Cardiovascular disease is a major cause of morbidity and mortality around the globe, which is linked to athero-thrombosis. The risk factors for atherothrombosis, thus cardiovascular disease is impaired anti-thrombotic and antiinflammatory functions of the endothelium. Thrombosis is a hallmark of cardiovascular disease/complications characterised by increased platelet activation and increased secretion of platelet micro-particles that induce angiogenesis. This study determined the role of platelet micro-particles derived microRNA in the regulation of angiogenesis and migration, with a focus on the regulation of thrombospondin-1 release by platelet micro-particles delivered Let- 7a. The role of thrombospondin-1 receptors (integrin beta-1 and integrin associated protein) and downstream caspase-3 activation were explored by Let-7a inhibition prior to PMP treatment. MicroRNA dependent modulation of proangiogenic proteins including monocyte chemoattractant protein-1 and placental growth factor, and recruitment of activating transcription factor-4 protein to their promoter regions were explored. Main findings are: 1. Platelet micro-particles induce angiogenesis, migration, and release of novel cytokine subsets specific to platelet micro-particle’s RNA content. 2. The targeting of thrombospondin-1 mRNA by platelet micro-particles’ transferred Let-7a chiefly modulate the angiogenic effect on endothelial cells. 3. The inhibition of thrombospondin-1 translation enable platelet micro-particles to increase angiogenesis and migration in the presence of functional integrin beta-1 and integrin associated protein, and reduced cleaving of caspase-3. 4. Platelet micro-particle modulate the transcription of monocyte chemoattractant protein-1 and placental growth factor in a Let-7a dependent manner. 5. Let-7a induce angiogenesis ii independent of other platelet micro-particle’s microRNAs. Platelet micro-particle derived Let-7a is a master regulator of endothelial cell function in this model, which presents an opportunity for the development of new biomarkers and therapeutic approaches in the management of cardiovascular disease. Future studies should aim to confirm these findings in-vivo.

Schätzungen über die Gesamtzahl der Vergiftungen in Deutschland belaufen sich auf 150 - 200.000 pro Jahr. In Deutschland machen Vergiftungsfälle 10% der in Notaufnahmen und auf Intensivstationen behandelten Patienten aus. Bis dato gibt es in Deutschland nur wenige strukturiert erfasste epidemiologische Daten von vergiftungsbedingten Todesfällen. In der vorliegenden Arbeit wurden die vergiftungsbedingten Todesfälle aus dem Giftinformationszentrum-Nord (GIZ-Nord) für den Zeitraum vom 01.01.1996 bis einschließlich 31.12.2009 retrospektiv analysiert. Insbesondere vor dem Hintergrund der Toxikovigilanz konnten folgende Fragen zu Risikokonstellationen für letale Vergiftungen durch diese Arbeit beantwortet werden: 1. Gibt es bei den vergiftungsbedingten Todesfällen jahreszeitliche Schwankungen? Ja, die vergiftungsbedingten bzw. suizidalen letalen Intoxikationen zeigen jahreszeitliche Schwankungen mit einem maximalen Anteil im Frühling von knapp 30% und dem geringsten Anteil im Herbst mit etwa 20%. 2. Bergen die iatrogen bedingten Vergiftungen ein besonderes Mortalitätsrisiko? Ja, die iatrogenen Vergiftungen weisen die höchste Mortalitätsrate mit knapp 5 ‰ aller iatrogenen Expositionen auf, vor allem bei parenteraler Arzneimittelapplikation. 3. Stellen Adoleszente (Heranwachsende und Jugendliche) und Senioren über 70 Jahre besonders gefährdete Altersgruppen für letale Intoxikationen dar? Ja, beide Populationen stellen besondere Risikogruppen für vergiftungsbedingte Todesfälle dar. Vor allem männliche Heranwachsende repräsentieren eine Risikogruppe für letale Intoxikationen durch Abusus. 30% aller vergiftungbedingten Todesfälle durch Abusus sind bei männlichen Jugendlichen aufgetreten. Senioren (Männer und Frauen) über 70 Jahre sind eine im hohen Maß gefährdete Altersgruppe für letale Vergiftungen. Einerseits ist die relative Mortalitätsrate bezogen auf alle Expositionen dieser Altersgruppe mit knapp 6 ‰ am höchsten. Andererseits zeigen die suizidalen Intoxikationen bei den Senioren eine zunehmende Tendenz. Außerdem bilden Senioren mit einem Anteil von 24% die Gruppe mit dem größten Anteil an den letalen nicht suizidalen Intoxikationen. Mehr als 70% der akzidentellen letalen Intoxikationen und 50% der letalen Vergiftungen durch Verwechslungen betreffen Senioren, dabei sind Frauen mehr als 3fach häufiger betroffen als Männer. Darüber hinaus sind Senioren durch Aspiration schäumender, prinzipiell niedrig toxischer Kosmetika und tensidhaltiger Chemikalien besonders gefährdet. 4. Gibt es bei den gewerblichen Expositionen besondere Risikokonstellationen? Ja, die gewerblichen Expositionen, die mit einer hohen Männerlastigkeit auftreten, bergen eine hohe letale Intoxikationsgefahr. Vor allem bei den gewerblichen inhalativen Expositionen von toxischen Reizgasen besteht eine Gefährdung für die betroffenen Beschäftigten, aber auch für die nicht selbstgeschützten Ersthelfer: 6% der inhalativen gewerblichen Intoxikationen durch Schwefelwasserstoff endeten letal.

Biological invasion has become a major threat to economy, ecology, global biodiversity and ecosystem function of aquatic ecosystems. The main aim of the thesis was to study the effects of the zebra mussel (Dreissena polymorpha), a versatile invasive species, on phytoplankton dynamics and ecosystem function of lakes. In a first attempt, I compared the density of Dreissena and the physicochemical data of ecosystems that it invaded among North American and European lakes to identify important factors in its invasion success. Secondly, I investigated the impact of zebra mussels on phytoplankton community composition in a natural lake. Thirdly, I evaluated whether zebra mussel feeding behavior were affected by the presence of predatory waterborne cues. Finally, I examined the effect of Dreissena on seston stoichiometry. A Generalized Additive Model revealed that a joint effect of surface area, mean depth, total phosphorus and calcium concentrations can explain the variability in Dreissena density. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics. Risk cues released by predators affected both feeding rate and prey selection of the mussels and had cascading indirect effects on phytoplankton biomass and community structure. I found that the flux in nutrients caused by differences in zebra mussel consumption lead to a variation in phytoplankton nutrient limitation. The flexibility of zebra mussel feeding behavior and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences. The results of this thesis contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. The results suggested that zebra mussel can indirectly both reduce and increase the energy transfer efficiency from primary producers to upper trophic levels in the pelagic and benthic food webs, respectively.

Les toxines de l’anthrax font partie de la famille des toxines A-B dans laquelle la moitié B se fixe à la membrane de la cellule permettant par la suite la translocation de la moitié A. Dans le cas de l’anthrax, la moitié B est représentée par le Protective Antigen (PA) et la moitié A par les deux protéines Edema Factor (EF) et Lethal Factor (LF). Après le recrutement par les récepteurs cellulaires (CMG2 et TEM8), PA s’organise en heptamère. Il peut fixer jusqu'à 3 ligands (EF et LF) avant d'être endocyté. Les modèles actuels de PA suggèrent que la baisse de pH à l’intérieur des endosomes permet un changement de conformation de la forme pré-pore vers la forme pore et que les ligands EF et LF passeraient au travers le pore pour entrer dans le cytoplasme. Cependant, le diamètre du pore est environ dix fois inférieur à celui des ligands (10 Å contre 100 Å). Un processus de folding/unfolding a été proposé mais demeure controversé. Afin d'identifier le processus de passage des facteurs EF et LF dans le cytoplasme, nous avons déterminé par cryo-microscopie électronique combinée avec l’analyse d’image les structures tridimensionnelles des complexes formés par PA et LF aux étapes prépore et pore. Par la suite, une étude complémentaire par dynamique moléculaire nous a permis de modéliser à haute résolution les différentes interactions qui ont lieu au sein du complexe. La structure 3D du complexe prépore combiné à 3 LF a été déterminée à une résolution de 14 Å. Nous avons aussi calculé une structure préliminaire du complexe pore également combiné à 3 LF Celles-ci n’ont jamais été résolues auparavant et leur connaissance permet d’envisager l’étude en profondeur du mécanisme infectieux de l’Anthrax in vivo. / The anthrax toxins are part of the A-B toxin family in which the B moiety binds to the cell membrane allowing subsequent translocation of the A moiety. In the case of anthrax, the B moiety consists of the Protective Antigen (PA), and the A moiety is composed of the two proteins Edema Factor (EF) and the Lethal Factor (LF). After being recruited by the cell receptors (CGM2 or TEM8), PA organizes itself into a heptamer. It can bind up to three ligands (either EF or LF) before being endocytosed. Current models suggest that the decrease of pH inside the endosomes allows a conformational change of PA from a prepore form to a pore form that allows the EF and LF ligands to pass through the pore and enter the cytoplasm. However, the pore diameter is about ten times smaller than the diameter of the ligands (10Å versus 100Å). A process of ligand folding / unfolding has been proposed, but remains controversial. To identify the mechanism by which EF and LF enter the cytoplasm, we have used cryo-electron microscopy and three-dimensional image analysis to determine the 3D structure of the PA-LF complexes in the pre-pore and pore conformations. Then, we used molecular dynamics to modelise at high resolution the different interactions that occur within the complex. The 3D structure of the pre-pore complex bound with three LF ligands has been determined at 14Å resolution. We also calculated a preliminary structure of the LF-bound pore complex. These structures have never been reported before. They provide the necessary information to study in depth the mechanism of anthrax infection in vivo.

This thesis describes the life of a family with a dying child. The objective of the thesis is to describe the experience of its members after the diagnosis has been decided, during treatment and after the child's decease. It discusses the phases of going through the disease and death of one's own child for the parents and other close persons and how such a critical event in a family's life changes its values and attitudes. The theoretical part of this thesis deals with experiencing of all stages of the child's disease by their closest persons and with the psychology of the ill child. In this context, it briefly describes the history and idea of care of the incurably ill and the possibility of family support provided by non- governmental organizations. The practical part of the thesis contains the findings of the qualitative research conducted using the phenomenology approach on how the parents supported the child in the terminal stage of their disease, what they went through during this difficult time of life and how they remember that time after certain time has elapsed. Respondents include the parents or closest persons of children aged over one year that deceased as a result of a malignant disease.

A perda de polinizadores no mundo todo, especialmente abelhas, tem sido atribuída, entre outros fatores, à intensificação do uso de inseticidas em agro ecossistemas. A nova classe química de inseticidas, os neonicotinóides, tem sido o principal alvo de investigações, sobretudo em decorrência de sua ação sistêmica que transloca a substância ativa pela planta e atinge o pólen e néctar como resíduos. Dessa forma, o presente estudo teve como objetivo verificar os efeitos do neonicotinóide tiametoxam em abelhas sociais e avaliar a possibilidade da espécie Scaptotrigona aff. depilis ser utilizada como bioindicadora de contaminação ambiental por inseticidas. Para tanto, (i) operárias forrageiras de Bombus terrestris audax, Apis mellifera e Scaptotrigona bipunctata foram submetidas à exposição contínua de alimento contaminado; (ii) operárias de Scaptotrigona aff. depilis foram expostas ao inseticida, durante o estágio larval, através do alimento e; (iii) operárias forrageiras de Scaptotrigona aff. depilis foram coletadas no meliponário da Universidade de São Paulo e arredores, e submetidas a análises químicas, para a checagem de contaminação pelos neonicotinóides tiametoxam e/ ou imidacloprido. (i) Dentre as três espécies de abelhas sociais adultas, B. terrestris audax mostrou ser a mais sensível à ação de tiametoxam, seguida de S. bipunctata e A. mellifera, verificados através do decréscimo no consumo de alimento e da longevidade. Nesse sentido, os efeitos subletais não foram influenciados pelo tamanho do corpo dos indivíduos. (ii) As operárias de Scaptotrigona aff. depilis, quando expostas a doses do inseticida em fase larval, apresentaram desenvolvimento tardio e originaram indivíduos menores e assimétricos. Tanto em abelhas adultas como em imaturas, os efeitos subletais foram evidenciados nos indivíduos expostos às maiores doses de tiametoxam nos experimentos (39.37 e 98.43µg de substância ativa/kg de xarope em adultos, ou 0.044 e 4.375ng de substância ativa/larva). (iii) A detecção de tiametoxam e imidacloprido em operárias forrageiras de Scaptotrigona aff. depilis permitiu considerar essa espécie como bioindicadora de contaminação. Nesse estudo, a mortalidade não foi parâmetro conclusivo quanto aos potenciais efeitos adversos de tiametoxam para as abelhas. O potencial de Scaptotrigona aff. depilis como espécie bioindicadora é uma importante etapa para avaliar a contaminação ambiental por neonicotinóides em abelhas sem ferrão, podendo ser utilizada em políticas públicas. / Pollinator losses all over the world, especially bees disappearing, have been attributed, among others, to the intensification of insecticide use on crops. The new chemical class of insecticides, the neonicotinoids, has been the main target of investigation, mainly due to its systemic action, which translocates the active substance for the plant and to reach the pollen and nectar as residues. Thus, this study evaluated the effects of thiamethoxam neonicotinoid on bees and the possibility of the use of Scaptotrigona aff. depilis species as bioindicator of environmental contamination by insecticides. For this, (i) Bombus terrestris audax, Apis mellifera and Scaptotrigona bipunctata forager workers were induced to continue exposure of contaminated food; (ii) Scaptotrigona aff. depilis workers were exposed to the insecticide, during its larval phase, through the larval food and; (iii) Scaptotrigona aff. depilis forager workers were collected from University of São Paulo meliponary and surroundings and analyzed, in order to check for contamination by thiamethoxam and/ or imidacloprid neonicotinoids. (i) Among the three social bee species, B. terrestris audax showed to be more sensible to the thiamethoxam action, followed by S. bipunctata and A. mellifera, verified through decreasing food consumption and longevity. Thus, the sub lethal effects were not influenced by individual body size. (ii) Scaptotrigona aff. depilis workers, when exposed to insecticide doses on larval food, caused individuals with developmental delay and were smaller and asymmetric. Both adult bees and in immature, the sub lethal effects of thiamethoxam were evidenced on individuals exposed to the highest doses in the experiments. (iii) The detection of thiamethoxam and imidacloprid in Scaptotrigona aff. depilis forager workers allowed to consider this species as bioindicator of environmental contamination. In this study, the mortality was not a conclusive parameter as to the potential adverse effects of thiamethoxam for the bees. The potential of Scaptotrigona aff. depilis species as bioindicator is an important step to assess environmental contamination by neonicotinoids on stingless bees, may be used for public policy.

Orientador: Sergio Antonio de Bortoli / Resumo: O cultivo intensivo de Brassicaceae favorece o aparecimento de algumas pragas como Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), a traça-das-crucíferas, cujos danos podem comprometer seriamente a produção. Esse inseto-praga pode ser controlado tanto com inseticidas sintéticos, como com biológicos, sendo, no entanto, usualmente utilizados os sintéticos em seu combate. A traça-das-crucíferas foi a primeira espécie de inseto a ser constatada resistência a inseticidas biológicos, com o uso indiscriminado de inseticidas sintéticos para o seu controle contribuindo também para a seleção de indivíduos tolerantes ou resistentes, além de causar a mortalidade de organismos não alvos. Sendo assim, este trabalho teve por objetivo avaliar a atividade inseticida e os efeitos subletais de duas toxinas lepidóptero-ativas de Bacillus thuringiensis, Cry1Ca e Cry2Ac, em três populações de traças-das-crucíferas, sendo uma delas suscetível (PC) e duas consideradas resistentes (Bt e NO-QA) a toxinas de B. thuringienis, em condições de laboratório. Foram realizados bioensaios de suscetibilidade com as três populações e as toxinas Cry1Ca e Cry2Ac, estimando-se a concentração letal (CL50) e os seus efeitos subletais. A toxina Cry2Ac não causou mortalidade nas lagartas das três populações, então os testes subletais foram realizados apenas com a toxina Cry1Ca que provocou mortalidade. Os parâmetros biológicos avaliados foram: período e peso pupal, sobrevivência larval e pupal, longevi... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Intensive brassics cultivation favors appearing of some pests as Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), diamondback moth (DBM), whose damage can seriously compromise production. This insect-pest can be controlled either synthetic insecticides as biological insecticides, but synthetics are usually used to combat. Diamondback moth was the first insect species to be verified resistance to biological insecticides, with indiscriminate use of synthetic insecticides for its control, also contributing to selection of tolerant or resistant individuals, as well as causing mortality on non-target organisms. Therefore, the objective of this work was to evaluate insecticide activity and sublethal effects of two lepidopteran-active toxins of Bacillus thuringiensis, Cry1Ca and Cry2Ac, on three DBM populations, one of them susceptible (PC) and two considered as resistant (Bt and NO-QA) to B. thuringiens toxins under laboratory conditions. Susceptibility bioassays were performed on the three populations and toxins Cry1Ca and Cry2Ac, estimating lethal concentration (LC50) and its sublethal effects. Cry2Ac toxin did not cause mortality on the caterpillars from the three populations, so the sublethal tests were performed only with Cry1Ca toxin. The biological parameters evaluated were: pupal period and weight, caterpillar and pupal survival, male and female longevity and fecundity. The populations showed susceptibilities to Cry1Ca toxin, with statistically equal behavio... (Complete abstract click electronic access below) / Mestre

A perda de polinizadores no mundo todo, especialmente abelhas, tem sido atribuída, entre outros fatores, à intensificação do uso de inseticidas em agro ecossistemas. A nova classe química de inseticidas, os neonicotinóides, tem sido o principal alvo de investigações, sobretudo em decorrência de sua ação sistêmica que transloca a substância ativa pela planta e atinge o pólen e néctar como resíduos. Dessa forma, o presente estudo teve como objetivo verificar os efeitos do neonicotinóide tiametoxam em abelhas sociais e avaliar a possibilidade da espécie Scaptotrigona aff. depilis ser utilizada como bioindicadora de contaminação ambiental por inseticidas. Para tanto, (i) operárias forrageiras de Bombus terrestris audax, Apis mellifera e Scaptotrigona bipunctata foram submetidas à exposição contínua de alimento contaminado; (ii) operárias de Scaptotrigona aff. depilis foram expostas ao inseticida, durante o estágio larval, através do alimento e; (iii) operárias forrageiras de Scaptotrigona aff. depilis foram coletadas no meliponário da Universidade de São Paulo e arredores, e submetidas a análises químicas, para a checagem de contaminação pelos neonicotinóides tiametoxam e/ ou imidacloprido. (i) Dentre as três espécies de abelhas sociais adultas, B. terrestris audax mostrou ser a mais sensível à ação de tiametoxam, seguida de S. bipunctata e A. mellifera, verificados através do decréscimo no consumo de alimento e da longevidade. Nesse sentido, os efeitos subletais não foram influenciados pelo tamanho do corpo dos indivíduos. (ii) As operárias de Scaptotrigona aff. depilis, quando expostas a doses do inseticida em fase larval, apresentaram desenvolvimento tardio e originaram indivíduos menores e assimétricos. Tanto em abelhas adultas como em imaturas, os efeitos subletais foram evidenciados nos indivíduos expostos às maiores doses de tiametoxam nos experimentos (39.37 e 98.43µg de substância ativa/kg de xarope em adultos, ou 0.044 e 4.375ng de substância ativa/larva). (iii) A detecção de tiametoxam e imidacloprido em operárias forrageiras de Scaptotrigona aff. depilis permitiu considerar essa espécie como bioindicadora de contaminação. Nesse estudo, a mortalidade não foi parâmetro conclusivo quanto aos potenciais efeitos adversos de tiametoxam para as abelhas. O potencial de Scaptotrigona aff. depilis como espécie bioindicadora é uma importante etapa para avaliar a contaminação ambiental por neonicotinóides em abelhas sem ferrão, podendo ser utilizada em políticas públicas. / Pollinator losses all over the world, especially bees disappearing, have been attributed, among others, to the intensification of insecticide use on crops. The new chemical class of insecticides, the neonicotinoids, has been the main target of investigation, mainly due to its systemic action, which translocates the active substance for the plant and to reach the pollen and nectar as residues. Thus, this study evaluated the effects of thiamethoxam neonicotinoid on bees and the possibility of the use of Scaptotrigona aff. depilis species as bioindicator of environmental contamination by insecticides. For this, (i) Bombus terrestris audax, Apis mellifera and Scaptotrigona bipunctata forager workers were induced to continue exposure of contaminated food; (ii) Scaptotrigona aff. depilis workers were exposed to the insecticide, during its larval phase, through the larval food and; (iii) Scaptotrigona aff. depilis forager workers were collected from University of São Paulo meliponary and surroundings and analyzed, in order to check for contamination by thiamethoxam and/ or imidacloprid neonicotinoids. (i) Among the three social bee species, B. terrestris audax showed to be more sensible to the thiamethoxam action, followed by S. bipunctata and A. mellifera, verified through decreasing food consumption and longevity. Thus, the sub lethal effects were not influenced by individual body size. (ii) Scaptotrigona aff. depilis workers, when exposed to insecticide doses on larval food, caused individuals with developmental delay and were smaller and asymmetric. Both adult bees and in immature, the sub lethal effects of thiamethoxam were evidenced on individuals exposed to the highest doses in the experiments. (iii) The detection of thiamethoxam and imidacloprid in Scaptotrigona aff. depilis forager workers allowed to consider this species as bioindicator of environmental contamination. In this study, the mortality was not a conclusive parameter as to the potential adverse effects of thiamethoxam for the bees. The potential of Scaptotrigona aff. depilis species as bioindicator is an important step to assess environmental contamination by neonicotinoids on stingless bees, may be used for public policy.

Orientador: Domingos Garrone-Neto / Resumo: Neste trabalho estudamos a composição, distribuição e história natural da comunidade de peixes em um riacho litorâneo da Mata Atlântica. Além disso, relatamos um estudo de caso envolvendo a utilização desta ictiofauna como ferramenta de divulgação e conscientização ambiental, no âmbito do projeto “Peixes do Lagamar”. Conduzimos os estudos ictiofaunísticos em três trechos do rio das Minas, no município de Cananeia, litoral sul do estado de São Paulo. Apesar de estar localizado, em sua maior parte, dentro do Parque Estadual do Lagamar de Cananeia, o rio das Minas não possuía registros a respeito de sua ictiofauna. Realizamos observações diretas (mergulho livre) e indiretas (BRUVS – Baited Remotely Underwater Video Station) durante dois anos (2017 e 2018) e coletas tradicionais (covo, picaré, puçá etc.) somente em uma campanha (set./2017). Ao todo, registramos 31 espécies, pertencentes a 14 famílias e cinco ordens, com 28 espécies no trecho a jusante, 17 no trecho intermediário e seis a montante, fato que esteve relacionado ao gradiente altitudinal existente entre os pontos de coleta. Descrevemos dois comportamentos para Geophagus brasiliensis: i) uma nova tática de forrageamento e ii) uma associação alimentar do tipo “nuclear-seguidor” com o lambari Deuterodon iguape. De forma complementar, realizamos estudos de capacidade de suporte no rio das Minas e em um outro riacho da região, o rio Mandira, identificando áreas com potencial de receber visitantes para a prática de atividad... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work, we study the composition, distribution and natural history of the fish community in a coastal stream of the Atlantic Forest. In addition, we report a case study involving the use of this ichthyofauna as a tool for dissemination and environmental awareness, within the scope of the "Peixes do Lagamar" project. We conducted the ichthyofaunistic studies in three stretches of the Rio das Minas, in the municipality of Cananeia, south coast of the state of São Paulo. Despite being located, for the most part, within the Lagamar de Cananeia State Park, the Rio das Minas had no records regarding its ichthyofauna. We conducted direct observations (snorkelling) and indirect observations (BRUVS - Baited Remotely Underwater Video Station) for two years (2017 and 2018) and traditional captures (fish trap, seine net, dip net and hook) in only one campaign (sep/2017). In total, we recorded 31 species, belonging to 14 families and five orders, with 28 species in the downstream section, 17 in the intermediate section and six upstream, a fact that was related to the altitudinal gradient existing between the collection points. We describe two behaviours for Geophagus brasiliensis: i) a new foraging tactic and ii) a "nuclear-follower" food association with tetra Deuterodon iguape. In addition, we carried out studies of carrying capacity in the Rio das Minas and another stream in the region, the Rio Mandira, identifying areas with potential to receive visitors for the practice of flot... (Complete abstract click electronic access below) / Mestre

<p>Biological invasion has become a major threat to economy, ecology, global biodiversity and ecosystem function of aquatic ecosystems. The main aim of the thesis was to study the effects of the zebra mussel <i>(Dreissena polymorpha)</i>, a versatile invasive species, on phytoplankton dynamics and ecosystem function of lakes. </p><p>In a first attempt, I compared the density of <i>Dreissena</i> and the physicochemical data of ecosystems that it invaded among North American and European lakes to identify important factors in its invasion success. Secondly, I investigated the impact of zebra mussels on phytoplankton community composition in a natural lake. Thirdly, I evaluated whether zebra mussel feeding behavior were affected by the presence of predatory waterborne cues. Finally, I examined the effect of <i>Dreissena</i> on seston stoichiometry.</p><p>A Generalized Additive Model revealed that a joint effect of surface area, mean depth, total phosphorus and calcium concentrations can explain the variability in <i>Dreissena</i> density. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics. Risk cues released by predators affected both feeding rate and prey selection of the mussels and had cascading indirect effects on phytoplankton biomass and community structure. I found that the flux in nutrients caused by differences in zebra mussel consumption lead to a variation in phytoplankton nutrient limitation.</p><p>The flexibility of zebra mussel feeding behavior and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences. The results of this thesis contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. The results suggested that zebra mussel can indirectly both reduce and increase the energy transfer efficiency from primary producers to upper trophic levels in the pelagic and benthic food webs, respectively. </p>