Neste trabalho foram caracterizados cinco fotopolimerizadores, Visilux 2, Resilux, Fibralux, Translux III e Primelite. Inicialmente foram obtidos os espectros de emissão das cinco fontes de luz com um monocromador, e a estes espectros foram ajustadas funções gaussianas. Os melhores ajustes foram obtidos com um somatório de funções gaussianas, que originaram uma função matemática característica para cada uma das fontes de luz. Foi obtido também o espectro de absorção ótica da resina composta utilizada, no intervalo de 350-600 nm do espectro eletromagnético, e observou-se que havia uma absorção maior para comprimentos de onda menores. Foram calculados os valores dos coeficientes de atenuação linear para as lamínulas e para as amostras de resina, e observou-se que para uma mesma fonte de luz, haviam variações dos valores do coeficiente de atenuação linear para as diferentes espessuras, tanto das lamínulas como das amostras, concluindo-se que o sistema não estava em equilíbrio. As fontes de luz utilizadas foram ordenadas de acordo com a sua eficiência na polimerização da resina, através dos valores de dureza durante a polimerização da amostra, na seguinte ordem: Visilux 2, Translux III, Resilux, Fibralux, Primelite. / In this work, five photopolymerizators was characterized, Visilux 2, Resilux, Fibralux, Translux III and Primelite. Initially the emission specter from five light sources was obtained with a monochromator, and to these specters was adjusted gaussians functions. The better adjustments was obtained with a sum of gaussian functions, originating a caracteristic mathematical function to each light source. The resin's optical absortion specter was obtained in the 350-600 nm interval from eletromagnetic specter, and was observed that was greater absorption for smaller weavelength. The values of linear attenuation coefficient from slabs and samples was calculated, and was observed that for one light source, there was variations in the values of linear attenuation coefficient to differents thicknesses, both to the slabs and the samples, concluding that the sistem was not in equilibrium. The light sources used was disposed in agreement to their efficience in the resin's polymerization, through the values of the hardness during the photopolymerization, in the order: Visilux 2, Translux III, Resilux, Fibralux and Primelite.

Ettlia oleoabundans, a freshwater green microalga, was grown under different environmental conditions to study its growth, lipid yield and quality for a better understanding of the fundamental physiology of this oleaginous species. E. oleoabundans showed steady increase in biomass under low temperature and low light intensity, and at high temperature lipid cell content significantly increased independent of nitrate depletion. Studies on light quality showed that red light treatment did not change the biomass concentration, but stimulated lipid yield especially oleic acid, the most desirable biodiesel precursor. Moreover, no photoreversibility in lipid production was observed when applying alternating short-term red and far-red lights, which left the phytochrome effect still an open question. In addition, carbon dioxide enrichment via an air sparging system significantly boosted exponential growth and increased carbon conversion efficiency. Finally, a practical study demonstrated the feasibility of growing E. oleoabundans for high lipid production using a diluted agricultural anaerobic waste effluent as the medium. Together, these studies showed the potential of E. oleoabundans as a promising high yield feedstock for the production of high quality biodiesel.

Orientador: Ciro Cesar Zanini Branco / Banca: Orlando Necchi Junior / Banca: Carla Ferragut / Resumo: Os efeitos provocados pela variação quantitativa e qualitativa da luz incidente sobre a estrutura das comunidades de macroalgas lóticas em riachos da região Centro-Sul do estado do Paraná foram investigados a partir de experimentos utilizando-se amostradores com substratos artificiais que modulam a quantidade e qualidade da luz incidente. Os resultados reveleram que as respostas das divisões algais isoladamente foram mais claras do que àquelas observadas para as comunidades de macroalgas como um todo. As algas verdes mostraram-se melhores adaptadas as condições com maiores energias luminosas. A espécie de cianobactéria registrou clara preferência por comprimentos de onda mais longos (faixa do vermelho). As algas vermelhas apesar de apresentarem baixos valores de abundância, aparentemente, preferiram condições levemente sombreadas e, como as cianobactérias, apresentaram maiores valores de abundância quando submetidas a luz vermelha. Neste contexto, o aparato fotossintético característico de cada divisão algal parece ser determinante para os seus comportamentos ecológicos, uma vez que desempenham funções adaptativas diante das diferentes condições de luminosidade / Abstract: The effects of light intensity and quality on the structure of lotic macroalgal communities in streams from the mid-southern region of Paraná State were investigated using artificial substrata that simulate different levels of light and specific wavelengths. The results showed that the abundance values of each algal divisions were clearer to that observed to global macroalgae communities. The green algae were better adaptated on higher light energies conditions. The cianobacteria species reported a clear preference to longer wavelengths (red light). Red algae, on the other hand, despite of the low abundance values, apparently prefer lightly shaded conditions and like blue-green algae, they showed better colonization on the red light. In this context, the characteristic photosynthetic apparatus of each division seems to be determinant to the ecological behavior of these communities once they play an important adaptative role face to the different light conditions / Mestre

In order to understand the migration patterns of migrating birds, it is necessary to understand whenand where to they migrate. Many of these birds are very small and thus cannot carry heavy sensors;hence it is necessary to be able to perform positioning using a very small sensor. One way to do this isto use a light-intensity sensor. Since the sunrise and sunset times are known given time and position onthe earth, it is possible to determine the global position using light intensity. Light intensity increasesas the sun rises. Data sets from several calibration sensors, mainly from different locations in Sweden, have been examinedin different ways in order to get an understanding of the measurements and what affects them. Inorder to perform positioning, it is necessary to know the solar elevation angle, which can be computedif the time and position are known, as is the case for the calibration sensors. This has been utilized toidentify a mapping from measured light intensity to solar elevation angle, which is used to computepseudo-measurements for target tracking, described below. In this thesis, positioning is performed using methods from the field of target tracking. This is doneboth causally (filtering) and non-causally (smoothing). There are certain problems that arise; firstly,the measured light intensity can be attenuated due to weather conditions such as cloudiness, which ismodelled as a time-varying offset. Secondly, the sensor can be shadowed causing outliers in the data.Furthermore, birds are not always in a migratory state, they oftentimes stay in one place. The lattertwo phenomena are modelled using an Interacting Multiple Model (IMM) where they are representedas discrete states, corresponding to different models.

Nannochloropsis oculata is one of promising oleaginous microalga, containing a plenty of fat which can be extracted and transformed into biodiesel. The purpose of this study is to develop a closed system, Outdoor Temperature Controllable Photobioreactor System (OTCPS), to cultivate the algae in pure and massive quantity. In this research, the seawater from Sizihwan is used as the cultivation liquid. Lambert-Beer¡¦s Law is adopted to calculate the attenuation coefficient of light intensity in a water column. By adjusting the water depth, not only the light intensity but also the water temperature could be controlled at the optimal situation and thus avoids unfavorable temperature changing in harsh weather. Therefore to establish the relationship of light intensity and water temperature is critical for the success of growing microalgae in outdoor conditions. The temperature variation of culture medium can be explained by the heat transfer theorem. In this study, the heat radiation mechanism and the first order of Fourier heat conductivity were adopted to simulate the liquid temperature change. The simulation results have shown good agreement with the filed data especially during daytime. The experimental results reveal that the winter grow rate of Nannochloroposis oculata is 0.33 d-1 , while the summer growth rate is only 0.20 d-1 . This may imply that the high temperature is an inhibition to the growth of Nannochloroposis oculata. Besides when the cell density of microalgae is getting higher, each individual alga may create mutual shading effect and thus reduce the photosynthetic efficiency. In conclusion, the proposed photobioreactor has been successfully tested in summer, autumn, and winter at Kaohsiung, in the south of Taiwan. This indicates that this device can be broadly used in the subtropic zone

While understanding the kinetics of algae growth plays an important role in improving algae cultivation technology, none of the existing kinetic models are able to describe algae growth when more than three growth limiting factors are involved. A model was developed in this study to describe algae growth in a photobioreactor. Two expressions were proposed based on the Monod model to relate the specific growth rate of algae to the concentration of nitrogen, phosphorus, inorganic carbon and light intensity in the culture media. Algal biomass concentration as a function of time was calculated by solving mass and energy balances around the photobioreactor. Model simulations were compared with the experimental data from the cultivation of wild type algae in a semi-continuous culture of a completely mixed photobioreactor. There were minor differences between the model results from using the two proposed expressions of the specific growth rate of algae. Biomass concentration simulated by the model followed the same pattern as the measured concentration. However, there was discrepancy between the model output and the experimental results, because of variability from environmental conditions during the experiment and some environmental factors such as temperature were not considered in the model. Also, most of the model's parameters were either derived theoretically or obtained from literature instead of being measured directly. It was found through sensitivity analysis that the maximum biomass density predicted by the model is very sensitive to the maximum specific growth rate for carbon, maximum growth yield and higher heating value of algae. Results from running the model for a continuous culture of the same photobioreactor, showed that the minimum hydraulic retention time for the growth of algae will be 30 days. Further investigations are needed to get more accurate data for sensitive parameters so algae growth can be predicted more accurately. Future work towards integrating other factors including temperature, pH, inhibition factors and decay rate in the kinetic expression, will lead to a better prediction of algae growth

Effects of temperature and light intensity on photofermentative hydrogen production by Rhodobacter capsulatus DSM1710 by use of acetic and lactic acids as substrates were studied. Experiments were conducted at 20, 30 and 38oC incubator temperatures under light intensities in the 1500 &ndash / 7000 lux range. pH of the medium and quantity of hydrogen forming together with quantity of biomass, and concentrations of acetic, lactic, formic, butyric and propionic acids in the medium were determined periodically. Growth took place and hydrogen was produced under all experimental conditions. Growth was found to increase with increase in temperature but to decrease with increase in light intensity. Total hydrogen produced increased with light intensity up to 6000 lux at 20oC, 5000 lux at 30oC and 3000 lux at 38oC and decreased beyond these values. Medium temperature of about 30oC was found to be optimum for cumulative hydrogen. pH was found to increase slightly and almost all of lactic acid and most of acetic acid was consumed while formic, butyric and propionic acids were first formed and then consumed in the experiments. Growth data fitted well to the logistic model and hydrogen production data fitted well to the Modified Gompertz Model. Lactic acid was found to be almost completely consumed by first order kinetics in early times. Consumption of acetic acid was found to follow zero order kinetics in the early times when lactic acid existed in the system but the order shifted to one later when most of lactic acid was consumed.

PhD / The waratah, Telopea speciosissma and its hybrids with other Telopea species, is an Australian native species grown for domestic and export cut flower markets. The showy floral bracts surrounding the inflorescence often suffer from bract browning, reducing the market value and export potential of the blooms. Prior to this project, the physiological cause of the disorder was not known, although bract browning had been attributed to water stress, heat stress, high light (particularly after frost), wind and mechanical damage. Bract browning was reportedly minimised when waratahs were grown in shaded conditions, although the reduction in browning by shade had not been quantified. The aim of this project was to examine the physiological cause of the bract browning disorder and investigate methods for control. The appearance, timing, and severity of the bract browning disorder was initially characterised by dissecting waratah buds from commercial growers throughout NSW. Bract browning became evident in the six to eight weeks prior to harvest, coinciding with rapid bract and flower expansion. A survey of commercial waratah growers, initiated by NSW Agriculture and the Waratah Industry Network and analysed by the author, corroborated these results. The survey showed that bract browning was observed in all years between 1999 and 2003, with relatively high severity (scores from three to five out of a possible five) in three of those years. Scores or counts of brown bracts were used to assess the severity of the disorder, the latter including the number of senesced floral bracts following browning as a measure of browning severity. The position and timing of browning suggest light damage or localised calcium deficiency could play a role in the development of browning. The bract browning disorder was studied in further experiments on potted red waratahs of cultivars ‘Fire and Brimstone’, ‘Olympic Flame’ and ‘Sunflare’ at the Mount Annan Botanic Garden; on commercially grown ‘Wirrimbirra White’ waratahs at Jervis Bay; and on natural populations in the Royal National Park. The effect of calcium nutrition on bract browning was studied at Mount Annan in 2001 and 2002, testing the hypothesis that browning may be caused by a localised calcium deficiency similar to lettuce tipburn or poinsettia bract necrosis. Waratah bracts had significantly less calcium in all fractions than leaves, with the procedure of Ferguson et al. (1980) used to separate physiologically active, oxalate associated and residual calcium. Calcium chloride sprays applied to developing bracts increased total bract calcium by about 25% in ‘Sunflare’ and ‘Olympic Flame’ cultivars, but not in ‘Fire and Brimstone’. However, application of calcium as a spray to the developing bracts, or as gypsum to the potting medium did not significantly reduce bract browning scores. These results and the development of bract browning in exposed, rather than enclosed tissue, suggest that factors other than calcium are involved in the development of bract browning. The light environment (full sun or 50% shade cloth) had a greater effect than irrigation frequency on bract browning of ‘Sunflare’ and ‘Olympic Flame’ waratahs in 2001. Waratahs grown under 50% shade cloth showed less bract browning at flower maturity than waratahs grown in full sun. This result was corroborated by subsequent experiments in 2002 and 2003. For example, in 2002, shade cloth reduced browning and bract loss by 30-60% at flower maturity, compared to waratahs grown in full sun. Shading waratahs from bud initiation in late summer (December-January) or bud opening in late winter (July-August) was equally effective in reducing browning. Shade cloth (50%) significantly reduced the light intensity experienced by waratah plants throughout the day, as well as reducing the daily maximum temperature and minimum relative humidity. Natural shade conditions at the Royal National Park effectively prevented browning of floral bracts, although the smaller basal bracts still turned brown and senesced. The development of bract browning as waratahs matured was linked to the development of chronic photoinhibition, measured as a decrease in predawn photosynthetic efficiency using chlorophyll fluorescence techniques. Waratah bracts were unable to maintain efficient photosynthesis in full sun conditions and reached saturation of non-photochemical quenching at lower light intensities than leaves. This suggests that bract tissue is adapted to a lower light environment than leaf tissue. Outer bracts had a significantly lower photosynthetic efficiency (Fv/Fm) than leaves early in flower development, as they were exposed to the environment for a prolonged period. Outer bracts also began to senesce towards flower maturity, particularly in full sun, increasing their susceptibility to damage. Inner waratah bracts were able to maintain a high photosynthetic efficiency prior to exposure, but photosynthetic efficiency decreased significantly at the intermediate stage of floral development, as inner bracts were no longer protected by outer bracts. Waratah leaves were more resilient than bracts, and did not suffer from chronic photoinhibition or browning during flower development. The increased susceptibility of bracts to photoinhibition and browning parallels results in other species, such as Dendrobium, where floral tissue experiences photoinhibition, bleaching and necrosis at lower light intensities than leaf tissue. Bracts on shaded waratahs maintained higher chlorophyll, carotenoid and anthocyanin concentrations than sun-exposed bracts, giving more intense flower colour and higher quality blooms. The significant decrease in bract pigmentation in the sun is likely to be a result of pigment destruction following photoinhibition, and has been noted in susceptible tissues of other species, such as Illicium (star anise) leaves. The presence of anthocyanins did not reduce bract browning in waratahs, with the concentration of UV-absorbing compounds showing a stronger positive correlation with protection from photoinhibition than the concentration of anthocyanins. However, anthocyanin concentrations were significantly lower in sun-exposed bracts, and brown compounds appeared to replace anthocyanins in the epidermal cells of brown bracts. Thus, it seems likely that browning in waratah bracts is the visible manifestation of oxidative damage to cell components, following chronic photoinhibition. Light-induced oxidative damage can lead to yellowing and pigment bleaching, lipid peroxidation, the development of necrotic lesions and senescence. However, lipid peroxidation as measured by the malionaldehyde assay gave no indication of oxidative damage to waratah bract tissue. This was probably due to the presence of anthocyanins and other flavonoids and sugars other than sucrose in bract tissue interfering with the colourimetric measurement of thiobarbituric acid reactive substances. The extensive planting of waratahs in NSW in the last five years suggests that the total value of lost production due to bract browning is likely to increase in the future. The browning disorder may also prevent the establishment of waratahs in other markets, as international cut-flower markets demand high quality blooms free from blemishes. The results of this study show that bract browning, photoinhibition and pigment loss are minimised by protecting waratahs from high light intensities from bud opening until harvest. However, the consequences of shading waratahs throughout the year require further investigation, as does the use of different percentages of shade cloth or other methods to reduce incident light.

PhD / The waratah, Telopea speciosissma and its hybrids with other Telopea species, is an Australian native species grown for domestic and export cut flower markets. The showy floral bracts surrounding the inflorescence often suffer from bract browning, reducing the market value and export potential of the blooms. Prior to this project, the physiological cause of the disorder was not known, although bract browning had been attributed to water stress, heat stress, high light (particularly after frost), wind and mechanical damage. Bract browning was reportedly minimised when waratahs were grown in shaded conditions, although the reduction in browning by shade had not been quantified. The aim of this project was to examine the physiological cause of the bract browning disorder and investigate methods for control. The appearance, timing, and severity of the bract browning disorder was initially characterised by dissecting waratah buds from commercial growers throughout NSW. Bract browning became evident in the six to eight weeks prior to harvest, coinciding with rapid bract and flower expansion. A survey of commercial waratah growers, initiated by NSW Agriculture and the Waratah Industry Network and analysed by the author, corroborated these results. The survey showed that bract browning was observed in all years between 1999 and 2003, with relatively high severity (scores from three to five out of a possible five) in three of those years. Scores or counts of brown bracts were used to assess the severity of the disorder, the latter including the number of senesced floral bracts following browning as a measure of browning severity. The position and timing of browning suggest light damage or localised calcium deficiency could play a role in the development of browning. The bract browning disorder was studied in further experiments on potted red waratahs of cultivars ‘Fire and Brimstone’, ‘Olympic Flame’ and ‘Sunflare’ at the Mount Annan Botanic Garden; on commercially grown ‘Wirrimbirra White’ waratahs at Jervis Bay; and on natural populations in the Royal National Park. The effect of calcium nutrition on bract browning was studied at Mount Annan in 2001 and 2002, testing the hypothesis that browning may be caused by a localised calcium deficiency similar to lettuce tipburn or poinsettia bract necrosis. Waratah bracts had significantly less calcium in all fractions than leaves, with the procedure of Ferguson et al. (1980) used to separate physiologically active, oxalate associated and residual calcium. Calcium chloride sprays applied to developing bracts increased total bract calcium by about 25% in ‘Sunflare’ and ‘Olympic Flame’ cultivars, but not in ‘Fire and Brimstone’. However, application of calcium as a spray to the developing bracts, or as gypsum to the potting medium did not significantly reduce bract browning scores. These results and the development of bract browning in exposed, rather than enclosed tissue, suggest that factors other than calcium are involved in the development of bract browning. The light environment (full sun or 50% shade cloth) had a greater effect than irrigation frequency on bract browning of ‘Sunflare’ and ‘Olympic Flame’ waratahs in 2001. Waratahs grown under 50% shade cloth showed less bract browning at flower maturity than waratahs grown in full sun. This result was corroborated by subsequent experiments in 2002 and 2003. For example, in 2002, shade cloth reduced browning and bract loss by 30-60% at flower maturity, compared to waratahs grown in full sun. Shading waratahs from bud initiation in late summer (December-January) or bud opening in late winter (July-August) was equally effective in reducing browning. Shade cloth (50%) significantly reduced the light intensity experienced by waratah plants throughout the day, as well as reducing the daily maximum temperature and minimum relative humidity. Natural shade conditions at the Royal National Park effectively prevented browning of floral bracts, although the smaller basal bracts still turned brown and senesced. The development of bract browning as waratahs matured was linked to the development of chronic photoinhibition, measured as a decrease in predawn photosynthetic efficiency using chlorophyll fluorescence techniques. Waratah bracts were unable to maintain efficient photosynthesis in full sun conditions and reached saturation of non-photochemical quenching at lower light intensities than leaves. This suggests that bract tissue is adapted to a lower light environment than leaf tissue. Outer bracts had a significantly lower photosynthetic efficiency (Fv/Fm) than leaves early in flower development, as they were exposed to the environment for a prolonged period. Outer bracts also began to senesce towards flower maturity, particularly in full sun, increasing their susceptibility to damage. Inner waratah bracts were able to maintain a high photosynthetic efficiency prior to exposure, but photosynthetic efficiency decreased significantly at the intermediate stage of floral development, as inner bracts were no longer protected by outer bracts. Waratah leaves were more resilient than bracts, and did not suffer from chronic photoinhibition or browning during flower development. The increased susceptibility of bracts to photoinhibition and browning parallels results in other species, such as Dendrobium, where floral tissue experiences photoinhibition, bleaching and necrosis at lower light intensities than leaf tissue. Bracts on shaded waratahs maintained higher chlorophyll, carotenoid and anthocyanin concentrations than sun-exposed bracts, giving more intense flower colour and higher quality blooms. The significant decrease in bract pigmentation in the sun is likely to be a result of pigment destruction following photoinhibition, and has been noted in susceptible tissues of other species, such as Illicium (star anise) leaves. The presence of anthocyanins did not reduce bract browning in waratahs, with the concentration of UV-absorbing compounds showing a stronger positive correlation with protection from photoinhibition than the concentration of anthocyanins. However, anthocyanin concentrations were significantly lower in sun-exposed bracts, and brown compounds appeared to replace anthocyanins in the epidermal cells of brown bracts. Thus, it seems likely that browning in waratah bracts is the visible manifestation of oxidative damage to cell components, following chronic photoinhibition. Light-induced oxidative damage can lead to yellowing and pigment bleaching, lipid peroxidation, the development of necrotic lesions and senescence. However, lipid peroxidation as measured by the malionaldehyde assay gave no indication of oxidative damage to waratah bract tissue. This was probably due to the presence of anthocyanins and other flavonoids and sugars other than sucrose in bract tissue interfering with the colourimetric measurement of thiobarbituric acid reactive substances. The extensive planting of waratahs in NSW in the last five years suggests that the total value of lost production due to bract browning is likely to increase in the future. The browning disorder may also prevent the establishment of waratahs in other markets, as international cut-flower markets demand high quality blooms free from blemishes. The results of this study show that bract browning, photoinhibition and pigment loss are minimised by protecting waratahs from high light intensities from bud opening until harvest. However, the consequences of shading waratahs throughout the year require further investigation, as does the use of different percentages of shade cloth or other methods to reduce incident light.

Made available in DSpace on 2014-06-11T19:30:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-26Bitstream added on 2014-06-13T21:01:17Z : No. of bitstreams: 1 carvalho_tb_dr_jabo.pdf: 519619 bytes, checksum: e4ba444d5a227e52fbabd17b5ed6684e (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Universidade Estadual Paulista (UNESP) / Alterações no ambiente aquático, provocadas por ações antrópicas no ambiente natural ou artificial, causam mudanças em fatores físicos (ex: luminosidade) que podem afetar o comportamento e a fisiologia dos peixes. Assim, foi testado o efeito da luminosidade sobre o comportamento agressivo, a hierarquia social, indicadores de estresse e os níveis de esteróides sexuais em ciclídeos. Para isso, foram realizados 4 experimentos. Experimento I: foi avaliada a influência da intensidade luminosa sobre a agressividade em juvenis de Geophagus proximus, Oreochromis niloticus e Pterophyllum scalare. Foram comparadas duplas submetidas a duas intensidades luminosas (253,56 ± 62,25 lx e 1.435,92 ± 481,40 lx). A maior luminosidade reduziu a agressividade em O. niloticus, aumentou em P. scalare e não afetou a de G. proximus. Observou-se também que o nível de agressividade em O. niloticus foi maior que em G. proximus, que, por sua vez, foi maior que P. scalare. Isso sugere que a intensidade luminosa modula diferentemente a interação de peixes sociais, podendo o mecanismo estar associado aos padrões de agressividade de cada espécie. Experimento II: foi testada a influência da intensidade luminosa sobre o comportamento agonístico e indicadores de estresse (taxa ventilatória e atividade da catalase) em fêmeas de Tilapia rendalli. Foram comparadas duas intensidades luminosas: menor (253,56 ± 62,25 lx) e maior (1.435,92 ± 481,40 lx) em condições social (dupla) e de isolamento. A menor luminosidade aumentou a freqüência de ataques na dupla e no dominante, mas não afetou a interação do submisso. A taxa ventilatória do animal isolado foi maior na menor intensidade de luz. Assim, conclui-se que a luminosidade afeta a agressividade e atua como um estressor em fêmeas de T. rendalli. No entanto, essa resposta estressora pode não funcionar como o mecanismo causador do efeito da... / Animals show behavioral and physiological changes due to variations of environmental physical factors. Thus, we compared the effect of luminosity on agonistic behaviour, hierarchy settlement, stress, and plasma sexual steroids levels in cichlids. Experiment I: we compared the effect of light intensity on agonistic behavior of pair juvenile cichlids Geophagus proximus, Oreochromis niloticus and Pterophyllum scalare under two light intensities ( minor: 253.56 ± 62.25 lx and major: 1435.92 ± 481.40 lx). Major light intensity reduced aggressiveness in O. niloticus; increased in P. scalare and did not affect agonistic interactions in G. proximus. In the 2 light conditions, the aggressiveness level in O. niloticus is higher than G. proximus and P. scalare. We concluded rising light intensity affects agonistic interaction in different way in the three fish species, and mechanism underlying this data could be related to specific agonistic profile. Experiment II: we tested the influence of light intensity on aggressive behavior and indicators of stress (ventilatory frequency and catalase activity) in adult females of Tilapia rendalli. A minor (253.56 ± 62.25 lx) and major (1435.92 ± 481.40 lx) light intensity were compared in social condition (pair) and isolation. The pair and winner exhibited higher agonistic interactions at major intensity group, but luminosity did not affect attacks in loser. The ventilatory frequency of isolated animal was higher in the minor light intensity. Thus, we concluded that the luminosity affects the aggressiveness and it is a stressor in females of T. rendalli. However, that stressful event can not be main causing mechanism of the light intensity on agonistic behavior effect. Experiment III: we evaluated the effect of the light intensity on social hierarchy settlement and indicators of stress (hematocrit and glycemia) in males of Oreochromis niloticus... (Complete abstract click electronic access below)