Many studies have reported individual differences in resting metabolic rate (RMR), the energetic cost of self-maintenance. Differences among individuals in the energetic cost of self-maintenance may influence life-history decisions and hence, fitness. In this study, we examined potential causes of intra-specific variation in RMR in zebrafish, Danio rerio. First, the repeatability of RMR was determined to check whether a single measure was reflective of future physiological performance. As predicted, RMR was repeatable over a period of three weeks. However, none of stress-coping style, baseline cortisol levels, metabolically-active organ (gill, heart, intestine and liver) mass, aggression or activity levels were correlated with RMR, i.e. none of these factors were significant contributors to individual variation in RMR. These results imply that other factors must be sought to explain the inter-individual variation in RMR observed in zebrafish.

Many studies have reported individual differences in resting metabolic rate (RMR), the energetic cost of self-maintenance. Differences among individuals in the energetic cost of self-maintenance may influence life-history decisions and hence, fitness. In this study, we examined potential causes of intra-specific variation in RMR in zebrafish, Danio rerio. First, the repeatability of RMR was determined to check whether a single measure was reflective of future physiological performance. As predicted, RMR was repeatable over a period of three weeks. However, none of stress-coping style, baseline cortisol levels, metabolically-active organ (gill, heart, intestine and liver) mass, aggression or activity levels were correlated with RMR, i.e. none of these factors were significant contributors to individual variation in RMR. These results imply that other factors must be sought to explain the inter-individual variation in RMR observed in zebrafish.

L’étude des conséquences du réchauffement climatique sur les écosystèmes aquatiques est devenue un enjeu majeur pour la recherche. Nous avons mesuré l’impact de la température des eaux douces et du changement de végétation riparienne associé au climat sur six populations de Gammarus pulex (Amphipode) vivant au nord ou au sud de la vallée du Rhône (France). Ce crustacé, largement répandu dans les eaux douces européennes, est considéré comme une espèce clé pour le fonctionnement des écosystèmes aquatiques, car, en dégradant la litière de feuilles provenant de la ripisylve, il favorise son utilisation par d’autres invertébrés. Nos résultats sur l’effet de la température sur les réserves énergétiques, la consommation d’oxygène et la survie, suggèrent que la fenêtre thermique optimale est décalée de 2-3°C entre les gammares du nord et ceux du sud. L’investissement reproducteur varie saisonnièrement, avec des stratégies différentes selon l’origine des femelles. La provenance des feuilles (méditerranéenne/continentale) influence moins leur conditionnement et la vitesse de décomposition que leur dureté initiale. Une hausse de température accélère le conditionnement et la digestion des feuilles mais influence peu leur dégradation. Nos résultats montrent que des adaptations en bordure d’aire de distribution peuvent modifier la réponse des organismes aquatiques face aux changements climatiques. De plus, un changement de la nature des litières lié au réchauffement pourrait modifier la disponibilitédes ressources trophiques au cours des saisons et ainsi le fonctionnement des écosystèmes. / The study of global warming consequences on aquatic ecosystems has become amajor issue in current scientific research. We measured the impact of water temperature and the climate-related change in riparian vegetation on six populations of Gammarus pulex (Amphipoda) living in the North and in the South of the Rhône River valley (France). This crustacean, widely distributed in European freshwaters, is considered as a key species for the freshwater ecosystems functioning as it degrades the leaf litter from the riparian area, thus favouring its subsequent use by other invertebrates. Our results of temperature effect onenergy stores, oxygen consumption, and survival suggest that the optimal thermal window shifts from 2-3°C between northern and southern gammarids. Females’ investment into reproduction changes through seasons, with different strategies according to their geographical origins. Concerning the functional point of view, the leaf litter origin(Mediterranean/continental) less influences the conditioning of leaves and the decomposition rate than their initial toughness. An increase in water temperature accelerates the conditioning and the enzymatic digestion of leaves (in gammarids guts) but slightly influences their degradation by this crustacean. Our results show that adaptations at the limit of the species geographical distribution area can change the response to climate change in aquatic organisms. Moreover, a change in the type of the leaf litter could modify the availability of trophic resource through seasons and hence the ecosystem functioning.

The ecology behind evolutionary diversification is a well studied area of research, whereas the effects of evolution on ecosystems get little attention. In line with ecological theory, evolutionary diversification of a species could influence different ecosystem aspects such as food web composition, energy flow, nutrient cycling etc. The main objective of this study was to investigate whether two diverging ecotypes (reed and chara) of Asellus aquaticus differ regarding their role in two aquatic ecosystem processes: decomposition of terrestrial leaves and grazing of periphyton. Their role in ecosystem process as well as treatment effects on fitness, measured as growth and survival, were investigated in a laboratory experiment with various levels of intra-specific competition and inter-specific interactions with the amphipod Gammarus pulex. The isopods were collected from two Swedish lakes: Lake Tåkern and Lake Fardume. These two lakes represent different history of ecotype divergence. The experimental design consisted of 2-L aquaria, each providing elm leaves (Ulmus glabra), oak leaves (Quercus roburleaves) and periphyton as food sources. Ten treatments with five replicates were applied for each lake and the experiment lasted for four weeks. The study showed that there was no significant difference between chara and reed ecotype in their functional role. However, the rate of ecosystem processes per individual decreased in competitive interactions. In high density, decomposition per dry weight consumer was low and total algae biomass was high at the end of four weeks due to intra-specific competition. Moreover, ecosystem processes were lowest in inter-specific competition between Gammarus pulex and each ecotype. Present study also shows that ecotypes from the different lakes, having different history, had different responses to mortality and growth.

Os Campos Sulinos são ecossistemas típicos da região sul do Brasil, ocorrendo no bioma Pampa e no bioma Mata Atlântica, e possuem alta riqueza florística e estrutura únicas. A dinâmica dos campos está associada à ocorrência de distúrbios naturais, como o pastejo e as queimadas, que possibilitam a renovação dos processos sucessionais, impedindo que poucas espécies dominem a comunidade. O pastejo atua como filtro ambiental selecionando espécies com determinados atributos, resultando na organização das comunidades. Nesse estudo, utilizamos dados de atributos da vegetação campestre nos biomas Pampa e Mata Atlântica, no Sul do Brasil para compreender os efeitos de diferentes intensidades de pastejo sobre os padrões e variações funcionais das comunidades vegetais. Avaliamos a variação intra-específica de atributos foliares das espécies dominantes de cada sítio e classificamos as espécies de acordo com a classificação C-S-R. Avaliamos também a variação na diversidade funcional de atributos da vegetação campestre. Observamos um padrão de variação ao longo do gradiente de pastejo, em que a exclusão de pastejo tende a selecionar indivíduos com menor SLA, e maior LA e FT Os resultados da classificação CSR mostraram uma predominância de espécies com estratégia de tolerância ao stress, enquanto espécies com características ruderais ou habilidades de competição não foram encontradas. Não houve diferença nas estratégias das plantas entre tratamentos ou entre os sítios do bioma Pampa e Mata Atlântica. As comunidades de plantas campestres diferiram entre os sítios dos biomas Pampa e Mata Atlântica quanto à sua composição de espécies. Também encontramos maior diversidade funcional nos sítios do bioma Pampa. Encontramos padrão de convergência de atributos em relação ao gradiente, em que as áreas de exclusão apresentam mais espécies perenes e entouceiradas, e menos espécies rizomatosas. Assim, confirmamos que diferentes intensidades de pastejo promovem uma resposta funcional que é muito variável, e dependente do atributo e da espécie em questão. Esse padrão de convergência encontrado pode ser causado por processos evolutivos, indicando que tanto filtros bióticos como abióticos estão atuando sobre a estrutura das comunidades. / Campos Sulinos are ecosystems typical of southern Brazil, occurring in Pampa and Atlantic Forest biomes, and hold high species richness and unique structure. Grassland dynamics are associated with the occurrence of natural disturbances such as grazing and burning, which allow the renewal of successional processes, preventing a few species dominate the community. Grazing acts as an environmental filter by selecting species with certain traits, resulting in the community assembly. In this study, we used functional traits of grassland vegetation of biomes Pampa and Atlantic Forest in southern Brazil to understand the effects of different grazing intensities on the patterns and functional changes in plant communities. We evaluated the intra-specific variation of leaf traits of the dominant species for each site and classified the species according to the C-S-R scheme. We also evaluated the changes in functional diversity of plant traits. We observed a pattern of variation along the grazing gradient, in which the grazing exclusion tends to select individuals with lower SLA and greater LA and FT CSR classification showed a predominance of species with stress-tolerance strategy, while species with ruderal characteristics or competition abilities were not found. There was no difference in the strategies of the plants between treatments or between sites in Pampa and Atlantic Forest biomes. The grassland communities differed in species composition between the sites of Pampa and Atlantic Forest biomes. We also found higher functional diversity in the Pampa biome sites. Found patterns of trait convergence along the gradient, where exclusion areas have more perennial and tussock species and less rhizomatous species. Thus, we confirm that different grazing intensities promote a functional response that is highly variable and dependent on the trait and the species concerned. Evolutionary processes, indicating that both biotic filters as abiotic are acting on the structure of communities, may cause the pattern of convergence found.

Os Campos Sulinos são ecossistemas típicos da região sul do Brasil, ocorrendo no bioma Pampa e no bioma Mata Atlântica, e possuem alta riqueza florística e estrutura únicas. A dinâmica dos campos está associada à ocorrência de distúrbios naturais, como o pastejo e as queimadas, que possibilitam a renovação dos processos sucessionais, impedindo que poucas espécies dominem a comunidade. O pastejo atua como filtro ambiental selecionando espécies com determinados atributos, resultando na organização das comunidades. Nesse estudo, utilizamos dados de atributos da vegetação campestre nos biomas Pampa e Mata Atlântica, no Sul do Brasil para compreender os efeitos de diferentes intensidades de pastejo sobre os padrões e variações funcionais das comunidades vegetais. Avaliamos a variação intra-específica de atributos foliares das espécies dominantes de cada sítio e classificamos as espécies de acordo com a classificação C-S-R. Avaliamos também a variação na diversidade funcional de atributos da vegetação campestre. Observamos um padrão de variação ao longo do gradiente de pastejo, em que a exclusão de pastejo tende a selecionar indivíduos com menor SLA, e maior LA e FT Os resultados da classificação CSR mostraram uma predominância de espécies com estratégia de tolerância ao stress, enquanto espécies com características ruderais ou habilidades de competição não foram encontradas. Não houve diferença nas estratégias das plantas entre tratamentos ou entre os sítios do bioma Pampa e Mata Atlântica. As comunidades de plantas campestres diferiram entre os sítios dos biomas Pampa e Mata Atlântica quanto à sua composição de espécies. Também encontramos maior diversidade funcional nos sítios do bioma Pampa. Encontramos padrão de convergência de atributos em relação ao gradiente, em que as áreas de exclusão apresentam mais espécies perenes e entouceiradas, e menos espécies rizomatosas. Assim, confirmamos que diferentes intensidades de pastejo promovem uma resposta funcional que é muito variável, e dependente do atributo e da espécie em questão. Esse padrão de convergência encontrado pode ser causado por processos evolutivos, indicando que tanto filtros bióticos como abióticos estão atuando sobre a estrutura das comunidades. / Campos Sulinos are ecosystems typical of southern Brazil, occurring in Pampa and Atlantic Forest biomes, and hold high species richness and unique structure. Grassland dynamics are associated with the occurrence of natural disturbances such as grazing and burning, which allow the renewal of successional processes, preventing a few species dominate the community. Grazing acts as an environmental filter by selecting species with certain traits, resulting in the community assembly. In this study, we used functional traits of grassland vegetation of biomes Pampa and Atlantic Forest in southern Brazil to understand the effects of different grazing intensities on the patterns and functional changes in plant communities. We evaluated the intra-specific variation of leaf traits of the dominant species for each site and classified the species according to the C-S-R scheme. We also evaluated the changes in functional diversity of plant traits. We observed a pattern of variation along the grazing gradient, in which the grazing exclusion tends to select individuals with lower SLA and greater LA and FT CSR classification showed a predominance of species with stress-tolerance strategy, while species with ruderal characteristics or competition abilities were not found. There was no difference in the strategies of the plants between treatments or between sites in Pampa and Atlantic Forest biomes. The grassland communities differed in species composition between the sites of Pampa and Atlantic Forest biomes. We also found higher functional diversity in the Pampa biome sites. Found patterns of trait convergence along the gradient, where exclusion areas have more perennial and tussock species and less rhizomatous species. Thus, we confirm that different grazing intensities promote a functional response that is highly variable and dependent on the trait and the species concerned. Evolutionary processes, indicating that both biotic filters as abiotic are acting on the structure of communities, may cause the pattern of convergence found.

Os Campos Sulinos são ecossistemas típicos da região sul do Brasil, ocorrendo no bioma Pampa e no bioma Mata Atlântica, e possuem alta riqueza florística e estrutura únicas. A dinâmica dos campos está associada à ocorrência de distúrbios naturais, como o pastejo e as queimadas, que possibilitam a renovação dos processos sucessionais, impedindo que poucas espécies dominem a comunidade. O pastejo atua como filtro ambiental selecionando espécies com determinados atributos, resultando na organização das comunidades. Nesse estudo, utilizamos dados de atributos da vegetação campestre nos biomas Pampa e Mata Atlântica, no Sul do Brasil para compreender os efeitos de diferentes intensidades de pastejo sobre os padrões e variações funcionais das comunidades vegetais. Avaliamos a variação intra-específica de atributos foliares das espécies dominantes de cada sítio e classificamos as espécies de acordo com a classificação C-S-R. Avaliamos também a variação na diversidade funcional de atributos da vegetação campestre. Observamos um padrão de variação ao longo do gradiente de pastejo, em que a exclusão de pastejo tende a selecionar indivíduos com menor SLA, e maior LA e FT Os resultados da classificação CSR mostraram uma predominância de espécies com estratégia de tolerância ao stress, enquanto espécies com características ruderais ou habilidades de competição não foram encontradas. Não houve diferença nas estratégias das plantas entre tratamentos ou entre os sítios do bioma Pampa e Mata Atlântica. As comunidades de plantas campestres diferiram entre os sítios dos biomas Pampa e Mata Atlântica quanto à sua composição de espécies. Também encontramos maior diversidade funcional nos sítios do bioma Pampa. Encontramos padrão de convergência de atributos em relação ao gradiente, em que as áreas de exclusão apresentam mais espécies perenes e entouceiradas, e menos espécies rizomatosas. Assim, confirmamos que diferentes intensidades de pastejo promovem uma resposta funcional que é muito variável, e dependente do atributo e da espécie em questão. Esse padrão de convergência encontrado pode ser causado por processos evolutivos, indicando que tanto filtros bióticos como abióticos estão atuando sobre a estrutura das comunidades. / Campos Sulinos are ecosystems typical of southern Brazil, occurring in Pampa and Atlantic Forest biomes, and hold high species richness and unique structure. Grassland dynamics are associated with the occurrence of natural disturbances such as grazing and burning, which allow the renewal of successional processes, preventing a few species dominate the community. Grazing acts as an environmental filter by selecting species with certain traits, resulting in the community assembly. In this study, we used functional traits of grassland vegetation of biomes Pampa and Atlantic Forest in southern Brazil to understand the effects of different grazing intensities on the patterns and functional changes in plant communities. We evaluated the intra-specific variation of leaf traits of the dominant species for each site and classified the species according to the C-S-R scheme. We also evaluated the changes in functional diversity of plant traits. We observed a pattern of variation along the grazing gradient, in which the grazing exclusion tends to select individuals with lower SLA and greater LA and FT CSR classification showed a predominance of species with stress-tolerance strategy, while species with ruderal characteristics or competition abilities were not found. There was no difference in the strategies of the plants between treatments or between sites in Pampa and Atlantic Forest biomes. The grassland communities differed in species composition between the sites of Pampa and Atlantic Forest biomes. We also found higher functional diversity in the Pampa biome sites. Found patterns of trait convergence along the gradient, where exclusion areas have more perennial and tussock species and less rhizomatous species. Thus, we confirm that different grazing intensities promote a functional response that is highly variable and dependent on the trait and the species concerned. Evolutionary processes, indicating that both biotic filters as abiotic are acting on the structure of communities, may cause the pattern of convergence found.

In basidiomycetous fungi, the viability of gametes is an important component of sexual fitness and can have implications for speciation events. Prior estimates of basidiospore germination are highly variable and the occurrence of reproduction between these lineages suggests that reproductive isolation is incomplete. Genetic incompatibilities during meiosis have been attributed to much of the offspring inviability. However, the influence of environmental factors on basidiospore germination in Cryptococcus are not well known. In this study, we used human opportunistic yeast pathogens, Cryptococcus neoformans and Cryptococcus deneoformans, as models to investigate the potential effects of selected genetic and environmental factors on basidiospore germination. We evaluated basidiospore germination of six genetic crosses by pairing a total of five strains, three intraspecific crosses and three interspecific crosses, between C. neoformans and C. deneoformans. The offspring of genetic crosses were incubated under multiple media and temperature treatments and scored for their germination ability. In general, spores from intraspecific crosses had greater germination potential than those from interspecific crosses. Growth under high temperatures was the most significant influence on basidiospore germination on these crosses. Furthermore, there were notable interaction effects between environmental factors and parental strains or strain pairs on basidiospore germination. The interaction between the sex-specific genes and environmental pressures impact reproductive barriers and blur species distinctions within the Cryptococcus neoformans species complex. And so, reduced viability of hybrid offspring can have implications for Cryptococcus speciation, ecology, and pathogenesis as hybridization events are an effective method of increasing pathogenicity, expanding species distributions and increasing tolerance to novel environments or hosts. / Thesis / Master of Science (MSc) / In basidiomycetous fungi, the viability of gametes is an important component of sexual fitness and can have implications for speciation events. The Cryptococcus neoformans species complex are a group of opportunistic pathogens, for which hybridization can be facilitated readily under laboratory conditions, creating offspring that are generally completely inviable or have low germination potential. Antagonistic genetic interactions are mostly responsible for offspring inviability, yet the impacts of environmental factors is not known. Multiple genetic crosses between Cryptococcus strains were used as a model to investigate species relationships by examining the impacts of genetic and environmental factors on offspring germination potential.

FundaÃÃo de Amparo à Pesquisa do Estado do Cearà / O conhecimento sobre relaÃÃes trÃficas à essencial para a compreensÃo da ecologia evolutiva de espÃcies, assim como no entendimento de como as comunidades se estruturam. O uso de um mesmo alimento por duas ou mais espÃcies pode levar ao surgimento de mecanismos capazes de amenizar a competiÃÃo inter-especÃfica, como a diversificaÃÃo dos itens consumidos. Dentro de populaÃÃes, a competiÃÃo elevada pode resultar em variaÃÃes inter-individuais quanto ao consumo dos recursos trÃficos disponÃveis. Estudos sobre a ecologia trÃfica de anuros tÃm analisado: i) Itens alimentares que constam na dieta; ii) VariaÃÃo sazonal na dieta e estratÃgia alimentares; iii) VariaÃÃes ontogenÃticas na dieta; e iv) VariaÃÃes inter-individuais na dieta. No presente estudo, indivÃduos de uma populaÃÃo de Rhinella hoogmoedi em Guaramiranga (remanescente de floresta Ãmida no nordeste brasileiro), foram coletados mensalmente de julho de 2009 atà junho de 2010 para investigar os recursos trÃficos consumidos pela espÃcie, utilizando o mÃtodo de lavagem estomacal (âstomach-flushâ). Foi caracterizada a dieta e sua variaÃÃo em funÃÃo do tamanho, da sazonalidade e entre indivÃduos. Dentre os 130 indivÃduos analisados foi encontrado um total de 2078 itens alocados em 16 categorias de presa. Tamanho (comprimento e volume) das presas estive relacionado com tamanho (comprimento) do predador. Formicidae, Acari, Coleoptera e Isoptera foram os principais itens consumidos. Houve variaÃÃo ontogenÃtica nos padrÃes de alimentaÃÃo, com indivÃduos menores que 15 mm consumindo uma maior proporÃÃo de Acari e aqueles maiores que 15 mm consumindo uma maior proporÃÃo de Formicidae. Houve uma pequena variaÃÃo na dieta de R. hoogmoedi entre as estaÃÃes seca e chuvosa. Foi observada uma baixa tendÃncia de R. hoogmoedi em apresentar especializaÃÃo intra-especÃfica. à provÃvel que a especializaÃÃo em determinados itens alimentares (Formicidae e Acari) por parte da espÃcie, limite, por meio de mecanismos de trade-off, o espectro de possÃveis presas consumÃveis, reduzindo as possibilidades de variaÃÃes inter-individuais mais representativas. SÃo necessÃrios estudos que avaliem como o grau de especializaÃÃo intra-especÃfica varia em funÃÃo dos hÃbitos alimentares das demais espÃcies de anuros presentes na comunidade, contribuindo para o entendimento de como relaÃÃes alimentares podem atuar na ecologia evolutiva deste tÃxon. AlÃm disso, à recomendÃvel que estudos futuros busquem quantificar a disponibilidade de presas no ambiente, contribuindo para um melhor entendimento do fluxo de matÃria entre nÃveis trÃficos. O intenso desmatamento observado nas florestas Ãmidas de altitude do semi-Ãrido nordestino, atrelado aos constantes relatos de declÃnio em populaÃÃes de anuros e a escassez de dados sobre o elevado nÃmero de espÃcies evidenciam a urgÃncia de pesquisas desta natureza. / The understanding of trophic relations among species is essential for the comprehension of their ecological evolutionary history, as well as in the understanding of how communities are structured. The consumption of the same food resource by two or more species may result in the evolution of mechanisms capable of reducing this inter- specific competition, with the diversification of the items consumed. In populations, high levels of competition may result in inter-individual variations related to the consumption of available resources. Studies on anuran trophic ecology have analyzed: i) food items present in the diet; ii) seasonal variation in diet and feeding strategies; iii) ontogenetic variation in diet; and iv) inter-individual variation in diet. In the present study, individuals from a population of Rhinella hoogmoedi Caramaschi e Pombal, 2006 from Guaramiranga (reminiscent of humid forest in northeastern Brazil) were collected monthly from July 2009 to June 2010 in order to investigate the trophic resources consumed by the species, using the stomach-flush method. Food items were identified and their variation according to size, season and between individuals verified. A total of 2078 items in 16 prey categories were found among the 130 analyzed individuals. Prey size (length and volume) were related to predator size (snout-vent lenght). Formicidae, Acari, Coleoptera and Isoptera were the most consumed items. Ontogenetic variation in diet was observed, with individuals smaller than 15 mm consuming mainly Acari and those above 15 mm consuming mainly Formicidae. Diet varied slightly seasonally, and a low tendency in individual specialization was observed. It is possible that the specialization in certain food items (Formicidae and Acari) might limit, through mechanisms of trade-off, the amount of available prey, reducing the occurrence of individual specialization. Studies that evaluate how the degree of intra-specific variation changes according to feeding habits among other anurans in the community may contribute to the understanding of how trophic relations might act in the evolution of these taxa. Besides this, it is recommended that future studies try to quantify the amount of prey available in the environment, contributing to the understanding of energy flux between trophic levels. Intense forest removal observed in the humid forests of Brazilianâs northern semi-arid, associated with the constant reports on anuran declining and the lack of data on many species, points to the urgency for this type of study.

Le cannibalisme intra-cohorte est l’acte de tuer et consommer tout ou partie d’un individu conspécifique du même âge. Longtemps considéré comme un artefact d’élevage, le cannibalisme est maintenant admis comme un phénomène naturel pouvant être soumis à des mécanismes de sélection. Chez les Téléostéens, il est majoritairement référencé au niveau des premiers stades de vie. En condition d’élevage, plusieurs facteurs biotiques et abiotiques ont été testés sans réussir à totalement l’éliminer chez de nombreuses espèces. Dans ce contexte, cette thèse a pour objectifs de mieux comprendre la mise en place et le maintien du cannibalisme, chez le sandre, en se focalisant sur le lien entre cannibalisme, personnalité et mise en place de l’ichtyophagie. Cette thèse a été divisée en trois parties : (i) description du cannibalisme chez les premiers stades de vie du sandre et étude de l’influence de certains facteurs d’élevage, (ii) détermination des traits de personnalité chez les juvéniles, et mise en évidence de l’apparition du comportement piscivore chez les larves, (iii) recherche des liens entre cannibalisme, personnalité et mise en place de l’ichtyophagie. Cette thèse a montré que les facteurs d’élevage testés n’ont pas d’influence sur le cannibalisme. Elle a permis de démontrer l’existence de syndromes comportementaux dès les premiers stades de vie, que l’ichtyophagie ne se mettait pas en place au même âge chez tous les individus et que celle-ci était liée à la personnalité. Nos résultats montrent, également, que le cannibalisme chez les premiers stades de vie du sandre serait lié à la mise en place d’une ichtyophagie précoce et non à une personnalité particulière. On peut en déduire que le cannibalisme ne repose pas, au cours du développement, sur les mêmes caractéristiques individuelles que l’ichtyophagie / Intra-cohort cannibalism is the act of killing and consuming the whole, or major part, of a conspecific individual of the same age. Most often considered as an artefact of captive conditions, it is now assumed that cannibalism is a natural phenomenon, which could be submitted to selection. In Teleosts, it is mostly found in early life stages. In rearing conditions, several biotic and abiotic factors have been already tested, yet without successfully stop it in several species. In this context, the aim of this thesis is to better understand the onset and the stability of cannibalism, in pikeperch, by focusing on the link between cannibalism, personality and the onset of ichtyophagy. This study comprised three main parts aiming at: (i) describing the cannibalism in early life stages and studying the impact of rearing factors, (ii) determining personality traits in juveniles and describing the onset of ichtyophagy in larvae, (iii) searching the link between cannibalism, personality and onset of ichtyophagy. This thesis showed that rearing factors have no impact on cannibalism. Furthermore, we found behavioural syndromes in early life stages and that the onset of ichtyophagy did not occur at the same time for all individuals. Our results highlight that cannibalism seems to be linked to the onset of ichtyophagy rather than individual personality. In conclusion, cannibalism is not due, throughout the development, to the same individual characteristics than ichtyophagy