Thesis (M.Tech.: Homoeopathy)-Dept. of Homoeopathy, Durban University of Technology, 2008. xiii, 159 leaves / The purpose of this study was to determine the effects of Gymnura natalensis in the thirtieth centesimal potency on healthy volunteers and to record the signs and symptoms produced by the volunteers during the study. These signs and symptoms determined the therapeutic indications of this remedy for its prescription according to the homoeopathic Law of Similars. A further aim of this study is a proposed group analysis of a natural family of biologically unrelated sea animal remedies (Mangialavori, 2002) with the aim of highlighting themes, similarities and differences within the group.

Mini-dissertation submitted in partial compliance with the requirements for the Master’s Degree in Technology: Homoeopathy in the Department of Homoeopathy at the Durban University of Technology, 2008. / The aim of this study was to determine the effect of Gymnura natalensis 30CH on healthy volunteers, and to record the signs and symptoms produced, so that it may be prescribed to those requiring it according to the Law of Similars. The other aims of this study were to compare the proving symptoms of Gymnura natalensis 30CH to the toxicology of stingray venom and to analyze the remedy picture in terms of the Doctrine of Signatures. It was hypothesised that the thirtieth centesimal potency of the remedy would produce clearly observable signs and symptoms in healthy volunteers (provers). It was further hypothesised that the above signs and symptoms would show a correlation to the toxicology of stingray venom and to the Doctrine of Signatures. The homoeopathic proving of Gymnura natalensis took the form a double-blind, randomised, placebo-controlled trial. The selected proving potency was the thirtieth centesimal potency. A total population of 30 suitable and consenting volunteers participated in this trial. Twenty percent of this population was randomly administered a placebo-control substance. The collection of data from the provers took the form of a journal which was kept by each prover in which their proving signs and symptoms were recorded over a period of five weeks after the administration of the remedy or placebo. On completion of the proving, each journal was assessed by the researcher to determine the suitability of the recorded symptoms for inclusion in the materia medica of Gymnura natalensis. These symptoms were then translated into the language of the materia medica and repertory and a remedy picture was then formulated. Data from case histories, physical examinations (Appendix D) and group discussions were also taken into account during the analysis of the proving the symptoms. A concurrent proving study of Gymnura natalensis, conducted by Naidoo (2008), focused on comparing the symptoms of this remedy to those of other existing remedies that were derived from the sea. A variety of mental, emotional and physical symptoms were extracted from the proving study of Gymnura natalensis. The main mental and emotional symptoms of the remedy included anxiety, irritability, depression, a feeling of disconnection, spaciness of the mind and dreams of events and incidents of the past. The characteristic physical symptoms obtained from the proving included headaches, a reduction of pre-menstrual symptoms, heart palpitations, skin eruptions on the back, low energy levels, tiredness and sleep abnormalities. Symptoms that showed a correlation to the toxicological symptoms of stingray envenomation included frequent urination, muscular cramps, heart palpitations, laboured breathing, fever and copious night sweats. The symptoms that characterised the remedy in terms of the Doctrine of Signatures included anxiety, instinctive behaviour, the desire to be alone, feelings of disconnection, detachment and isolation and skin eruptions on the back. The investigation confirmed the hypothesis that Gymnura natalensis would produce clearly observable sings and symptoms in healthy volunteers. The correlation of the proving symptoms to the toxicology of stingray venom and the Doctrine of Signatures provided a clarification of the remedy picture to assist in the understanding and prescription of this remedy.

Thesis (M.S.)--University of West Florida, 2008. / Title from title page of source document. Document formatted into pages; contains 0 pages. Includes bibliographical references.

Thirteen elasmobranch species were collected during a four year seine-net survey of the intertidal margins of Moreton Bay, a large subtropical embayment in southeast Queensland, Australia. The inshore elasmobranch fauna of Moreton Bay is relatively species rich in comparison to sites elsewhere in Australia, emphasising the regional importance of this ecosystem. Stingrays were the most common large predators in the intertidal, with overall catches dominated numerically by the blue-spotted maskray Neotrygon kuhlii (53.8%) and the estuary stingray Dasyatis fluviorum (22.2%). The biological and demographic characteristics of these two species were examined in detail. Neotrygon kuhlii ranged in size from 11.5 – 46.5 cm disc width (WD), with 50% maturity in females at 31.4 cm WD and 6.32 years old and at 29.4 cm WD and 3.95 years in males. Neotrygon kuhlii has a synchronous annual reproductive cycle, producing one litter of 1 – 3 pups (mean of 1.67 ± 0.71 S.D.) in the late Austral summer after a four month gestation. Maximum age estimates of 13 and 10 years were obtained from females and male N. kuhlii, respectively. Annual band pair deposition was confirmed through the recapture of four wild calcein-injected individuals from 22.7 to 30.2 cm WD. A three parameter power function provided the best statistical fit to age-at-size data for both sexes, providing parameter estimates of y0 = 163.13, a = 58.52 and b = 0.58 for females and y0 = 165.13, a = 59.02 and b = 0.54 in males. Individual growth rates obtained from tagged specimens were not qualitatively different to modelled growth predictions. Tagging studies produced a total recapture rate of 16.1%, with individual rays at liberty for up to 1081 days. Direct estimates of instantaneous mortality for N. kuhlii were derived by creating catch curves for both sexes from age-frequency keys. Mortality was estimated at 0.171 ± 0.024.yr-1 S.E. in females, corresponding with a population growth rate of 1.00.yr-1 based on deterministic matrix demographic model predictions, and 0.345 ± 0.022.yr-1 S.E. in males. Seven age-independent and two age-dependent indirect mortality estimates produced negative population growth rates of 0.84 to 0.98.yr-1. Elasticity results were relatively robust to mortality estimates, with juvenile survivorship contributing 74-75% of total elasticity under all scenarios. Dasyatis fluviorum is endemic to near-shore, estuarine and riverine habitats along the eastern coast of Australia. Previous records of the species from northern Australia and New Guinea appear to be misidentifications of other, similar species. Dasyatis fluviorum was caught at 15.5 cm to 76.2 cm WD in Moreton Bay, with 50% maturity occurring at 63 cm WD (13.40 years) in females and 41.2 cm WD (6.97 years) in males. Maximum age estimates of 21 and 16 years were obtained from females and males, respectively. The Gompertz growth function provided the best fit to estimated age data in female D. fluviorum, providing parameter estimates of WD∞ = 100.3 cm, k = 0.09.yr-1 and t0 = 5.66. The modified two-parameter von Bertalanffy growth function provided the best fit to male size-at-age data, providing parameter estimates of WD∞ = 73.4 cm, k = 0.10.yr-1 and b = 0.86. An annual reproductive cycle in female D. fluviorum was hypothesised based on preliminary reproductive data. Fecundity estimates were derived from the related D. americana for input into deterministic and stochastic demographic models. Six out of nine indirect mortality estimates produced positive population growth in deterministic models, with a probabilistic estimate of 1.02.yr-1. Elasticity results were robust to model structure, mortality and fecundity estimates, with juvenile survivorship comprising 74-78% of total elasticity under all scenarios. Both N. kuhlii and D. fluviorum provide interesting case studies in elasmobranch conservation. Neotrygon kuhlii is a common bycatch of demersal prawn-trawl fisheries in Australia. Although mandatory turtle exclusion devices (TEDs) exclude most large vertebrates from trawl catches in Australian waters, their benefits in the reduction of smaller elasmobranch bycatch has not been empirically tested. The results of deterministic demographic models show that TEDs can, in principle, mitigate the impacts of trawl fisheries by partially excluding highly-elastic large juvenile age-classes. However, N. kuhlii is the largest of the four Neotrygon species found in Australian waters and bycatch of the three smaller species may be less reduced by current bycatch reduction technologies. Dasyatis fluviorum is affected by a suite of anthropogenic threats in its near-shore and estuarine habitats including commercial and recreational fisheries, habitat modification and pollution. Within Moreton Bay, 10.8% of the surveyed population bore evidence of past interactions with fisheries as evidenced by retained hooks or mutilated tails. Deep-hooking resulted in significant pathological effects including fibrocollagenous scar tissue masses, peritonitis and hepatitis. Stochastic demographic scenarios were created to model the potential effects of low (0.02 yr-1), medium (0.05 yr-1) and high (0.10 yr-1) rates of additive anthropogenic mortality to simulate stage-specific conservation interventions on D. fluviorum. Removing anthropogenic mortality on juvenile age-classes provided the largest benefits in terms of reducing population decline. The probability of the species’ conservation status declining further to Endangered, based on IUCN criteria, ranged from 39% to 100% under these mortality scenarios if no conservation measures were applied.

Thirteen elasmobranch species were collected during a four year seine-net survey of the intertidal margins of Moreton Bay, a large subtropical embayment in southeast Queensland, Australia. The inshore elasmobranch fauna of Moreton Bay is relatively species rich in comparison to sites elsewhere in Australia, emphasising the regional importance of this ecosystem. Stingrays were the most common large predators in the intertidal, with overall catches dominated numerically by the blue-spotted maskray Neotrygon kuhlii (53.8%) and the estuary stingray Dasyatis fluviorum (22.2%). The biological and demographic characteristics of these two species were examined in detail. Neotrygon kuhlii ranged in size from 11.5 – 46.5 cm disc width (WD), with 50% maturity in females at 31.4 cm WD and 6.32 years old and at 29.4 cm WD and 3.95 years in males. Neotrygon kuhlii has a synchronous annual reproductive cycle, producing one litter of 1 – 3 pups (mean of 1.67 ± 0.71 S.D.) in the late Austral summer after a four month gestation. Maximum age estimates of 13 and 10 years were obtained from females and male N. kuhlii, respectively. Annual band pair deposition was confirmed through the recapture of four wild calcein-injected individuals from 22.7 to 30.2 cm WD. A three parameter power function provided the best statistical fit to age-at-size data for both sexes, providing parameter estimates of y0 = 163.13, a = 58.52 and b = 0.58 for females and y0 = 165.13, a = 59.02 and b = 0.54 in males. Individual growth rates obtained from tagged specimens were not qualitatively different to modelled growth predictions. Tagging studies produced a total recapture rate of 16.1%, with individual rays at liberty for up to 1081 days. Direct estimates of instantaneous mortality for N. kuhlii were derived by creating catch curves for both sexes from age-frequency keys. Mortality was estimated at 0.171 ± 0.024.yr-1 S.E. in females, corresponding with a population growth rate of 1.00.yr-1 based on deterministic matrix demographic model predictions, and 0.345 ± 0.022.yr-1 S.E. in males. Seven age-independent and two age-dependent indirect mortality estimates produced negative population growth rates of 0.84 to 0.98.yr-1. Elasticity results were relatively robust to mortality estimates, with juvenile survivorship contributing 74-75% of total elasticity under all scenarios. Dasyatis fluviorum is endemic to near-shore, estuarine and riverine habitats along the eastern coast of Australia. Previous records of the species from northern Australia and New Guinea appear to be misidentifications of other, similar species. Dasyatis fluviorum was caught at 15.5 cm to 76.2 cm WD in Moreton Bay, with 50% maturity occurring at 63 cm WD (13.40 years) in females and 41.2 cm WD (6.97 years) in males. Maximum age estimates of 21 and 16 years were obtained from females and males, respectively. The Gompertz growth function provided the best fit to estimated age data in female D. fluviorum, providing parameter estimates of WD∞ = 100.3 cm, k = 0.09.yr-1 and t0 = 5.66. The modified two-parameter von Bertalanffy growth function provided the best fit to male size-at-age data, providing parameter estimates of WD∞ = 73.4 cm, k = 0.10.yr-1 and b = 0.86. An annual reproductive cycle in female D. fluviorum was hypothesised based on preliminary reproductive data. Fecundity estimates were derived from the related D. americana for input into deterministic and stochastic demographic models. Six out of nine indirect mortality estimates produced positive population growth in deterministic models, with a probabilistic estimate of 1.02.yr-1. Elasticity results were robust to model structure, mortality and fecundity estimates, with juvenile survivorship comprising 74-78% of total elasticity under all scenarios. Both N. kuhlii and D. fluviorum provide interesting case studies in elasmobranch conservation. Neotrygon kuhlii is a common bycatch of demersal prawn-trawl fisheries in Australia. Although mandatory turtle exclusion devices (TEDs) exclude most large vertebrates from trawl catches in Australian waters, their benefits in the reduction of smaller elasmobranch bycatch has not been empirically tested. The results of deterministic demographic models show that TEDs can, in principle, mitigate the impacts of trawl fisheries by partially excluding highly-elastic large juvenile age-classes. However, N. kuhlii is the largest of the four Neotrygon species found in Australian waters and bycatch of the three smaller species may be less reduced by current bycatch reduction technologies. Dasyatis fluviorum is affected by a suite of anthropogenic threats in its near-shore and estuarine habitats including commercial and recreational fisheries, habitat modification and pollution. Within Moreton Bay, 10.8% of the surveyed population bore evidence of past interactions with fisheries as evidenced by retained hooks or mutilated tails. Deep-hooking resulted in significant pathological effects including fibrocollagenous scar tissue masses, peritonitis and hepatitis. Stochastic demographic scenarios were created to model the potential effects of low (0.02 yr-1), medium (0.05 yr-1) and high (0.10 yr-1) rates of additive anthropogenic mortality to simulate stage-specific conservation interventions on D. fluviorum. Removing anthropogenic mortality on juvenile age-classes provided the largest benefits in terms of reducing population decline. The probability of the species’ conservation status declining further to Endangered, based on IUCN criteria, ranged from 39% to 100% under these mortality scenarios if no conservation measures were applied.

Chondrichthyans are cartilaginous fishes that include the extant chimaeras, sharks, and batoids, and their extinct relatives. In this dissertation, I examined the growth, development, and relationships of extinct and extant chondrichthyans. I reexamined the skeleton of fossil and fetal specimens of the angel sharks (Squatiniformes) and reanalyzed the current morphologically based hypothesis of chondrichthyan evolution, which conflicts with the current molecular based hypothesis. I did this by including extinct taxa and new characters based on dentition, and the ethmoid, occipital, pectoral, and vertebral skeleton. My results supported the pre-existing morphological hypothesis that angel sharks, saw sharks, and batoids form a clade. However, some of my new characters, particularly those based on the vertebral morphology, indicate that fetal and juvenile angel sharks do not share as many apomorphies with batoids as previously hypothesized from the examination of adults. I also examine the relationships of major groups within batoids, beginning with the construction of a hypothesis of the evolutionary history of electric rays (Torpediniformes). My results are consistent with previous rank-based classifications. However, they deviate from previous classifications depending on the criteria used to generate the hypothesis and on which taxon, or combination of taxa, were used to root the ingroup phylogeny. Because pectoral and vertebral morphology are so critical to morphological hypotheses, I also examined the growth and development of the synarcual cartilage in batoid fishes, with particular emphasis on the synarcual of skates (Rajiformes). My results demonstrate that calcification and chondrification do not proceed in the same order, temporally and spatially. Finally, I redescribe the extinct batoid †Cyclobatis, known only from the Cretaceous, and evaluate its phylogenetic position. My results indicate that †Cyclobatis, the oldest known rajid, is also the sister taxon to a clade of all known extant members of Rajidae. Furthermore, the inclusion of new characters, mainly derived from the synarcual, help to resolve the interrelationships of Rajidae. / text

Crude oil causes both lethal and sublethal effects on marine organisms, but the impact upon sensory function remains unexplored. Elasmobranchs rely upon the effective functioning of their sensory systems for use in feeding, mating, and predator avoidance. The objective of this study was to test the effect of crude oil upon the olfactory and electroreceptive sensitivity of the Atlantic stingray, Dasyatis sabina. The magnitudes of the electro-olfactogram (EOG) responses were significantly depressed by 26% (Glutamic Acid) to 157% (Cysteine) for all amino acids when stingrays were exposed to crude oil. The shapes of the EOG responses when exposed to oil were also significantly different, exhibiting a more protracted response compared to un-exposed stingrays. Oil exposed stingrays exhibited a significant decrease in orientation distance to prey-simulating electric fields. This study is the first to quantify the effects of crude oil on olfactory and electrosensory sensitivity of marine predators. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2016. / FAU Electronic Theses and Dissertations Collection

Made available in DSpace on 2015-04-11T13:54:58Z (GMT). No. of bitstreams: 1 juliana luiza.pdf: 3875282 bytes, checksum: e88fed331ab492bec9b53ea5c76c15f5 (MD5) Previous issue date: 2013-05-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Accidents caused by freshwater stingrays are characterized by intense pain and pathological changes at the lesion site, which include edema, erythema and, in most cases, necrosis. In this study, mucus and tissue extracts from the dorsal region and sting of freshwater stingrays Potamotrygon motoro and Plesiotrygon iwamae were analyzed by electrophoresis on SDS-PAGE and zymography. The myotoxic activity (local and systemic) induced by extracts in murine model was evaluated by morphometric analysis and enzimatic activity of the phospholipase A2 (indirect hemolysis) in agarose gel. P. motorosting extract showed a diffuse band with 10 kDa, several between 58 and 27 kDa, and proteolytic components above 58 kDa, while the dorsal region extract showed a strong and diffuse band around 41 kDa and a proteolytic component with 6 kDa. P. iwamae showed, in all samples, a diffuse and intense band with 15 kDa and proteolytic components around 6 and 40 kDa. Doses of 140 μg of P. iwamae protein extracts (sting and dorsal region) induced indirect hemolysis after 24 and 48 hours, but the halo diameter was below 10 mm (minimum value set for the technical), showing a weak phospholipase A2activity. Coagulative necrosis of the muscle tissue, muscle fiber regeneration and inflammatory infiltrates, including neutrophils, macrophages and a reduced number of eosinophils and lymphocytes were observed 24 hours after injection of 400 μg of P. motoro and P. iwamae mucus extracts in mice gastrocnemius muscle. These results were also observed, in a lower proportion, in the gastrocnemius muscles of the contralateral legs, showing that extracts of both species were able to induce a systemic rhabdomyolysis when tested in BALB/c mice. / Acidentes por arraias de água doce são caracterizados por dor intensa e alterações patológicas no local da lesão, que incluem edema, eritema e, na maioria dos casos, necrose. Nesta pesquisa, os extratos de muco e tecido do dorso e do ferrão das arraias Plesiotrygon iwamae e Potamotrygon motoro foram analisados por eletroforese em SDS-PAGE e por zimografia. A atividade miotóxica (local e sistêmica) induzida pelos extratos, em modelo murino, foi avaliada por histopatologia e a atividade da enzima fosfolipase A2 (hemólise indireta), em gel de agarose. O extrato do ferrão de P. motoro apresentou uma banda difusa de 10 kDa, várias entre 58 e 27 kDa e componentes proteolíticos acima de 58 kDa, enquanto que o extrato do dorso apresentou uma banda forte difusa com cerca de 41 kDa e um componente proteolítico de 6 kDa. Em P. iwamae, todas as amostras apresentaram uma banda intensa e difusa de 15 kDa e componentes proteolíticos de 6 e 40 kDa. As doses de 140 μg de proteína dos extratos de P. iwamae induziram hemólise indireta nos intervalos de tempo de 24 e 48 horas, porém, não formaram o halo de 10 mm de diâmetro (valor mínimo definido para a técnica), demonstrando uma fraca atividade de fosfolipase A2. Necrose coagulativa do tecido muscular, regeneração das fibras musculares e presença de infiltrados inflamatórios, incluindo neutrófilos, macrófagos, e um número reduzido de eosinófilos e linfócitos foram observados 24 horas após a injeção da dose de 400 μg dos extratos de muco do dorso e do ferrão das arraias P. motoro e P. iwamae no músculo gastrocnêmio dos camundongos. Tais resultados também foram observados, em menor volume, nos músculos gastrocnêmios das patas contralaterais, demonstrando que os extratos das duas espécies foram capazes de induzir a uma rabdomiólise sistêmica quando testados em camundongos BALB/c.

We rely so much on vision that it is hard to imagine sensing the world differently. But most organisms primarily use other sensory information, even something as detached from our senses as electricity. Some fish, called weakly electric fish, generate electric pulses to sense their environment. Objects in their environment distort the electric pulses, and the fish use special receptors in their skin to process these distortions and identify the nearby objects. They detect the location, size, shape, and electric properties of nearby objects, enabling them to find preferred food. These fish use their discharges not only for sensing and foraging as described, but also for communication. Investigating this sensory system can provide insights into neural computations for sensory processing more broadly, and can expand our understanding of the complex stimuli present in our environment that we do not perceive.In the first half of this work, we investigated how the weakly electric fish Gnathonemus petersii processes the electric sensory information to interact with its environment. We also used the tools developed in this work to study social behavior in groups of freely swimming fish. Chapter 1 provides an in-depth introduction to this model organism and its prominent active electrolocation behavior. This introductory chapter is focused on the parts of the behavior that are relevant to the computational models developed in this work. We investigated the active electrolocation behavior using a comprehensive end-to-end model that contains multiple components, which will be detailed in the following chapters. Chapter 2 describes the physics model that simulates the fish and its environment to collect data. The physics model builds on previous work and extends it to a more general framework that can be used to simulate the fish in different environments. We developed and adequately documented an open code base that can be used to simulate various fish species and their interactions with nearby objects or electrical boundaries. Chapter 3, specifically Section 3.3, presents a data-based model of the electroreceptors that process the sensory input. We used machine learning techniques to develop a model that can predict the response of the receptors to distortions due to different objects. The model is based on local field potential data collected from the afferent layers of the electrosensory lobe, the first brain area that processes the sensory input. This data was collected by Abigail Zadina in Nathaniel Sawtell’s laboratory at Columbia University. Chapter 3, specifically Section 3.4, describes the neural network models that identify computations that help solve the behavior. We used data generated from the physics model as sensory input, we used our electroreceptor model to parse this data serving as first-stage input to down- stream brain areas, and we used neural network models to characterize the nearby objects’ spatial and electric properties based on the sensory input. Based on results from our neural network models, we set two hypotheses for how weakly electric fish sense their environment and motivate experiments on less studied brain areas to test these hypotheses. First, we suggest that decoding all spatial and electric properties of a nearby object distorting the electric discharge is very challenging due to interactions between these properties, but first decoding the spatial properties and then using the spatial properties as internal feedback to decode the electric properties helps solve the task by disentangling the interactions. Second, we suggest that the specialized Schnauzenorgan organ of the weakly electric G. petersii, previously described as an electric fovea due to the very high density of electroreceptors and believed to serve a primary role in close-range characterization, may also play a role in long-range detection of objects surrounding the fish. Chapter 4 explores social interactions in groups of freely swimming fish and starts to investigate how they use their electric discharges to navigate, interact and communicate. Here, we used our physics-based framework to accurately identify the fish that emitted each electric discharge in a group of fish. This work is currently in progress and we performed various preliminary analyses to investigate the social behavior and social rank of these fish, which we present here. Data for this project was collected by Federico Pedraja in Nathaniel Sawtell’s laboratory at Columbia University. The second half of this work addresses a variety of different research questions with loose connections in between them and in relation to the first half. The common factor present in all these projects can be generally described as investigating how computations may be used in neural circuits to produce successful behavior. We used a variety of computational models and tools to investigate these questions, and we present the results of these investigations in the following chapters. Chapter 5 provides a biologically plausible architecture alternative for the classical binary classification task. Typically, feed-forward models have been used to solve this task. However, neocortical circuits likely involved in decision making are recurrent and sparse. We used a recurrent neural network model with sparsity constraints to solve the binary classification task. We demonstrated that the sparse recurrent networks solve the task well, make use of dynamic computation similar to evidence accumulation, and distribute the information throughout the network despite the sparsity constraints. Chapter 6 explores syntactic differences of world languages and offers a potential neural computation mechanism that could account for those differences. We focused on differences in the basic word order of simple sentences because these have been extensively studied in the linguistic literature. These simple sentences only have three parts, subject, verb, and object, and the order of these parts varies across languages non-uniformly. We aimed to provide a possible language generation mechanism that could account for these differences. Chapter 7 investigates the computational journey from numerical cognition to arithmetic ability. This research direction was motivated by and based on experimental work that addressed whether bees (and later stingrays and cichlids) can learn simple arithmetic operations. This project was designed for introducing a Columbia SEAS undergraduate student, Katharyn Fatehi, to computational neuroscience research. I mentored Kat through the Women in Science at Columbia program, and provided detailed guidance, code base, tutorials and instructions for her to learn about computational neuroscience research and to contribute to this project. Chapter 8 represents my contribution to a large collaboration effort aimed at improving spike sorting techniques. This project quantified the impact on spike sorting quality of the geometry mis- match between typical recording probes (1D, or 2D at best) and the 3D structure of the brain. We leveraged the experimental setup, multi-electrode recording arrays with planar geometry recording the activity of 2D retinal tissue, to address this question. The work presented in this thesis is a collection of projects that investigate neural computations in different contexts. The first half of the work is focused on the weakly electric fish G. petersii and its active electrolocation behavior. The second half of the work explores a variety of different research questions related to computational mechanisms that could be implemented in neural circuits. The work presented here is a step towards understanding how computations in neural circuits can produce successful behavior in different contexts.

Made available in DSpace on 2015-04-22T22:17:31Z (GMT). No. of bitstreams: 1 DISSERTACAO - WALACE BATISTA.PDF: 1407845 bytes, checksum: f0b36df932039802563ad55fc19ae923 (MD5) Previous issue date: 2008-03-31 / Fundação de Amparo à Pesquisa do Estado do Amazonas / The fish as food is a major source of high-quality protein, with a balance of essential amino acids, and the quality of lipids, great source of polyunsaturated fatty acids. Over the years the fish has been the principal source of nutrients of animal origin in the Amazon and exploitation of fishery resources in a rational way is one of the major challenges to the industry, regional beneficiary eligibility of fish. The freshwater stingrays of gender Potamotrygon and Paratrygon come in over the past five years by participating systematically landing fishing in the Amazon region, so much so that currently fishing fleets are especially equipped to perform the capture of stingrays. However, all this effort is being applied without information on the technological characteristics of the species, which could subsidize decisions on methods and processes. Therefore, the purpose of this study was to characterize technology and the profile of fatty acids of the species Paratrygon aiereba and Potamotrygon motoro aiming to contribute to a better utilization of industrial species and subsidize the formulation of diets. The two copies of freshwater stingrays had a good income meat of pectoral fin, with 35.12% for P. aiereba and 32.35% P. motoro. Data from proximate composition were close to those established for other species of fish, featuring the two species of stingrays as leanness (<1% fat). The profile of fatty acids indicated as the majority arachidonic acid (20: 4n-6) and palmitic (16: 0). The indices of arachidonic acid obtained in the two species was respectively 29.16% in individuals of P. Motoro collected in the period of flooding in the lake of Moreno Maia and 21.17% in individuals of P. Aiereba collected in the period of drought in the Purus river. / O pescado como alimento é uma das principais fontes de proteínas de alta qualidade, com um balanceamento de aminoácidos essenciais, além da qualidade dos lipídeos, grande fonte de ácidos graxos poliinsaturados. Ao longo dos anos o pescado tem sido a principal fonte de nutrientes de origem animal na Amazônia e o aproveitamento dos recursos pesqueiros de forma racional é um dos grandes desafios à indústria de beneficiamento do pescado regional. As arraias do gênero Potamotrygon e Paratrygon vêm nos últimos 5 anos participando sistematicamente do desembarque pesqueiro na região amazônica, tanto assim que atualmente frotas pesqueiras estão equipadas especialmente para efetuar a captura de arraias. Entretanto, todo esse esforço vem sendo aplicado sem informações relativas às características tecnológicas das espécies, que poderiam subsidiar decisões em métodos e processos. Neste sentido, a proposta deste trabalho foi realizar a caracterização tecnológica e o perfil de ácidos graxos das espécies Paratrygon aiereba e Potamotrygon motoro visando contribuir para um melhor aproveitamento industrial das espéciese subsidiar a formulação de dietas. Os dois exemplares de arraia apresentaram um bom rendimento cárneo das nadadeiras peitorais, com 35,12% para P. aiereba e 32,35% P. motoro. Os dados de composição centesimal ficaram próximos aos estabelecidos para outras espécies de peixes, caracterizando as duas espécies de arraias como magras (<1% de gordura). O perfil de ácidos graxos indicou como majoritários os ácidos araquidônico (20:4n-6) e palmítico (16:0). Os índices de ácido araquidônico obtidos nas duas espécies foi respectivamente 29,16% em indivíduos de P. motoro coletados no período de enchente no lago do Moreno Maia e 21,17% em indivíduos de P. aiereba coletados no período da seca no rio Purus.