Orientador: Leonardo Fernandes Fraceto / Resumo: O extenso crescimento da agricultura combinado com o uso intensivo de agrotóxicos tem causado preocupação com a manutenção dos ecossistemas e a produção de alimentos realmente saudáveis. Atualmente, têm-se buscado alternativas sustentáveis para produção agrícola como os inseticidas botânicos e nanopesticidas. Os inseticidas botânicos são extraídos de plantas e utilizados no controle de pragas, sendo estes considerados biodegradáveis, seguros e menos tóxicos para a biodiversidade. Eles podem ser encapsulados em nanocarreadores que aumentam sua estabilidade e otimizem o seu uso agrícola. Os nanopesticidas trazem benefícios para o ambiente e a produtividade agrícola, dos quais destacam-se a liberação modificada dos ingredientes ativos nos campos agrícolas, maior estabilidade do sistema, menor toxicidade aos seres vivos e redução do impacto ambiental. No entanto, percebe-se a necessidade de estudos de toxicidade dos inseticidas botânicos e dos nanopesticidas em organismos não-alvos, como abelhas e anfíbios que estão declinando rapidamente no mundo inteiro. O objetivo desse estudo foi preparar e caracterizar os sistemas carreadores do extrato de piretro e avaliar o efeito destes compostos em girinos de rã-touro (Lithobates catesbeianus) e abelhas (Apis mellifera Africanizada), utilizando biomarcadores de diferentes tipologias em nível subindividual e de indivíduo. O extrato de piretro encapsulado em nanopartículas (NLS+PIR) evidenciaram uma boa estabilidade físico-química em funçã... (Resumo completo, clicar acesso eletrônico abaixo) / Doutor

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.

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.

Orientador: Denis Otávio Vieira de Andrade / Coorientador: Carlos Arturo Navas / Banca: Ariovaldo Pereira da Cruz Neto / Banca: Célio Fernando Baptista Haddad / Banca: Fernando Ribeiro Gomes / Banca: Sidney Feitosa Gouveia / Resumo: Temperatura e disponibilidade de água são fatores que afetam importantemente a ecologia, a fisiologia e o comportamento de anfíbios. Nesse sentido, estes animais necessitam apresentar uma série de características ecofisiológicas que permita a eles lidarem potencialmente com aspectos ambientais desafiadores. Na presente tese, objetivei explorar diferentes tópicos (gradientes ecológicos, doenças e atividade) enfocando a fisiologia térmica e o balanço hídrico de anfíbios. O primeiro capítulo apresenta uma introdução geral abordando um dos temas centrais da presente tese, a fisiologia térmica de anfíbios. Entretanto, este capítulo também explora a inter-relação entre regulação da temperatura corpórea e balanço de água. O segundo capítulo investiga se parâmetros fisiológicos associados à tolerância térmica e ao balanço hídrico, em cinco espécies de anfíbios anuros, variam ao longo de gradientes altitudinais em duas cadeias montanhosas, Serra do Mar e Serra da Mantiqueira, da Floresta Atlântica. O terceiro capítulo examina os potenciais efeitos da quitridiomicose - uma doença emergente causada por fungo, considerada responsável por declínios populacionais e extinções de anfíbios em todo o mundo devido a alterações osmorregulatórias cutâneas - sobre o balanço hídrico e mortalidade de espécies de anfíbios anuros do Brasil. O quarto capítulo investiga se a atividade de dispersão diurna em juvenis do sapo Dermatonotus muelleri estaria correlacionada com parâmetros fisiológicos associados à fisiologia térmica e balanço hídrico / Abstract: Temperature and water availability are factors that affect, importantly, the ecology, physiology, and behavior of amphibians. In this sense, these animals need to present a number of ecophysiological characteristics that allows them to cope with potentially challenging environmental features. In this thesis, I aimed to explore different topics (ecological gradients, diseases, and activity) focusing on the thermal physiology and water balance of anuran amphibians. The first chapter presents a general introduction focused on one of the central themes of this thesis, the thermal physiology of amphibians. However, this chapter also explores the inter-relationship between body temperature regulation and water balance. The second chapter investigates whether or not physiological traits associated to thermal tolerances and water balance, in five anuran amphibians, vary along elevational gradients along two mountain ranges, Serra do Mar and Serra da Mantiqueira, in the Brazilian Atlantic Forest. The third chapter examines the potential effects of chytridomycosis - an emerging fungal disease claimed to cause amphibian population declines and extinctions worldwide due to cutaneous osmoregulatory disorders - on the water balance and mortality of anuran species from Brazil. The fourth chapter investigates whether or not the diurnal activity of dispersing juveniles of the burrowing frog, Dermatonotus muelleri, might be correlated with physiological traits associated to thermal physiology and water balance / Doutor

Using 2 - D NMR spectroscopy, the structure of the sex pheromone from Litoria splendida has been determined, in order to elucidate its mode of transport through the aquatic environment. The peptide was found form an α - helical structure, with a central flexible hinge region. The mode of transport through the aquatic environment has been discussed in relation to the structure. Previous work indicated that the Australian amphibian host defence skin peptides that inhibit neuronal nitric oxide synthase ( nNOS ) were likely to act indirectly on the enzyme, by binding to the co - enzyme of nNOS, calmodulin. [superscript 15] N labelled calmodulin was expressed and purified via a bacterial protein expression system and a series of 2 - D NMR [superscript 15] N - HSQC titrations was performed with Australian amphibian host defence skin peptides. in order to determine whether these peptides bind to calmodulin. The three peptides tested were found to bind, and with differing strengths of interaction. One of these was selected for further study. [superscript 15] N and [superscript 13] C doubly labelled calmodulin was then prepared in order to study the complex between this protein and the selected peptide, caerin 1.8, an Australian amphibian skin peptide isolated from Litoria chloris. A series of 3 - D NMR spectra has been recorded on this complex. The backbone atom resonances have been assigned for free calmodulin and for the calmodulin - peptide complex, using a combination of main chain directed and sequential assignment strategies. By analysing the changes in chemical shift that occur upon binding the peptide, it was determined that the mode of binding involves a stronger interaction with the C - terminal domain than the N - terminal domain. / Thesis (Ph.D.)--School of Chemistry and Physics, 2006.

Many organisms with complex life cycles undergo transition periods associated with increased vulnerability to predation. Several evolutionary adaptations have been proposed as antipredator defenses for organisms during risky transition periods. These include: shortening of the transition period, parental care, cryptic coloration, and synchrony of risky transitions with large numbers of conspecifics. The results of my research support the hypothesis that synchrony of metamorphosis and emergence from the water and aggregation during the period of transformation may be antipredator defenses for the western toad (Bufo boreas). For some anuran species, synchronous metamorphosis may function as an antipredator adaptation by swamping predators during the period of transformation. I examined the levels of synchrony of emergence from the water of metamorphosing western toads (Bufo boreas) in the presence and absence of a live snake predator, the common garter snake (Thamnophis sirtalis) in a laboratory experiment. To compare between the treatments, I measured the time to emergence from the water, the number of metamorphs emerging together, and the level of aggregation (before and during emergence) of the toads in each treatment. There was a difference between the treatments when all three factors were considered. I attributed these differences to a behavioral response in which B. boreas emerged sooner in the presence of the predator, regardless of whether individual toads had reached the point at which they were physically better suited to the terrestrial environment than the larval environment. Since the Pacific treefrog (Hyla regilla) is also preyed upon by T. sirtalis during the vulnerable period of metamorphosis, I conducted a laboratory experiment to test the effects of the presence of T. sirtalis on 1) aggregation of larval and metamorphosing H. regilla, 2) time to metamorphosis, 3) synchrony of metamorphosis, 4) time to emergence from the water and 5) synchrony of emergence from the water. The only significant effect observed in this experiment was a difference between aggregation levels of H. regilla throughout the experiment. There was, however, a strong trend in which the variances around the mean times to metamorphosis and emergence of the frogs in the control treatments were larger than those in the predator treatments. This could indicate a trend toward synchrony of metamorphosis and emergence for H. regilla in the presence of snake predators. / Graduation date: 1998

Identifying the ecological mechanisms that determine food web structure is critical for understanding the causes and consequences of diversity. The objective of this thesis was to identify the mechanisms structuring aquatic food webs across environmental gradients from a multi-level perspective (individual to ecosystem) using integrative methodology and field experiments to test classic ecological theory. My results demonstrate support for the dynamic constraints hypothesis, which predicts habitats with greater disturbance should have shorter food chains, but are not consistent with the ecosystem size hypothesis that predicts larger ecosystems have longer food chains. Insect and amphibian richness increased with increasing pond size and hydroperiod, indicating that insertion of new consumers into pond communities was driving variation in food-chain length. A multivariate analysis testing the influence of physicochemical variables on food-web characteristics revealed that hydroperiod and pond area had a strong influence on amphibian and invertebrate assemblages, trophic diversity and 15N range. Food-chain length did not respond strongly to any one variable, but instead responded weakly to multiple environmental variables, suggesting interacting influences on food-web structure. Conversely, the trophic niche of amphibian larvae was not influenced by pond hydroperiod, but did exhibit ontogenetic diet shifts. Populations of amphibian larvae with broader niche widths also had increased individual variation, supporting the niche variation hypothesis. In addition, I assessed whether species diversity influenced the magnitude of cross-habitat resource flow between aquatic and terrestrial habitats via emerging aquatic insects, metamorphosing amphibians, and litter deposition. Deposition into ponds far exceeded carbon exported via insect and amphibian emergences. We found a negative relationship between resource flux and the diversity of amphibians and insects, which contradicts the general pattern of positive biodiversity-ecosystem function relationships. My research strongly suggests environmental variation is a key process in shaping food-web structure and function and that multiple methodologies are needed to understand temporal and spatial dynamics of aquatic ecosystems.

The study of species diversity patterns and their causes remains a central theme of ecology. Work conducted over the last few decades has shown that both historical and ecological factors are important in determining species diversity patterns. Additionally, different causal mechanisms are important at different spatial and temporal scales. At the regional scale, species diversity patterns can best be studied in terms of three diversity components (alpha, beta and gamma). This study used the amphibians and reptiles of Costa Rica to examine these species diversity components at the regional scale. To accomplish this, existing species lists were compiled from the literature. Additionally, three herpetofaunal surveys were conducted at under surveyed sites to fill knowledge gaps. A survey of Parque Nacional Carara, a transitional zone site on Costa Rica’s central Pacific coast, gave evidence of a rich herpetofauna, containing species from both the dry tropical forest to the north and the wet lowland forest to the south. Survey results show that Carara’s herpetofaunal assemblage is more similar to that of the wet forest than the dry forest, and suggest many species from both assemblages reach their range limit at or near the park. Surveys of four sites in the eastern Área de Conservación Guanacaste showed rich herpetofaunal diversity and validated the newly purchased Rincón Rainforest as an important conservation area. A survey of Reserva Natural Absoluta Cabo Blanco provided a preliminary list of amphibian and reptile species of the lower Nicoya Peninsula and highlighted the importance of Laguna Balsitas to the local amphibian fauna. A comparison of amphibian and reptile alpha diversity among 17 sites throughout Costa Rica showed highest alpha amphibian diversity in the lowland rainforests of the Pacific versant and highest reptile alpha diversity in lowland rainforests of the Atlantic versant. An analysis of beta diversity produced dendrograms showing sites within lowland ecoregions being most similar. A Canonical Correspondence Analysis (CCA) of environmental variables showed two climate gradients, an elevation/temperature gradient and a sun/rain gradient, to be important in determining species diversity patterns for both amphibians and reptiles in Costa Rica.

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<p>Rapid urbanization threatens the survival of native wildlife species worldwide. In order to fully grasp the implications of the ongoing growth of urban areas on biodiversity, conservationists need to be able to quantify the response patterns of a wide range of different species to the expansion of urban and suburban land use. In this study, we set up two road-based transects across gradients of urbanization and habitat loss in the diverse longleaf pine forests of the Sandhills region of North Carolina, USA. With funding provided by the NC Wildlife Resources Commission, we drove the transects repeatedly at night in the field seasons of 2006-2008, tallying all vertebrate animals encountered (live or dead). The first transect (driven in all three years; 75 km long) ran from the urban areas of Southern Pines and Pinehurst down to the remote and relatively pristine habitats associated with the state-owned Sandhills Gamelands. The second transect (driven in 2007 and partially in 2008; 69 km long) began at the terminus of the first transect in the Gamelands, and then stretched down to the urban zones of Hamlet and Rockingham. </p><p> A total of 4900 vertebrate animals representing 69 species were observed on or near the road routes after driving a total of 16,625 km. This total includes 592 nightjars (ground-nesting nocturnal birds; e.g. whip-poor-wills) that we heard while driving the transects. In addition, in 2007 we surveyed for the nightjars and for quail (a high-priority game species that also nests on the ground) using 75 point count locations evenly distributed along the northern road route. </p><p> Regression tree analysis (a robust, nonparametric technique with minimal assumptions) was used to model the animal observation rates for a given 1 km road segment or point count as a function of various habitat variables measured within corresponding buffer zones for each segment. We also modeled snake and bird encounter rates as a function of mesopredator mammal observations. </p><p> Our results reveal that amphibian, snake, and ground-nesting bird observation rates are negatively associated with increasing levels of traffic and impervious surface. Conversely, mesopredator mammals (and domestic cats in particular) responded slightly positively to increasing urbanization, and negatively to protected area coverage. Both ground-nesting birds and snakes showed signs of negative correlations with mesopredator encounter rates, although these trends were not always significant due to high variability in the mesopredator data. </p><p> In order to try and confirm the results of the regression tree analyses, we also used a multivariate ordination approach (non-metric multidimensional scaling) to visualize the integrated community structure of all of the major vertebrate groups we observed in the Sandhills. The ordinations revealed that while the snake, ground-nesting bird, and amphibian groups were similar to each other in terms of their avoidance of urban conditions, the cats and native mesopredator species actually seemed to define widely divergent axes of community variation. Cats in particular were separated from the other groups on 2 out of 3 axes of the species-space ordination. Still, as we noted above for the regression tree models, it is difficult to sort out with our correlative data set whether cats and other mesopredators truly played an independent role in structuring and/or depleting the other wildlife guilds along our route. More experimental approaches are recommended for trying to resolve whether overabundant predators or road mortality and inappropriate habitat are more to blame for the much reduced encounter rates we observed for the snakes, birds, and amphibians in urban areas. Future studies will also be needed to confirm the logical assumption that road encounter rates provide a reasonably accurate index of the relative abundance of the different animal groups along the survey routes.</p> / Dissertation