A diversidade de estruturas de captura de presas (tentáculos e braços orais) em medusas adultas está associada a diferentes mecanismos de captura e hábitos alimentares. O entendimento do desenvolvimento dessas estruturas pode esclarecer a mecânica da alimentação e, consequentemente, aumentar o conhecimento sobre as consequências tróficas dos recorrentes blooms de cifomedusas. No entanto poucos estudos descrevem o desenvolvimento inicial das estruturas de captura e sua interação com o ambiente fluido (i.e., número de Reynolds, Re). Em vista disso, o objetivo deste trabalho foi descrever os estágios de desenvolvimento em espécies de Rhizostomeae (Mastigias papua, Cassiopea sp., Cotylorhiza tuberculata, Catostylus townsendi, Catostylus mosaicus, Lychnorhiza lucerna, Phyllorhiza punctata e Rhopilema esculentum) e \"Semaeostomeae\" (Chrysaora plocamia e Aurelia cf. sp. 4), com foco na umbrela e nos braços orais (capítulo 1); testar a hipótese de que diferentes temperaturas durante o crescimento geram desenvolvimento diferenciado da umbrela e dos braços orais, que compensariam o efeito da camada limite sob baixas temperaturas (i.e., baixo Re) para o funcionamento efetivo dessas estruturas como filtros coletores (capítulo 2); caracterizar a distribuição da epiderme ciliada e os fluxos produzidos em éfiras e medusas jovens de Lychnorhiza lucerna, medir a espessura da camada de água que os cílios conseguem mover e calcular o Re em torno dos digitata coberto por cílios (capítulo 3). Para isso as éfiras foram submetidas a tratamentos específicos e fotografadas até completarem 35 dias de idade e foi filmado o transporte de partículas pela epiderme ciliar. Concluímos que a caracterização do desenvolvimento inicial de distintas linhagens de éfiras de Scyphozoa possibilitou o conhecimento da morfologia das medusas, i.e., de suas estruturas natatórias e alimentares, propiciando, assim o entendimento de suas funções. Por sua vez, cifomedusas se mostraram resilientes às variações de temperatura, exibindo um crescimento diferenciado que deve garantir a manutenção das funções das estruturas natatórias e alimentares. A epiderme ciliar está presente ao longo de toda a medusa e moveu uma camada de água de até 0,28 mm. O batimento ciliar colabora com o mecanismo alimentar com o transporte de partículas e atua na dinâmica de mecânica de fluidos por criar fluxos na mesma direção do fluxo gerado pelas contrações umbrelares, ajudando a diminuir o efeito da camada limite. Por fim, ressaltamos que este trabalho mostrou a relevância de se estudar conjuntamente o desenvolvimento morfológico, o comportamento e a mecânica de fluidos para se compreender de forma complementar os mecanismos subjacentes à ecologia alimentar de importantes predadores marinhos como as medusas de Scyphozoa / The diversity of prey capture structures (tentacles and oral arms) in adult jellyfish is associated with different capture mechanisms and feeding habits. The understanding of these structures development can clarify the feeding mechanics and, consequently, increase the knowledge about the trophic consequences of the recurrent jellyfish blooms. However, few studies describe the capture structures initial development and their interaction with the fluid environment (i.e., Reynolds number, Re). The objective of this work was to describe the development stages in Rhizostomeae (Mastigias papua, Cassiopea sp., Cotylorhiza tuberculata, Catostylus townsendi, Catostylus mosaicus, Lychnorhiza lucerna, Phyllorhiza punctate and Rhopilema esculentum) and \"Semaeostomeae\" (Chrysaora plocamia and Aurelia cf. sp. 4) species, focusing on the bell and oral arms (chapter 1); to test the hypothesis that different temperatures during growth generate a differentiated development of the bell and oral arms, which would compensate for the boundary layer effect under low temperatures (i.e., low Re) for the effective functioning of these structures as collector filters (Chapter 2); to characterize the distribution of the ciliated epidermis and the flows produced in ephyrae and young jellyfish of Lychnorhiza lucerna, to measure the water layer thickness that the cilia can move and to calculate the Re around the digitata covered by cilia (Chapter 3). For this, the ephyrae were submitted to specific treatments and photographed until they were 35 days old and the transport of particles through the ciliary epidermis was filmed. We conclude that the initial development characterization of different strains of Scyphozoa ephyrae makes it possible to know the morphology of jellyfish, i.e., their swimming and feeding structures, thus providing an understanding of their functions. On the other hand, scyphomedusa showed to be resilient to the temperature variations, exhibiting a differentiated growth that must guarantee the maintenance of the swimming and food structures functions. The ciliary epidermis is present throughout the jellyfish and has moved a layer of water up to 0.28 mm. The ciliary stroke collaborates with the food mechanism with the transport of particles and acts on the dynamics of fluid mechanics by creating flows in the same direction of the flow generated by the bell contractions, helping to diminish the effect of the boundary layer. Finally, we highlight that this work showed the relevance of jointly studying the morphological development, behavior and fluid mechanics to comprehend in a complementary way the mechanisms underlying the food ecology of important marine predators such as Scyphozoa jellyfish

A filogenia dos diferentes grupos de Cnidaria permanece de certa forma pouco resolvida, uma vez que não há um consenso de quais são as relações entre as diferentes classes e ordens que compõem o filo. A espermiotaxonomia vem sendo utilizada como critério filogenético em diversos grupos de Metazoa. Para Cnidaria são poucos os trabalhos descrevendo a morfologia do sistema reprodutor masculino e do espermatozoide em nível de microscopia de luz e de microscopia eletrônica de transmissão. Exemplares das espécies Tamoya haplonema e Chiropsalmus quadrumanus (Cubozoa), Lychnorhiza lucerna e Chrysaora lactea (Scyphozoa), foram coletados próximos ao Centro de Biologia Marinha da Universidade de São Paulo e junto às bases do Instituto Oceanográfico da USP (Base de Cananéia e Base de Ubatuba) nos meses de agosto a outubro de 2014 e de abril a junho de 2015. Amostras das espécies Carukia barnesi, Chironex fleckeri e Chiropsella bronzie (Cubozoa) e Cassiopea sp. (Scyphozoa) foram coletadas ao longo da costa leste australiana de março a maio de 2016. Para a descrição histológica e histoquímica da gônada masculina, amostras do tecido gonadal foram fixadas em paraformaldeído 4% preparado com água do local da coleta e tampão fosfato de sódio 0,2M por 24 horas e as amostras foram processadas de acordo com o protocolo para historesina. Fragmentos da gônada masculina foram fixados em solução Karnovsky modificado (glutaraldeído 2,5% e 0,08% de paraformaldeído em tampão cacodilato de sódio 0,1 M, pH 7,4) e solução de Glutaraldeído (2.5% glutaraldeido em tampão cacodilato de sódio 0.1M em água do mar filtrada a vácuo, pH 7.2-7.4). Em seguida as amostras foram processadas de acordo com protocolo de microscopia eletrônica transmissão. Na presente dissertação é descrito de forma comparada o processo de espermatogênese dos cubozoários T. haplonema e C. quadrumanus através da histologia e histoquímica evidenciando o ciclo gonadal de ambos (capítulo 1). Descreve-se a espermatogênese e morfologia do espermatozoide, através da microscopia de luz e ultraestrutura para as espécies de Cubozoa T. haplonema, C. quadrumanus, Carukia barnesi, Chironex fleckeri e Chiropsella bronzie (Capítulo 2). Para as espécies de Scyphozoa Lychnorhiza lucerna, Chrysaora lactea e Cassiopea sp. descreve-se o processo de espermatogênese através da microscopia de luz e da microscopia eletrônica de transmissão, além do aspecto macroscópico da gônada masculina (Capítulo 3). Adicionalmente, nas considerações finais, é ressaltada a morfologia comparada dos espermatozoides de todas as espécies aqui estudadas evidenciando possíveis características únicas de cada classe, enumerando eventuais caracteres diagnósticos dos espermatozoides das espécies estudadas (Capítulo 4) / The phylogeny of the different groups of cnidarians remains elusive, since there is no consensus of what are the relationships between the different classes and orders that comprise the phylum. The spermiotaxonomy has been used as phylogenetic criteria in different groups of Metazoa. For Cnidaria there are few studies describing the morphology of the male reproductive system and sperm at the level of light microscopy and transmission electron microscopy. Specimens of the species Tamoya haplonema and Chiropsalmus quadrumanus (Cubozoa), Lychnorhiza lucerna and Chrysaora lactea (Scyphozoa), were collected near the Marine Biology Center of the University of São Paulo and near the bases of the Oceanographic Institute of USP (Cananéia and Ubatuba Bases) from August to October 2014 and from April to June 2015. Samples of the species Carukia barnesi, Chironex fleckeri and Chiropsella bronzie (Cubozoa) and Cassiopea sp. (Scyphozoa), were collected along the Australian east coast from March to May 2016. For histological and histochemistry description of the male gonads, samples were fixed in 4% paraformaldehyde prepared with water from the collection site and sodium phosphate buffer 0.2M for 24 hours. After that, the samples were processed following the protocol for historesin. Fragments of male gonads were fixed in modified Karnovsky solution (2.5% glutaraldehyde and 0.08% paraformaldehyde in 0.1 M sodium cacodylate buffer, pH 7.4) and glutaraldehyde (2.5% glutaraldehyde in cacodylate buffer 0.1M sodium in seawater vacuum Millipore filtered, pH 7.2-7.4). Then the samples were processed according to transmission electronic microscopy protocol. In this dissertation it is described the comparative spermatogenesis of the cubozoans T. haplonema and C. quadrumanus, under histology and histochemistry, showing the gonadal cycle (Chapter 1). We also describe the spermatogenesis and sperm morphology, under light microscopy and ultrastructure, for the Cubozoa species T. haplonema, C. quadrumanus, Carukia barnesi, Chironex fleckeri and Chiropsella bronzie (Chapter 2). For the Scyphozoa species, Lychnorhiza lucerna, Chrysaora lactea and Cassiopea sp., we describe the spermatogenesis process, under light transmission electronic microscopy, describing the macroscopic structure of the male gonad (Chapter 3). Additionally, in the final chapter, it is highlighted the comparative morphology of sperm of all species studied, evidencing possible unique features of each class, enumerating possible sperm characters (Chapter 4)

A filogenia dos diferentes grupos de Cnidaria permanece de certa forma pouco resolvida, uma vez que não há um consenso de quais são as relações entre as diferentes classes e ordens que compõem o filo. A espermiotaxonomia vem sendo utilizada como critério filogenético em diversos grupos de Metazoa. Para Cnidaria são poucos os trabalhos descrevendo a morfologia do sistema reprodutor masculino e do espermatozoide em nível de microscopia de luz e de microscopia eletrônica de transmissão. Exemplares das espécies Tamoya haplonema e Chiropsalmus quadrumanus (Cubozoa), Lychnorhiza lucerna e Chrysaora lactea (Scyphozoa), foram coletados próximos ao Centro de Biologia Marinha da Universidade de São Paulo e junto às bases do Instituto Oceanográfico da USP (Base de Cananéia e Base de Ubatuba) nos meses de agosto a outubro de 2014 e de abril a junho de 2015. Amostras das espécies Carukia barnesi, Chironex fleckeri e Chiropsella bronzie (Cubozoa) e Cassiopea sp. (Scyphozoa) foram coletadas ao longo da costa leste australiana de março a maio de 2016. Para a descrição histológica e histoquímica da gônada masculina, amostras do tecido gonadal foram fixadas em paraformaldeído 4% preparado com água do local da coleta e tampão fosfato de sódio 0,2M por 24 horas e as amostras foram processadas de acordo com o protocolo para historesina. Fragmentos da gônada masculina foram fixados em solução Karnovsky modificado (glutaraldeído 2,5% e 0,08% de paraformaldeído em tampão cacodilato de sódio 0,1 M, pH 7,4) e solução de Glutaraldeído (2.5% glutaraldeido em tampão cacodilato de sódio 0.1M em água do mar filtrada a vácuo, pH 7.2-7.4). Em seguida as amostras foram processadas de acordo com protocolo de microscopia eletrônica transmissão. Na presente dissertação é descrito de forma comparada o processo de espermatogênese dos cubozoários T. haplonema e C. quadrumanus através da histologia e histoquímica evidenciando o ciclo gonadal de ambos (capítulo 1). Descreve-se a espermatogênese e morfologia do espermatozoide, através da microscopia de luz e ultraestrutura para as espécies de Cubozoa T. haplonema, C. quadrumanus, Carukia barnesi, Chironex fleckeri e Chiropsella bronzie (Capítulo 2). Para as espécies de Scyphozoa Lychnorhiza lucerna, Chrysaora lactea e Cassiopea sp. descreve-se o processo de espermatogênese através da microscopia de luz e da microscopia eletrônica de transmissão, além do aspecto macroscópico da gônada masculina (Capítulo 3). Adicionalmente, nas considerações finais, é ressaltada a morfologia comparada dos espermatozoides de todas as espécies aqui estudadas evidenciando possíveis características únicas de cada classe, enumerando eventuais caracteres diagnósticos dos espermatozoides das espécies estudadas (Capítulo 4) / The phylogeny of the different groups of cnidarians remains elusive, since there is no consensus of what are the relationships between the different classes and orders that comprise the phylum. The spermiotaxonomy has been used as phylogenetic criteria in different groups of Metazoa. For Cnidaria there are few studies describing the morphology of the male reproductive system and sperm at the level of light microscopy and transmission electron microscopy. Specimens of the species Tamoya haplonema and Chiropsalmus quadrumanus (Cubozoa), Lychnorhiza lucerna and Chrysaora lactea (Scyphozoa), were collected near the Marine Biology Center of the University of São Paulo and near the bases of the Oceanographic Institute of USP (Cananéia and Ubatuba Bases) from August to October 2014 and from April to June 2015. Samples of the species Carukia barnesi, Chironex fleckeri and Chiropsella bronzie (Cubozoa) and Cassiopea sp. (Scyphozoa), were collected along the Australian east coast from March to May 2016. For histological and histochemistry description of the male gonads, samples were fixed in 4% paraformaldehyde prepared with water from the collection site and sodium phosphate buffer 0.2M for 24 hours. After that, the samples were processed following the protocol for historesin. Fragments of male gonads were fixed in modified Karnovsky solution (2.5% glutaraldehyde and 0.08% paraformaldehyde in 0.1 M sodium cacodylate buffer, pH 7.4) and glutaraldehyde (2.5% glutaraldehyde in cacodylate buffer 0.1M sodium in seawater vacuum Millipore filtered, pH 7.2-7.4). Then the samples were processed according to transmission electronic microscopy protocol. In this dissertation it is described the comparative spermatogenesis of the cubozoans T. haplonema and C. quadrumanus, under histology and histochemistry, showing the gonadal cycle (Chapter 1). We also describe the spermatogenesis and sperm morphology, under light microscopy and ultrastructure, for the Cubozoa species T. haplonema, C. quadrumanus, Carukia barnesi, Chironex fleckeri and Chiropsella bronzie (Chapter 2). For the Scyphozoa species, Lychnorhiza lucerna, Chrysaora lactea and Cassiopea sp., we describe the spermatogenesis process, under light transmission electronic microscopy, describing the macroscopic structure of the male gonad (Chapter 3). Additionally, in the final chapter, it is highlighted the comparative morphology of sperm of all species studied, evidencing possible unique features of each class, enumerating possible sperm characters (Chapter 4)

This research focused on population dynamics of two gelatinous zooplankters (Aequorea & Pyrosoma atlanticum) in the northern California Current to assess their relationship to environmental conditions and role in the pelagic ecosystem. Data collected since 1999 showed seasonal and interannual fluctuations in the abundance and distribution of Aequorea in the NCC, with a positive correlation with sea surface temperature and salinity. Pyrosoma atlanticum, which are typically found in tropical waters, have only been observed in high abundances in the NCC since 2014 and their role in the pelagic ecosystem is not well understood. Pyrosome abundance related to in situ environmental variables showed a positive correlation with warmer SST. We also used fatty acids as trophic markers to better understand pyrosome trophic ecology in the NCC. FA biomarkers suggest that pyrosomes have a broad phytoplankton diet, which may indicate an ability to inhabit warmer, lower nutrient zones. / 2020-01-11

Jellyfish have inhabited this planet for millions of years and are the oldest known metazoans that swim using muscles. They are found in freshwater sources and in oceans all over the world. Over millions of years of evolution, they have adapted to survive in a given environment. They are considered as one of the most energy efficient swimmers. Owing to these characteristics, jellyfish has attracted a lot of attention for developing energy efficient unmanned undersea vehicles (UUVs). The goal of this thesis is to provide understanding of the different physical mechanisms that jellyfish employs to achieve efficient swimming by using analytical and computational models. The models were validated by using the experimental data from literature. Based upon these models refinements and changes to engineering vehicles was proposed that could lead to significant enhancement in propulsion efficiency. In addition to the propulsion, the thesis addresses the practical aspects of deploying a jellyfish-inspired robotic vehicle by providing insights into buoyancy control and energy generation. The thesis is structured in a manner such that propulsive and structural models inspired from the natural animal were systematically combined with the practical aspects related to ionic diffusion driven buoyancy control system and thermal -- magnetic energy harvesting system. Jellyfish morphology, swimming mechanism and muscle architecture were critically reviewed to accurately describe the natural behavior and material properties. We provide full understanding of mesoglea, which plays most significant role towards swimming performance, in terms of composition, mechanical properties and nonlinear dynamics. Different jellyfish species exhibit different microstructure of mesoglea and thus there is a wide variety of soft materials. Mechanical properties of collagen fibers that form the main constituent toward imparting elasticity to mesoglea were reviewed and analyzed. The thesis discusses the theoretical models describing the role of structure of mesoglea towards its mechanical properties and explains the variation occurring in stiffness under given experimental environment. Muscle architecture found in jellyfish, nerve nets and its interconnection with the muscles were investigated to develop comprehensive understanding of jellyfish propulsion and its reaction to external stimuli. Different muscle arrangements were studied including radial, coronal muscle, and coronal-muscles-with-breaks in-between them as observed in Cyanea capillata. We modeled these muscle arrangements through finite element modeling (FEM) to determine their deformation and stroke characteristics and their overall role in bell contraction. We found that location and arrangement of coronal muscle rings plays an important role in determining their efficient utilization. Once the understanding of natural jellyfish was achieved, we translated the findings onto artificial jellyfish vehicle designed using Bio-inspired Shape Memory Alloy Composite (BISMAC) actuators. Detailed structural modeling was conducted to demonstrate deformation similar to that of jellyfish bell. FEM model incorporated hyperelastic behavior of artificial mesoglea (Ecoflex-0010 RTV, room temperature vulcanizing silicone with shore hardness (0010)), experimentally measured SMA temperature transformation, gravity and buoyancy forces. The model uses the actual control cycle that was optimized for driving the artificial jellyfish vehicle "robojelly". Using a comparative analysis approach, fundamental understanding of the jellyfish bell deformation, thrust generation, and mechanical efficiency were provided. Meeting energy needs of artificial vehicle is of prime importance for the UUVs. Some jellyfish species are known to use photosynthesis process indirectly by growing algae on their exumbrella and thereby utilizing the sunlight to generate energy. Inspired by this concept, an extensive model was developed for harvesting solar energy in underwater environment from the jellyfish bell structure. Three different species were modeled for solar energy harvesting, namely A.aurita, C.capillata and Mastigia sp., using the amorphous silicon solar cell and taking into account effect of fineness ratio, bell diameter, turbidity, depth in water and incidence angle. The models shows that in shallow water with low turbidity a large diameter vehicle may actually generate enough energy as required for meeting the demand of low duty cycle propulsion. In future, when the solar energy harvesting technology based upon artificial photosynthesis, referred to as "dye-sensitized solar cells", matures the model presented here can be easily extended to determine its performance in underwater conditions. In order to supplement the energy demand, a novel concept of thermal -- magnetic energy harvesting was developed and extensively modeled. The proposed harvester design allows capturing of even small temperature differences which are difficult for the thermoelectrics.  A systematic step-by-step model of thermo-magnetic energy harvester was presented and validated against the experimental data available in literature. The multi-physics model incorporates heat transfer, magnetostatic forces, mechanical vibrations, interface contact behavior, and piezoelectric based energy converter. We estimated natural frequency of the harvester, operating temperature regimes, and electromechanical efficiency as a function of dimensional and physical variables. The model provided limit cycle operation regimes which can be tuned using physical variables to meet the specific environment. Buoyancy control is used in aquatic animals in order to maintain their vertical trajectory and travel in water column with minimum energy expense. Some crustaceans employ selective ion replacement of heavy or lighter ions in their dorsal carapace. A model of a buoyancy chamber was developed to achieve similar buoyancy control using electro-osmosis. The model captures all the essential ionic transport and electrochemistry to provide practical operating cycle for the buoyancy engine in the ocean environment. / Ph. D.

This thesis presents the design and development of a novel biomimetic jellyfish robot that features ionic polymer metal composite actuators. The shape and swimming style of this underwater vehicle are based on oblate jellyfish species, which are known for their high locomotive efficiency. Ionic polymer metal composites (IPMC) are used as actuators in order to contract the bell and thus propel the jellyfish robot. This research focuses on translating the evolutionary successes of the natural species into a jellyfish robot that mimics the geometry, the swimming style, and the bell deformation cycle of the natural species. Key advantages of using IPMC actuators over other forms of smart material include their ability to exhibit high strain response due to a low voltage input and their ability to act as artificial muscles in water environment. This research specifically seeks to implement IPMC actuators in a biomimetic design and overcome two main limitations of these actuators: slow response rate and the material low blocking force. The approach presented in this document is based on a combination of two main methods, first by optimizing the performance of the IPMC actuators and second by optimizing the design to fit the properties of the actuators by studying various oblate species. Ionic polymer metal composites consist of a semi-permeable membrane bounded by two conductive, high surface area electrode. The IPMCs are manufactured is several variations using the Direct Assembly Process (DAP), where the electrode architecture is controlled to optimize the strain and stiffness of the actuators. The resulting optimized actuators demonstrate peak to peak strains of 0.8 % in air and 0.7 % in water across a frequency range of 0.1-1.0 Hz and voltage amplitude of 2 V. A study of different oblate species is conducted in order to attain a model system that best fits the properties of the IPMC actuators. The Aequorea victoria is chosen based on its bell morphology and kinematic properties that match the mechanical properties of the IPMC actuators. This medusa is characterized by it low swimming frequency, small bell deformation during the contraction phase, and high Froude efficiency. The bell morphology and kinematics of the Aequorea victoria are studied through the computation of the radius of curvature and thus the strain energy stored in the during the contraction phase. The results demonstrate that the Aequorea victoria stores lower strain energy compared to the other candidate species during the contraction phase. Three consecutive jellyfish robots have been built for this research project. The first generation served as a proof of concept and swam vertically at a speed of 2.2 mm/s and consumed 3.2 W of power. The second generation mimicked the geometry and swimming style of the Aurelia aurita. By tailoring the applied voltage waveform and the flexibility of the bell, the robot swam at an average speed of 1.5 mm/s and consumed 3.5 W of power. The third and final generation mimicked the morphology, swimming behavior, and bell kinematics of the Aequorea victoria. The resulting robot, swam at an average speed of 0.77 mm/s and consumed 0.7 W of power when four actuators are used while it achieved 1.5 mm/s and 1.1 W of power consumption when eight actuators are used. Key parameter including the type of the waveform, the geometry of the bell, and position and size of the IPMC actuators are identified. These parameters can be hit later in order to further optimize the design of an IPMC based jellyfish robot. / Master of Science

Bleaching is defined as the disruption of the symbiotic relationship between the host and Symbiodinium dinoflagellates, resulting in the exposure of the calcium carbonate skeleton. This phenomenon has been mostly linked to seawater temperature elevation. Bleaching events are becoming more intense and frequent, harming coral reefs around the world and affecting almost 100% of the community in some places. Therefore, it is important to understand if the effects of these recurrent stress events are cumulative on this photosymbiotic relationship. We experimentally tested how the Symbiodinium-associated jellyfish Cassiopea andromeda is affected by three consecutive thermal stress events, monitoring bell size and chlorophyll-a concentration. Jellyfishes in four physiological conditions regarding feeding frequency (daily and every three days) and Symbiodinium concentration (low and high) were subject to a one-week thermal stress at each experimental round. Three treatments were applied: 27ºC (control, maintained in this temperature during all experiment), 30ºC and 33ºC. After a three-week recovery period at 27ºC, thermal stress events were applied on two more instances intertwined by a recovery period. C. andromeda bleached and its chlorophyll-a content decreased for all temperatures during the first thermal stress and only at 33ºC for the second and third events. Size was only affected by feeding and by the second thermal stress. Higher food offer caused organisms to increase in size while those offered food with lower frequency shrunk. As observed in other hosts, high Symbiodinium concentration resulted in loss of chlorophyll-a, probably due to excessive production of reactive oxygen species and self-shading. C. andromeda jellyfish bleached just in the first stress event and its resilience to multiple thermal stresses is dependent upon biotic and abiotic factors. There was no difference in mortality in any condition or temperature applied. Feeding plays a crucial role on size and symbiotic dependency under thermal stress. Symbiodinium concentration is an important factor in experiments testing climate change scenarios and although symbiont concentration has no relation to the growth of the host, it affects the Symbiodinium itself, thus might be considered in future experiments. Chronic effects of multiple thermal stresses were observed for chlorophyll-a, while these were acute for growth. C. andromeda apparently does not rely only on Symbiodinium, especially under stressful conditions and can be used as a model to investigate the effects of climate change in Symbiodinium symbiosis. Without major host mortality, the behavior of Symbiodinium in its physiological limits after every single bleaching event can be monitored. / O branqueamento é definido pela ruptura da relação simbiótica entre o hospedeiro e o dinoflagelado Symbiodinium, resultando na exposição do esqueleto de carbonato de cálcio do hospedeiro, e tem sido associado principalmente à elevação da temperatura da água do mar. Esses eventos estão se tornando mais intensos e frequentes, prejudicando recifes de corais ao redor do mundo, resultando em branqueamento de quase 100% da comunidade em alguns locais. Portanto, é importante entender se os efeitos desses eventos de estresse são cumulativos neste relacionamento fotossimbiótico. No presente estudo foi experimentalmente testado como medusas de Cassiopea andromeda em simbiose com Symbiodinium são afetadas por três eventos consecutivos de estresse térmico, monitorando o tamanho da umbrella e a concentração de clorofila-a. Medusas em quatro condições fisiológicas em relação à frequência de aporte heterotrófico (diário e a cada três dias) e a concentração de Symbiodinium (baixa e alta) foram sujeitas a um estresse térmico de uma semana em cada rodada experimental. Foram aplicados três tratamentos: 27ºC (controle, mantido nesta temperatura durante todo o experimento), 30ºC e 33ºC. Após um período de recuperação de três semanas a 27ºC, os eventos de estresse térmico foram aplicados em mais duas instâncias interligadas por um período de recuperação. C. andromeda branqueou e sua clorofila-a diminuiu para todas as temperaturas durante o primeiro estresse térmico e apenas a 33ºC para o segundo e terceiro eventos. O tamanho só foi afetado pela alimentação e pelo segundo estresse térmico. A oferta de alimento mais frequente fez com que os organismos aumentassem de tamanho, enquanto aqueles aos quais se oferecia com uma menor frequência, diminuíram de tamanho. Conforme observado em outros hospedeiros, a alta concentração de Symbiodinium resultou em perda de clorofila-a, provavelmente devido à produção excessiva de espécies reativas de oxigênio e auto-sombreamento. Medusas de C. andromeda branquearam apenas no primeiro evento de estresse e sua resiliência a múltiplos estresses térmicos depende de condições bióticas e abióticas. Não houve diferença na mortalidade em qualquer condição ou temperatura aplicada. Sob condições de estresse térmico, o aporte heterotrófico desempenha um papel crucial no tamanho e dependência da simbiose. A concentração de Symbiodinium é um fator importante nos experimentos que utilizam cenários de mudanças climáticas. Embora a concentração de simbiontes não tenha relação com o crescimento do hospedeiro, isso afeta o próprio Symbiodinium e, portanto, deve ser considerado em futuros experimentos. Efeitos crônicos de múltiplos estresses térmicos foram observados para a clorofila-a, enquanto estes são agudos para o crescimento. C. andromeda aparentemente não depende do Symbiodinium, especialmente sob condições estressantes e pode ser usado como modelo para investigar os efeitos das alterações climáticas no Symbiodinium em simbiose. Sem maior mortalidade do hospedeiro, o comportamento do Symbiodinium pode ser monitorado até seus limites fisiológicos após cada evento de branqueamento.

Bleaching is defined as the disruption of the symbiotic relationship between the host and Symbiodinium dinoflagellates, resulting in the exposure of the calcium carbonate skeleton. This phenomenon has been mostly linked to seawater temperature elevation. Bleaching events are becoming more intense and frequent, harming coral reefs around the world and affecting almost 100% of the community in some places. Therefore, it is important to understand if the effects of these recurrent stress events are cumulative on this photosymbiotic relationship. We experimentally tested how the Symbiodinium-associated jellyfish Cassiopea andromeda is affected by three consecutive thermal stress events, monitoring bell size and chlorophyll-a concentration. Jellyfishes in four physiological conditions regarding feeding frequency (daily and every three days) and Symbiodinium concentration (low and high) were subject to a one-week thermal stress at each experimental round. Three treatments were applied: 27ºC (control, maintained in this temperature during all experiment), 30ºC and 33ºC. After a three-week recovery period at 27ºC, thermal stress events were applied on two more instances intertwined by a recovery period. C. andromeda bleached and its chlorophyll-a content decreased for all temperatures during the first thermal stress and only at 33ºC for the second and third events. Size was only affected by feeding and by the second thermal stress. Higher food offer caused organisms to increase in size while those offered food with lower frequency shrunk. As observed in other hosts, high Symbiodinium concentration resulted in loss of chlorophyll-a, probably due to excessive production of reactive oxygen species and self-shading. C. andromeda jellyfish bleached just in the first stress event and its resilience to multiple thermal stresses is dependent upon biotic and abiotic factors. There was no difference in mortality in any condition or temperature applied. Feeding plays a crucial role on size and symbiotic dependency under thermal stress. Symbiodinium concentration is an important factor in experiments testing climate change scenarios and although symbiont concentration has no relation to the growth of the host, it affects the Symbiodinium itself, thus might be considered in future experiments. Chronic effects of multiple thermal stresses were observed for chlorophyll-a, while these were acute for growth. C. andromeda apparently does not rely only on Symbiodinium, especially under stressful conditions and can be used as a model to investigate the effects of climate change in Symbiodinium symbiosis. Without major host mortality, the behavior of Symbiodinium in its physiological limits after every single bleaching event can be monitored. / O branqueamento é definido pela ruptura da relação simbiótica entre o hospedeiro e o dinoflagelado Symbiodinium, resultando na exposição do esqueleto de carbonato de cálcio do hospedeiro, e tem sido associado principalmente à elevação da temperatura da água do mar. Esses eventos estão se tornando mais intensos e frequentes, prejudicando recifes de corais ao redor do mundo, resultando em branqueamento de quase 100% da comunidade em alguns locais. Portanto, é importante entender se os efeitos desses eventos de estresse são cumulativos neste relacionamento fotossimbiótico. No presente estudo foi experimentalmente testado como medusas de Cassiopea andromeda em simbiose com Symbiodinium são afetadas por três eventos consecutivos de estresse térmico, monitorando o tamanho da umbrella e a concentração de clorofila-a. Medusas em quatro condições fisiológicas em relação à frequência de aporte heterotrófico (diário e a cada três dias) e a concentração de Symbiodinium (baixa e alta) foram sujeitas a um estresse térmico de uma semana em cada rodada experimental. Foram aplicados três tratamentos: 27ºC (controle, mantido nesta temperatura durante todo o experimento), 30ºC e 33ºC. Após um período de recuperação de três semanas a 27ºC, os eventos de estresse térmico foram aplicados em mais duas instâncias interligadas por um período de recuperação. C. andromeda branqueou e sua clorofila-a diminuiu para todas as temperaturas durante o primeiro estresse térmico e apenas a 33ºC para o segundo e terceiro eventos. O tamanho só foi afetado pela alimentação e pelo segundo estresse térmico. A oferta de alimento mais frequente fez com que os organismos aumentassem de tamanho, enquanto aqueles aos quais se oferecia com uma menor frequência, diminuíram de tamanho. Conforme observado em outros hospedeiros, a alta concentração de Symbiodinium resultou em perda de clorofila-a, provavelmente devido à produção excessiva de espécies reativas de oxigênio e auto-sombreamento. Medusas de C. andromeda branquearam apenas no primeiro evento de estresse e sua resiliência a múltiplos estresses térmicos depende de condições bióticas e abióticas. Não houve diferença na mortalidade em qualquer condição ou temperatura aplicada. Sob condições de estresse térmico, o aporte heterotrófico desempenha um papel crucial no tamanho e dependência da simbiose. A concentração de Symbiodinium é um fator importante nos experimentos que utilizam cenários de mudanças climáticas. Embora a concentração de simbiontes não tenha relação com o crescimento do hospedeiro, isso afeta o próprio Symbiodinium e, portanto, deve ser considerado em futuros experimentos. Efeitos crônicos de múltiplos estresses térmicos foram observados para a clorofila-a, enquanto estes são agudos para o crescimento. C. andromeda aparentemente não depende do Symbiodinium, especialmente sob condições estressantes e pode ser usado como modelo para investigar os efeitos das alterações climáticas no Symbiodinium em simbiose. Sem maior mortalidade do hospedeiro, o comportamento do Symbiodinium pode ser monitorado até seus limites fisiológicos após cada evento de branqueamento.

This thesis presents an automatic animation system for jellyfish that is based on a physical simulation of the organism and its surrounding fluid. Our goal is to explore the unusual style of locomotion, namely jet propulsion, which is utilized by jellyfish. The organism achieves this propulsion by contracting its body, expelling water, and propelling itself forward. The organism then expands again to refill itself with water for a subsequent stroke. We endeavor to model the thrust achieved by the jellyfish, and also the evolution of the organism's geometric configuration. <p> We restrict our discussion of locomotion to fully grown adult jellyfish, and we restrict our study of locomotion to the resonant gait, which is the organism's most active mode of locomotion, and is characterized by a regular contraction rate that is near one of the creature's resonant frequencies. We also consider only species that are axially symmetric, and thus are able to reduce the dimensionality of our model. We can approximate the full 3D geometry of a jellyfish by simulating a 2D slice of the organism. This model reduction yields plausible results at a lower computational cost. From the 2D simulation, we extrapolate to a full 3D model. To prevent our extrapolated model from being artificially smooth, we give the final shape more variation by adding noise to the 3D geometry. This noise is inspired by empirical data of real jellyfish, and also by work with continuous noise functions from the graphics community. <p> Our 2D simulations are done numerically with ideas from the field of computational fluid dynamics. Specifically, we simulate the elastic volume of the jellyfish with a spring-mass system, and we simulate the surrounding fluid using the semi-Lagrangian method. To couple the particle-based elastic representation with the grid-based fluid representation, we use the immersed boundary method. We find this combination of methods to be a very efficient means of simulating the 2D slice with a minimal compromise in physical accuracy.

This thesis presents an automatic animation system for jellyfish that is based on a physical simulation of the organism and its surrounding fluid. Our goal is to explore the unusual style of locomotion, namely jet propulsion, which is utilized by jellyfish. The organism achieves this propulsion by contracting its body, expelling water, and propelling itself forward. The organism then expands again to refill itself with water for a subsequent stroke. We endeavor to model the thrust achieved by the jellyfish, and also the evolution of the organism's geometric configuration. <p> We restrict our discussion of locomotion to fully grown adult jellyfish, and we restrict our study of locomotion to the resonant gait, which is the organism's most active mode of locomotion, and is characterized by a regular contraction rate that is near one of the creature's resonant frequencies. We also consider only species that are axially symmetric, and thus are able to reduce the dimensionality of our model. We can approximate the full 3D geometry of a jellyfish by simulating a 2D slice of the organism. This model reduction yields plausible results at a lower computational cost. From the 2D simulation, we extrapolate to a full 3D model. To prevent our extrapolated model from being artificially smooth, we give the final shape more variation by adding noise to the 3D geometry. This noise is inspired by empirical data of real jellyfish, and also by work with continuous noise functions from the graphics community. <p> Our 2D simulations are done numerically with ideas from the field of computational fluid dynamics. Specifically, we simulate the elastic volume of the jellyfish with a spring-mass system, and we simulate the surrounding fluid using the semi-Lagrangian method. To couple the particle-based elastic representation with the grid-based fluid representation, we use the immersed boundary method. We find this combination of methods to be a very efficient means of simulating the 2D slice with a minimal compromise in physical accuracy.