceratophrys boieiOlarte, Laura Camila Cabanzo 10 August 2017 (has links)
Esta tese tem como tema central o conceito de febre comportamental, que tem-se definido como o aumento da temperatura corporal pela efetivação da mudança nas temperaturas preferidas devido ao reconhecimento, por parte do corpo, de uma infecção ou patógeno. O trabalho está composto por três partes. Na Introdução Geral é discutida a febre comportamental em sete pontos fundamentais no entendimento desta resposta dentro da Ecofisiologia, começando pela definição, as pesquisas de laboratório e campo existente até o momento, até as limitações ecológicas dos indivíduos e as implicações do tema na conservação. No capítulo 1, com formato de texto científico, apresentamos a pesquisa na qual estudamos o comportamento e a preferência termal da espécie Proceratophrys boiei em condições experimentais com indivíduos injetados com lipopolisacáridos (LPS), para simular uma infecção, e indivíduos intactos (injetados com salina, grupo controle). Nessa pesquisa consideramos duas alternativas de respostas no comportamento, tal como discutido na introdução geral: a) febre comportamental, que é caracterizada por um aumento da temperatura corporal dos indivíduos pela mudança nas temperaturas preferidas dentro de uma paisagem termal; b) comportamento de doente, que no contexto do desenho experimental seria reconhecido pela diminuição da atividade dos indivíduos. Assim, registramos os seguintes tratamentos durante 24 horas com uma câmara termográfica: 1) indivíduos intactos no gradiente termal desligado, 2) indivíduos intactos no gradiente termal ligado, 3) indivíduos injetados com salina, no gradiente termal ligado 4) indivíduos injetados com LPS no gradiente termal ligado. Para cada um dos tratamentos foi registrada a distância de locomoção e as preferências termais, junto com outros detalhes do comportamento e as preferências termais. A partir de nossos resultados, concluímos que os indivíduos de P. boiei apresentam comportamento de doente como resposta dominante ao ser injetados com LPS, e que as preferências termais destes são consequência do comportamento de doente e não da termorregulação comportamental. Finalmente, a discussão geral explica como o capitulo 1 contribui na discussão de cada um dos sete pontos tratados na introdução geral tentando propor metodologias e estudos mais completos para manter o diálogo entre a fisiologia e a ecologia dos indivíduos no contexto de infecção e doenças / The central theme of this thesis is the concept of behavioral fever, which has been defined as the increase of body temperature by effecting the change in preferred temperatures due to the recognition by the body of an infection or pathogen. The thesis is composed of three parts. In the General Introduction, behavioral fever is presented around seven fundamental points to the understanding of this response within Ecophysiology, starting with the definition, the laboratory and field research until now, to the ecological limitations of individuals and the implications of this theme in conservation. In the first chapter, with scientific text format, we present the research in which we studied the behavior and thermal preference of Proceratophrys boiei species under experimental conditions in individuals injected with lipopolysaccharides (LPS), to simulate an infection, and in intact individuals (injected with Saline, a control group). In this research we considered two alternatives of behavioral responses, as discussed in the General Introduction: a) behavioral fever, which is characterized by an increase in the individuals body temperature by changing the preferred temperatures within a thermal landscape; B) patient behavior, which, in the context of experimental design, would be recognized by the decrease in the activity of individuals. Thus, we recorded the following treatments for 24 hours with a thermographic camera: 1) intact individuals in the thermal gradient switched off, 2) intact individuals in the connected thermal gradient, 3) individuals injected with saline, in the bound thermal gradient 4) individuals injected with LPS in the thermal gradient on. For each of the treatments it was recorded the locomotion distance and the thermal preferences, along with other details of the behavior and the thermal preferences. From our results, we conclude that the individuals of P. boiei present a patient\'s behavior as a dominant response when injected with LPS and their thermal preferences are a consequence of patient behavior and not behavioral thermoregulation. Finally, the general discussion explains how chapter 1 contributes to the discussion of each of the seven points highlighted in the general introduction attempting to propose a complete methodology and studies to maintain the dialogue between the physiology and the ecology of individuals in the context of infection and disease
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Tolerância ao congelamento em algumas espécies de anuros de América do Sul: mecanismos e estratégias / Freeze tolerance in some frogs of South America: mechanisms and strategiesFernandez, Juan Manuel Carvajalino 14 August 2017 (has links)
Os limites geográficos que marcam o risco de congelamento são determinantes na biodiversidade de anfíbios. Os mecanismos fisiológicos envolvidos na preparação e reação aos eventos de temperatura extrema são específicos e dependem da previsibilidade e repetitividade destes eventos. Na América do Sul, existem regiões com risco de congelamento para os anfíbios, contudo pouco se conhece da tolerância ao congelamento em espécies endêmicas deste continente. O doutorado foi elaborado em locais com reportes de congelamento na Argentina e o Brasil, usando como modelo as espécies Alsodes gargola, Bokermanohyla gouveai, Dendrosophus minutus, D. microps, Hypsiboas latistriatus, H. polytaenius, Melanophryniscus moreirae, Pleurodema bufoninum, Ologygon brieni, Scinax duartei e S. hayii, avaliando exposição potencial ao congelamento em refúgios termais, sobrevivência a temperatura congelante, mudanças em moléculas com função crioprotetora (colesterol, glicose, proteínas, triglicérides, ureia) e crescimento de gelo corporal. Dentro deste contexto, a minha hipótese geral foi que existem anfíbios que sobrevivem ao congelamento na América do sul e que estas espécies presentam mecanismos de resposta fisiológica que deveriam variar entre espécies em um evento de congelamento controlado. No decorrer do doutorado esta hipótese foi corroborada, encontrando sobrevivência a temperatura congelantes nas especies A. gargola, B. gouveai, D. microps, H. latistriatus, H. polytaenius, M. moreirae, P. bufoninum, S. duartei e S. hayii, sendo que existe uma amplia variedade de estratégias fisiológicas para fazer frente ás baixas temperaturas. Entre as espécies anteriormente reportadas, definiu-se que D. microps, H. polytaenius, P. bufoninum, S. duartei e S. hayii, são tolerantes ao congelamento devido a que apresentarem tanto acumulo de crioprotectores como crescimento de gelo corporal durante a exposição a baixas temperaturas. Por outro lado usando analises filogenéticos, conseguiu-se reforçar a hipóteses que a tolerância ao congelamento é convergente ao longo da historia evolutiva dos anfíbios, acontecendo independentemente em vários clados. As novas descobertas sobre a riqueza fisiologia no nível de adaptações frente ao congelamento em América do Sul são apenas pequenas amostras do que potencialmente pode ser achada pensando na biodiversidade existente neste continente, logo a presente tese, é só um incentivo para futuros trabalho na área / The geographical boundaries that mark the risk of freezing are determinants for amphibian biodiversity. The physiological mechanisms involved in the preparation and reaction to extreme temperature events are specific and depend on the predictability and repeatability of these events. In South America, there are regions with freezing risk for amphibians, however little is known about the freezing tolerance in endemic species to this continent. The present doctoral dissertation was prepared in places with freezing reports in Argentina and Brazil, using as biological models the species Alsodes gargola, Bokermanohyla gouveai, Dendrosophus minutus, D. microps, Hypsiboas latistriatus, H. polytaenius, Melanophryniscus moreirae, Pleurodema bufoninum, Ologygon brieni, Scinax duartei and S. hayii, evaluating potential exposure to freezing in thermal refuges, survival to freezing temperature, changes in cryoprotectant molecules (cholesterol, glucose, proteins, triglycerides, urea) and body ice growth. Within this context, my general hypothesis was that there are amphibians that survive freezing in South America and that these species present physiological mechanisms that should vary among species in a controlled freezing event. In the course of my doctorate, this hypothesis was confirmed, finding survival to freezing temperature in the species A. gargola, B. gouveai, D. microps, H. latistriatus, H. polytaenius, M. moreirae, P. bufoninum, S. duartei and S. hayii, being a wide variety of physiological strategies to protect the animals to the low temperatures. Among the previously reported species, D. microps, H. polytaenius, P. bufoninum, S. duartei, S. hayii, were defined as freezing tolerant because they exhibit both accumulation of cryoprotectants and body ice growth during freeze exposure. On the other hand using phylogenetic analyzes, it was possible to reinforce the hypotheses that the freezing tolerance strategy is convergent throughout the evolutionary history of the amphibians, happening independently in several clades. The new findings about physiological richness at the level of adaptations to freezing in South America are only small samples of what can be found within the biodiversity existing on this continent, so the present thesis is only an incentive for future work in the area
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