Populações de muitas espécies de anfíbios apresentaram um severo declínio global nas últimas décadas, o qual vem sendo documentado em diversas regiões geográficas. Muitos fatores parecem associados ao declínio dos anfíbios, dentre os quais as mudanças climáticas representariam uma das maiores ameaças à permanência dessa linhagem no planeta em razão da sensibilidade desses animais a taxas aceleradas de alteração no clima. O aumento da incidência de radiação ultravioleta-B (UVB) na superfície da Terra pode induzir diversos impactos negativos nos anfíbios como diminuição do crescimento, aumento de efeitos genotóxicos, redução do desempenho locomotor e elevação nas taxas de mortalidade. Os impactos causados pelo UVB podem ainda ser amplificados pela temperatura ambiental, uma vez que em baixas temperaturas o metabolismo é reduzido, afetando o crescimento, o desempenho locomotor e a atividade de enzimas de reparo dos danos causados no DNA pelo UVB. A presente dissertação investigou os efeitos conjuntos da ação do UVB e da temperatura durante o desenvolvimento de girinos em Anura. Os resultados demostraram que girinos expostos ao UVB em temperatura elevada apresentaram um fenótipo com maior probabilidade de sobrevivência em ambientes naturais, o que contrasta com as predições negativas dos efeitos da redução da camada de ozônio e do aquecimento global. Em contraste, a exposição ao UVB induz elevadas quantidades de dano no DNA em girinos, independente da temperatura de manutenção. Adicionalmente, girinos expostos ao UVB em baixa temperatura apresentaram desempenho locomotor reduzido, alta mortalidade, e possivelmente baixa eficiência de reparo de DNA. Em síntese, a presente dissertação congrega resultados que permitem identificar um efeito sinergético entre a exposição ao UVB e temperatura ambiental. / Populations of several amphibian species experienced a severe global decline in the past decades, which has been documented in diverse geographic regions. Several factors seem associated with amphibians decline, among them climate change may represent a major threat due to the sensibility of these animals to accelerated rates of environmental change. The increased incidence of ultraviolet-B radiation (UVB) on the Earth\'s surface may trigger several negative impacts on amphibians, including reduced growth, increased genotoxic effects, limited locomotor performance and increased mortality rates. Such UVB effects may be influenced by environmental temperature, because in the cold the metabolism is reduced, affecting growth, locomotor performance, and activity of enzymes that repair DNA damage induced by UVB. The present study investigated likely interactions between effects of UVB exposure and temperature during the development of anuran tadpoles. Results showed that exposing tadpoles to UVB at high temperatures resulted in phenotypes with increased survival probability in natural environments, which contrasts with predictions of negative consequences imposed by the depletion in the ozone layer and the global warming. Furthermore, tadpoles exposed to UVB at low temperature exhibited reduced locomotor performance, increased mortality rates, and possibly lower efficiency of DNA repair. In conclusion, this dissertation comprises results that sustain existence of synergistic effects between UVB exposure and environmental temperature.

Made available in DSpace on 2014-06-11T19:22:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-07-12Bitstream added on 2014-06-13T20:09:25Z : No. of bitstreams: 1 borges_ff_me_jabo.pdf: 2088766 bytes, checksum: 5403ba70f285528d3490e9444e9af9fd (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / O estudo foi realizado no Setor de Ranicultura do Centro de Aquicultura da Universidade Estadual Paulista, Câmpus Jaboticabal/SP em dois períodos distintos, compreendendo uma fase de girinagem e uma fase de engorda no ciclo de criação de rã-touro. Os objetivos foram verificar as características físicas, químicas e microbiológicas da água de entrada e de saída dos tanques em cada fase do ciclo. Os resultados obtidos foram comparados com a legislação ambiental CONAMA 357 de 2005, para verificar se o manejo utilizado em cada fase causa alterações na qualidade da água. Foram analisadas as variáveis temperatura, pH, oxigênio dissolvido, condutividade elétrica, turbidez, nitrogênio amoniacal, nitrato, fósforo total, DBO5, DQO e Escherichia coli em cada etapa do ciclo. O delineamento experimental foi o Inteiramente Casualizado, com dois tratamentos, água de abastecimento e efluente e seis repetições (tanques) em um esquema de parcelas subdivididas, sendo as sub-parcelas as coletas no tempo. As coletas das amostras foram realizadas a cada quinze dias no período da manhã. Na fase de girino o experimento foi realizado entre novembro de 2008 e janeiro de 2009 e teve duração de 76 dias, até os animais completarem a metamorfose. Não foi observada diferença significativa (p>0,05) entre os tratamentos para temperatura, condutividade, turbidez, DQO e E. coli. Entretanto, esses parâmetros variaram nas diferentes coletas. As variáveis pH, oxigênio dissolvido, fósforo total, amônia, nitrato e DBO5 tiveram diferença significativa (p<0,05) entre os tratamentos. Porém, somente as concentrações de fósforo total e DBO5 encontraram-se acima da recomendada pela legislação. A fase de recria teve duração de 77 dias, compreendendo o período de novembro de 2009 a janeiro de 2010, até os animais atingirem o peso de abate. Todas as análises apresentaram diferença significativa... / The study was performed at the frog culture Sector, Aquaculture Center, Sao Paulo State University, Campus Jaboticabal, SP in two different periods, including a tadpole and growout phase in the cycle of creation of the bullfrog. The objectives were to verify the physical, chemical and microbiological water inlet and outlet of the tanks at each stage of the cycle. The results were compared with environmental legislation CONAMA 357, by 2005, to verify whether management used at each stage cause changes in water quality. The variables temperature, pH, dissolved oxygen, electrical conductivity, turbidity, ammonia nitrogen, nitrate, total phosphorus, BOD5, COD and E. coli at each stage of the cycle. The experimental design was completely random, with two treatments, water supply and sewage and six repetitions (tanks) in a split plot, and the sub-plots samples collected over time. The collections of samples were taken fortnightly during the morning. At tadpole phase, the experiment was conducted between November 2008 and January 2009 and lasted 76 days until the animals complete metamorphosis. There was no significant difference (p> 0.05) among treatments for temperature, conductivity, turbidity, COD and E. coli. However, these parameters varied in different samples. The pH, dissolved oxygen, total phosphorus, ammonia, nitrate and BOD5 were significantly different (p<0.05) among treatments. But, only the concentrations of total phosphorus and BOD5 were found above the recommended legislation. The growing phase lasted 77 days, including the period November 2009 to January 2010, until the animals reach slaughter weight. All analysis showed significant differences (p<0.05) among treatments and between collections. The variables, dissolved oxygen, total phosphorus, ammonia, BOD5 and E. coli had their values above those permitted by law... (Complete abstract click electronic access below)

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-19T18:11:03Z No. of bitstreams: 1 DanielBritoOliveira.pdf: 1113712 bytes, checksum: 1f754d1e3daa67a9a1459e26284f82ca (MD5) / Made available in DSpace on 2017-06-19T18:11:03Z (GMT). No. of bitstreams: 1 DanielBritoOliveira.pdf: 1113712 bytes, checksum: 1f754d1e3daa67a9a1459e26284f82ca (MD5) Previous issue date: 2010-07-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) / Urbanization brings many consequences such as fragmentation and degradation of the remaining forest fragments. Degradation in these fragments can negatively affect the forest species, but favor their use by open area species. Thus we aimed to investigate if tadpoles of open area species are developing, together with those of forest species, in water bodies located in forest fragments in Sao Luis Island, MA, Brazil. For this we collected tadpoles in 32 pools with varied characteristics divided into three different types of environment (open area, outer edge of the forest, and forest interior), during the years 2008 and 2009. We recorded 20 species in five families (Bufonidae, Hylidae, Leptodactylidae, Leiuperidae, Microhylidae). The environmental variables accounted for much of the variation in the abundance of tadpoles, and the percentage of vegetation in the pool, the vegetation height in the forest edge, the distance to the forest, and the depth of the pool showed significative effects. Tadpoles of open area species occured in water bodies located in the forest interior. The increased presence of generalist species, and the reproductive success of open area species in the forests indicate that these areas are impacted. / A urbanização traz diversas conseqüências como a fragmentação e a degradação dos remanescentes florestais. A degradação nesses fragmentos pode afetar negativamente as espécies de mata, mas favorecer a sua utilização por espécies de áreas abertas. Assim, objetivamos investigar se girinos de espécies de áreas abertas estão se desenvolvendo, junto com os de espécies de mata, nos corpos d’água localizados em fragmentos de mata na ilha de São Luis, MA, Brasil. Para isso coletamos girinos em 32 poças de características variadas distribuídas em três tipos de ambiente (área aberta, borda externa de mata e interior de mata), durante os anos de 2008 e 2009. Registramos 20 espécies distribuídas em 5 famílias (Bufonidae, Hylidae, Leptodactylidae, Leiuperidae, Microhylidae). As variáveis ambientais que responderam por grande parte da variação nas abundâncias de girinos foram: porcentagem de vegetação no corpo d’água, a altura da vegetação na borda da mata, a distancia para a mata e a profundidade do corpo d’água. Os girinos de espécies de área aberta ocorreram nos corpos d’água localizados na mata. Além disso a maior presença de espécies generalistas e o sucesso reprodutivo das espécies de área aberta no interior das matas indicaram que estas áreas estão impactadas.

Tadpoles represent a key element in evolutionary history and the diversification of anurans. Through a two-phase life cycle, anurans can take advantage of the available resources in terrestrial and aquatic environments. Several studies have demonstrated that larval morphology may represent an important source of evidence for evolutionary studies. However, tadpoles are often ignored and little is known about their anatomy and biology. An example of this problem is the superfamily Dendrobatoidea, for which there is almost no information on tadpoles. This study aims to fill this gap. I performed a cladistic analysis of the superfamily Dendrobatoidae with emphasis on larval characters. The final dataset also included adult phenotypic characters and DNA sequences. The final matrix was composed of 621 terminals and more than 500 phenotypic characters of which 392 were individualized from larval systems, such as chondrocranium, cranial musculature and buccopharungeal anatomy. In my optimum hypothesis I recovered Dendrobatoidea as well as all its subfamilies and genera as monophyletic. Larval characters optimized as synapomorphies at different levels. Based on the topology and distribution of the characters, I discuss the evolution of several lifestyles and morphologies, such as oophagy, endotrophy, and carnivory in Dendrobatoidea / Girinos representam um elemento chave na história evolutiva e na diversificação dos anuros. Através de um ciclo de vida bifásico, os anuros conseguem aproveitar os recursos disponíveis tanto no ambiente terrestre como no aquático. Vários estudos demonstraram que a morfologia larvar pode representar uma importante fonte de evidências para estudos evolutivos. No entanto, girinos frequentemente são ignorados e pouco se sabe sobre sua anatomia e biologia. Um exemplo dessa problemática é a superfamília Dendrobatoidea, para a qual quase não há informações sobre seus girinos. O presente estudo visa contribuir para o preenchimento dessa lacuna. Eu realizei uma análise cladística da superfamília Dendrobatoidae, tendo como foco caracteres larvais. O dataset final também incluiu caracteres de adulto e sequências de DNA. A matriz final foi composta por 621 terminais e mais de 500 caracteres fenotípicos, dos quais 392 foram individualizados de sistemas larvais como condrocrânio, musculatura craniana e cavidade buccopharingeal. Em minha hipótese ótima, eu recuperei Dendrobatoidea bem como todas suas subfamílias e gêneros monofiléticos. Caracteres larvais otimizaram como sinapomorfias em diferentes níveis. Mediante a topologia e a distribuição dos caracteres, eu discuto a evolução de uma série de modos de vida e morfologias, como a oofagia, o endotrofismo e a carnivoria em Dendrobatoidea

A variety of aquatic habitats with different levels of potential predators are available to larval amphibians in Central Amazon rainforest. The anuran community at Reserva Florestal Adolfo Ducke, 25 km east of Manaus, Amazonas, Brasil, was studied to determine which species have eggs and/or larvae in water and how those larvae are distributed in time and space. The temporal and spatial distribution of potential predators as well as abiotic characteristics of these waterbodies were determined simultaneously to test for correlations with the distribution of tadpoles. The distribution of tadpoles was strongly related to fish predation pressure. Several tadpole species were found only in waterbodies with high fish abundance and thus have the ability to survive with fish. Most of these tadpoles were found to be unpalatable in controlled experiments. Unpalatability is the major adaptation allowing the coexistence of tadpoles and fish and is thus a major factor affecting tadpole community composition in this system. Controlled experiments showed that fish do not eat anuran eggs while the tadpoles of Leptodacrylus knudseni and Osteocephalus taurinus ate all types of eggs offered. The percentage of anurans with aquatic oviposition was positively related to fish abundance and negatively related to the occurrence of species of tadpole that ate eggs in experiments. These findings suggest that the present patterns of anuran distribution represent an evolutionary response to predation on the eggs and larvae. Contrary to the models of Heyer et al. (1975) and Wilbur (1984), desiccation and predation-pressure were not the major factors affecting species richness within waterbodies of the RFAD rainforest. In support of the model of Heyer et al. (1975), anuran species richness was correlated with the size of the waterbody. This could be because the size of the waterbody is related to increased complexity and availability of microhabitats. The range of volumes of waterbodies was also found to directly affect species richness of the RFAD community. While predation appeared to have a limited effect on species richness of individual ponds, predation-pressure was found to have a major influence on species composition. Anuran eggs and larvae survived with specific predators by possessing particular survival-traits (e.g. unpalatability and oviposition strategies). However, survival-traits were not effective against all predators in all habitats. The distribution of different predators among ponds provides a patchy environment on a local scale (i.e. within ponds). When combined with the variety of survival-traits exhibited by the anuran species, this spatial patchiness in predation contributes towards species richness within the anuran community of the RFAD rainforest.

The documented decline of amphibian populations over the past two decades has increased attention towards amphibian conservation. Much of this attention has been focused on testing hypotheses as to the causal factors of these declines, however providing convincing data to support any of these hypotheses has proved difficult. The testing of these hypotheses and the implementation of endangered species recovery programs has been restricted by a lack of knowledge of the ecology and population demography of amphibian species that have suffered dramatic declines. This thesis presents aspects of the research phase of the recovery program for the Southern Corroboree Frog, Pseudophryne corroboree, a species that declined to very low numbers during the early 1980's. In particular, this research aimed to determine the distribution, abundance, population dynamics and demography of this rare species. A complete reassessment of the conservation status of P. corroboree was undertaken and the nature of the persistence of this species across the landscape was analysed. Temporal trends in abundance and its relationship with population size were also investigated. Early life-history survivorship and recruitment to metamorphosis were studied at the scale of individual nest sites and populations, and the adult male population age structure and annual mortality were investigated using skeletochronology. The shout/response survey technique was used to survey and monitor the number of breeding male P. corroboree during this study. This method was found to provide consistent results when the surveys were conducted over a short (two week) period during the peak breeding season in January. Neither time of day, nor the number of males present at a pool, was found to influence the level of responsiveness of male P. corroboree to the shout/response technique. Variation in the number of responding males to the shout/response technique through the breeding season, assessed at a single site over two seasons, was unimodal with the peak responding period occurring during the last two weeks of January during both the 1998 and the 1999 breeding seasons. A systematic survey covering 213 sites across the entire historic distribution of P. corroboree found this species to be persisting at 79 sites. The majority of these sites were in the northwestern portion of the species former range, around the Jagungal Wilderness area, while no extant sites were found in the south-eastern portion of the species former range in the Smiggin Holes and Perisher Blue ski resorts area. The overall abundance of males at persistent sites was extremely low, with 92 percent of sites having fewer than ten responding males. Only one site was found to support greater than fifty responding males. A logistic regression analysis found the persistence of P. corroboree to be associated with increased number of pools within a site, decreased distance to nearest extant population and geographic position (latitude and longitude) in the landscape. While annual variation was observed in the number of breeding males for individual sites, there was no overall trend for an increase or decrease in the number of males, regardless of population size. The average annual extinction rate for local populations was five percent during this study, with those populations becoming extinct having very few breeding males (between one and three) during the previous season. Embryonic and tadpole survivorship was monitored for individual nests at three sites across three years. Recruitment to metamorphosis for P. corroboree was characterised by high variation in survivorship between nest sites, populations and years, while overall recruitment for nest sites was skewed towards lower survivorship. Average nest survivorship to metamorphosis across all sites and years was ten percent but the skewed nature of this survivorship meant that the majority of nest sites attained very low or no survivorship. The low proportion of nest sites that did attain high survivorship provided the greatest contribution to overall recruitment. The levels of embryonic and tadpole mortality observed in this study would be providing a considerable contribution to the regulation of current population sizes. The greatest level of early life-history mortality was observed during the late autumn/winter egg and tadpole stage, with high survivorship during the summer and early autumn egg stage and the post-winter tadpole stage. The estimated sex ratio for seven populations, based on the number of eggs within male nest sites, indicated that for most populations, regardless of population size, there was a greater proportion of females to males. In general, the estimated sex ratio of smaller populations showed greater annual variation and had a lower average number of females to males than the single large population. Tadpole surveys conducted across remnant populations during both 1998 and 1999 found recruitment to metamorphosis to be very low for the majority of populations. A third of all populations during both years attained no recruitment to metamorphosis, with those populations that did attain recruitment typically having fewer than 20 tadpoles. While sites with more frogs generally recruited more tadpoles, there was no strong relationship between population size and the number of tadpoles recruited per male at the scale of either pool or site. There was also no significant difference in recruitment levels between the two years. Tadpole surveys across breeding pools within the single large population also found very low tadpole abundance. There was no strong relationship between the number of male frogs at a pool and the number of tadpoles per male and there was no significant difference in tadpole abundance between the two years. Based on the low density of males at pools and sites (typically less than five), and the skewed nature of nest survivorship identified from monitoring individual nest sites, it seems likely that both deterministic and stochastic factors are influencing recruitment levels in remnant populations of P. corroboree. This study determined that adult male P. corroboree could be accurately aged using the technique of skeletochronology, and this technique was used to determine the adult male population age structure for three populations. The results indicated that adult male P. corroboree can reach sexual maturity from metamorphosis in three years, but the majority of individuals take four years. The oldest individual identified in this study was nine years old from metamorphosis. The adult male age structure at the single large site showed very little annual variation, whereas the two smaller populations showed highly pulsed age structures from one year to the next. The size of adult males was found to be a poor predictor of age. Annual adult male survivorship, calculated by following cohorts from one year to the next, was 55 percent. Based on this calculation of annual adult male survivorship, it seems likely that the initial decline in P. corroboree involved increased levels of adult mortality. The results of this study indicate that the persistence of. corroboree in the wild is precarious in the short-term. For this reason, it is recommended that efforts be undertaken to secure this species ex situ. Attempts to increase population numbers in the wild would greatly benefit from determining the factor(s) that have caused the decline in this species, however, failure to do so should not preclude field experimental management aimed at developing technique to increase the size of remnant populations. This is because it is likely that small population stochasticity is contributing to the current regulation of population size and it is possible that the factors that caused the decline in this species cannot be removed from the environment.

Tadpoles are known to behaviorally respond to visual, auditory or chemical cues. I examined the influence of group size and light conditions on the activity of Phyllobates vittatus. I performed laboratory experiments to measure locomotor activity. Activity levels of tadpoles were higher in the groups. Light conditions did not influence activity level of tadpoles. My results suggest that the group size is one of the main factors influencing tadpole locomotor activity of Phyllobates vittatus.

My thesis has accomplished 3 significant contributions to neuroscience. Firstly, I have discovered a novel example of vertebrate deep-brain photoreception. Spontaneously generated fictive locomotion from the isolated nervous system of pro-metamorphic Xenopus tadpoles is sensitive to the ambient light conditions, despite input from the classical photoreceptive tissues of the retina and pineal complex being absent. The photosensitivity is found to be tuned to short wavelength UV light and is localised to a small region of the caudal diencephalon. Within this region, I have discovered a population of neurons immuno-positive for a UV-specific opsin protein, suggesting they are the means of phototransduction. This may be a hitherto overlooked mechanism linking environmental luminance to motor behaviour. Secondly, I have advanced the collective knowledge of how both nitric oxide and dopamine contribute to neuromodulation within motor control systems. Nitric oxide is shown to have an excitatory effect on the occurrence of spontaneous locomotor activity, representing a switch in its role from earlier in Xenopus development. Moreover, this excitatory effect is found to be mediated in the brainstem despite nitric oxide being shown to depolarise spinal neurons. Thirdly, I have developed a new preparation for patch-clamp recording in pro-metamorphic Xenopus tadpoles. My data suggest there are several changes to the cellular properties of neurons in the older animals compared with the embryonic tadpole; there appears to be an addition of Ih and K[sub](Ca) channels and the presence of tonically active and intrinsically rhythmogenic neurons. In addition, I have shown that at low doses dopamine acts via D2-like to hyperpolarise the membrane potential of spinal neurons, while at higher doses dopamine depolarises spinal neurons. These initial data corroborate previously reported evidence that dopamine has opposing effects on motor output via differential activation of dopamine receptor subtypes in Xenopus tadpoles.

The increasing level of the UV-B irradiation due to depleting of the ozone layer is considered to be one of the causes of global amphibian declines. The UV-B radiation causes damage to the DNA in the nuclei of the skin cells and their eventual death. In many amphibian species there was found a negative influence of the UV-B radiation on the hatching success of tadpoles and their subsequent viability. It has been assumed that tadpoles are able to actively avoid places with the higher exposure of the UV-B radiation thanks to their locomotion. In this experiment tadpoles could have chosen between a zone with the UV radiation (UV-B and UV-A) and without the UV radiation. The tadpoles have not been exposed to the UV radiation before the measurement started. The location of the tadpoles during the measurement was recorded by CCD camera. A computer program EthoVision then evaluated the time that these tadpoles spent in each of the zones and the total path length these tadpoles has swum in the zones. The measurements were performed for two groups of tadpoles differing in age to determine whether the level of development may affect the tadpoles' preference to the UV radiation. The tadpoles in both groups spent more time in the zone without the UV radiation. The tadpoles in the more advanced development phase have spent 7 times more time in average in the zone without the UV radiation than in the zone with it. The tadpoles from the second group have spent in average 2.5 times more time in the zone without the UV radiation than in the zone with the UV radiation. The total swimming path length of advanced tadpoles was almost 2.5 times longer in the zone without the UV radiation than in the zone with the UV radiation. Conversely, the total path length of younger tadpoles did not significantly differ between the zones. The total time spent in the zones with / without the UV radiation did not differ between the groups of tadpoles. Also the total path length did not differ between the groups in the zone with the UV-B radiation. However, the total path length of tadpoles had differed between groups in the zone without the UV radiation.

A estrutura de comunidades em poças tem sido explicada por competição de recursos, predação e permanência da água. No presente estudo, eu avaliei o efeito do gradiente predação-hidroperíodo sobre a riqueza de espécies e composição de guildas de girinos em poças, e também a co-ocorrência das espécies, testando a existência de padrões segregados que podem ser atribuídos as interações competitivas. O estudo foi realizado no município de Caçapava do Sul, Rio Grande do Sul, sul do Brasil. Eu amostrei girinos e predadores invertebrados em 38 poças, com diferentes tamanhos e graus de permanência. As coletas foram realizadas em duas estações: na primavera de 2007 (novembro) e no verão de 2008 (janeiro). Eu medi a área e a profundidade das poças em cada evento de coleta e registrei a riqueza da vegetação aquática e das margens, assim como a abundância e riqueza de predadores. Eu classifiquei as espécies em guildas baseadas em oito características eco-morfológicas. As espécies foram agrupadas através de ligação completa, usando o coeficiente de Gower. Eu analisei a relação da riqueza de girinos com as variáveis ambientais através de regressão múltipla, e usei Análise de Correspondência Canônica para relacionar a composição das guildas com os descritores ambientais. A co-ocorrência dos girinos foi analisada através de três algoritmos de modelo nulo: linhas e colunas fixas, linhas fixas e colunas proporcionais descartando-se matrizes degeneradas, linhas fixas e colunas proporcionais incluindo matrizes degeneradas. Nove matrizes de presença ausência foram testadas: ocorrências totais (primavera e verão) do conjunto total de espécies, e distinguindo as espécies em duas guildas (bentônicos e nectônicos), e ocorrências de primavera e verão para o conjunto total e as duas guildas. Das 38 poças com água na primavera, somente 22 permaneceram com água na amostragem de verão. Ao todo 10852 indivíduos de 21 espécies foram coletados. As espécies foram classificadas em sete guildas: suspensor-raspador (Sr), nectônicos (N), suspensor-filtrador (Sf), bentônicos com ninho de espuma, com e sem agregação (BI e BII), e bentônicos sem ninho de espuma com olhos dorsais ou laterais (BIII e BIV). A riqueza de espécies cresceu com a abundância de predadores, que foi a única variável explanatória relacionada a mesma. A composição das guildas foi explicada pela abundância de predadores e a profundidade média registrada na primavera. A co-ocorrência dos girinos mostrou padrões segregados para 14 dos 25 modelos testados. A maioria dos modelos com matrizes degeneradas rejeitou a hipótese nula. Os modelos com linhas e colunas fixas, e com as linhas fixas, colunas proporcionais e sem matrizes degeneradas mostraram muitos resultados similares. A segregação também foi influenciada pela combinação de espécies e estação consideradas. Em geral, para o conjunto total de espécies a coocorrência foi aleatória, para os bentônicos foi segregada para as ocorrências totais e de primavera, para os nectônicos apenas no verão. Os resultados das análises de gradiente e co-ocorrência sugerem que girinos são regulados pelos predadores que filtram a composição das guildas e podem reduzir a competição. Para girinos bentônicos, que ocupam poças com baixa abundância de predadores, competição pode ser um fator de estruturação importante. / The community structure of pond systems has been shown to be affected by resource competition, predation and permanency. Here, I evaluated the effect of the permanency-predation gradient in ponds on species richness and guild composition of tadpoles, and accessed the co-occurrence, searching segregated patterns that could be attributed to competitive interactions. The study was carried out Caçapava do Sul, Rio Grande do Sul state, southern Brazil. I sampled tadpoles and invertebrate predators in 38 ponds, with distinct sizes and permanency degrees. The collections were carried out twice: in spring 2007 (November) and summer, 2008 (January). I measured area and depth at each pond in each collection event, and recorded richness of aquatic and bank vegetation, and abundance and richness of predators. I conducted a guild classification of the species pool based on eight variables related to morphological and ecological features. Species were grouped through complete linkage agglomerative clustering method, using Gower coefficient. I evaluated the relation of tadpole richness with environmental variables using multiple regression, and Canonical Correspondence Analysis for guild composition. The tadpole co-occurrence was analyzed through three null models algorithm: fixed rows and columns; fixed rows, proportional columns, discharging degenerate matrices; and fixed rows, proportional columns, including degenerate matrices. Nine presence/absence matrices were tested: total occurrences (spring and summer) of the complete species pool, and distinguishing species of two tadpole guild (benthonic and nektonic), and spring and summer occurrence of total species pool and two guilds. Of the 38 ponds with water in the spring sampling, only 22 remained with water in the following summer sampling. A total of 10,852 individuals and 21 species of tadpoles were collected in the two sampling events. The species were classified into seven guilds: suspension-rasper (Sr), nektonics (N), suspension-feeder (Sf), benthonics with foam nests with and without school behavior (BI and BII), and benthonics without foam nests with lateral and dorsal eyes (BIII and BIV). Species richness increased with abundance of predators, which was the only explanatory variable related to it. Guild composition was explained by abundance of predators and mean depth recorded in spring, which was correlated with maximal depth. The tadpole co-occurrence showed a segregated pattern for 14 of the 25 tested models. Most models with degenerate matrices rejected the null hypothesis. The models with row and columns fixed, and row fixed, column proportional without degenerate matrices showed more similar results. Segregation was also influenced by the combination of species dataset and the season considered. In general, for the total species pool the co-occurrence was random, for benthonic species was segregated for the total and spring occurrences, and for nektonic in summer. The results of gradient and co-occurrence analysis suggest that tadpoles are regulated by predators that filter guild composition and could reduce competition. For benthonic species, which inhabit ponds with lower abundance of predators, competition can be a major structuring constraint.