Made available in DSpace on 2016-07-18T17:53:10Z (GMT). No. of bitstreams: 1 Alini Soriano.pdf: 205994 bytes, checksum: 47ab15d5ec56c365d78a16b0973e250d (MD5) Previous issue date: 2012-09-27 / The toxocariasis is a disease of worldwide distribution, caused by nematodes Toxocara canis and T. cati, parasites whose definitive hosts are dogs and cats, respectively. These agents can also infect humans, and their larvae can migrate through the body, causing the syndrome of visceral larva migrans (visceral toxocariasis) or ocular (ocular toxocariasis). Consumption of raw or undercooked meat of animals such as ruminants and poultry has been considered as one of the routes of transmission of the disease to humans. Evaluation of the migration of larvae Toxocara spp. in fish is scarce in the literature. This study aimed to evaluate the ability of Toxocara canis to infect and migrate through the tissues of experimentally infected fish. Forty-nine Nile tilapia (Oreochromis niloticus, Linnaeus 1757) were evaluated. Two groups were formed for the assessment of infection. Group I consisted of 35 animals infected by oral gavage with 1,000 T. canis-embryonated eggs (IG). The second group contained 14 animals that received 1.0 ml PBS by oral gavage and served as a control group (CG). To recover the larvae, 5 animals from IG and two animals from CG were euthanised at 1, 2, 5, 10, 15, 30 and 60 days post-infection. Samples of the liver, brain, gills, muscle and intestinal content were collected and subjected to acid digestion and the modified Baermann method. There were no T. canis larvae detected at any time point during this experiment, but embryonated eggs were found in the intestinal contents. Our findings suggest that tilapia could serve as a disseminating vehicle of Toxocara spp. in aquatic environments. / A toxocaríase é uma doença de distribuição mundial, causada pelos nematódeos Toxocara canis e T. cati, parasitos cujos hospedeiros definitivos são os cães e os gatos, respectivamente. Esses agentes podem também infectar seres humanos, e suas larvas podem migrar pelo organismo, ocasionando a síndrome de larva migrans visceral (toxocaríase visceral) ou ocular (toxocaríase ocular). O consumo de carne crua ou mal cozida de animais, como ruminantes e aves, tem sido considerado como uma das vias de transmissão da doença para o ser humano. A avaliação da migração de larvas de Toxocara spp. em peixes é escasso na literatura. Com objetivo de criar um modelo experimental e avaliar a viabilidade da infecção e migração tecidual de Toxocara canis em peixes, foram utilizadas 49 tilápias (Oreochromis niloticus), com peso aproximado de 100 a 150 g, obtidas de uma central de piscicultura. Dois grupos foram formados para avaliação da infecção. O Grupo I (GI) composto por 35 animais infectados oralmente, por gavagem, com 1000 ovos larvados de T. canis diluídos em 1,0 mL de solução salina tamponada (PBS pH 7,0). O segundo grupo (GII) constituído por 14 animais, que receberam, pela mesma via, 1,0 mL de PBS, e serviram como controle. Os peixes foram mantidos em caixas plásticas, com fluxo de água contínuo, e alimentados com ração comercial para peixes duas vezes/dia. Nos dias 1, 2, 5, 10, 15, 30 e 60 pós-infecção, cinco animais do GI e dois do GII foram sacrificados, e amostras de fígado, sistema nervoso central, arcos branquiais, musculatura (filé) e o conteúdo intestinal foram coletados e submetidos ao processo de digestão em ácido clorídrico 0,5% e ao método de Baermann, modificado, para recuperação das larvas. Não foram encontradas larvas de T. canis em nenhum dos momentos deste experimento. No conteúdo intestinal, foram encontrados ovos larvados (5 ovos em média), em todas as tilápias infectadas. Os ovos de T. canis podem ser dispersados no ambiente aquático pela tilápia.

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Orientador: Cesar Martins / Resumo: Os cromossomos B ocorrem em cerca de 2.828 espécies de diferentes táxons, sendo basicamente heterocromáticos e compostos de DNAs repetitivos. Recentemente, análises genômicas em larga escala estão sendo utilizadas para elucidar questões acerca dos cromossomos supranumerários. Os peixes ciclídeos recebem grande interesse científico, uma vez que muitas espécies passaram por um rápido e extenso processo de radiação adaptativa. Em algumas espécies do grupo, como Astatotilapia latifasciata, foi descrita a presença de cromossomos B. Neste trabalho foi caracterizado o perfil de expressão proteico em tecidos específicos na A. latifasciata e realizada análise funcional da presença do cromossomo B nesta espécie de teleósteo, elucidando a influência que este pode acarretar em vias metabólicas específicas. Além disso, esses dados foram integrados com os resultados de RNA-Seq dessa espécie, e construídas sub redes de co-expressão e interação proteína-proteína. Também foi calculada a entropia de Shannon, a qual não apresentou diversidade na expressão dos transcritos em cada biblioteca comparada. Além disso, foi analisada a expressão diferencial de RNAm em cada tecido em relação a presença do cromossomo B e ao sexo. Dentre os transcritos diferencialmente expressos, a análise de enriquecimento funcional apresentou processos relacionados ao ciclo celular, resposta imune e resposta ao estresse. Na maioria dos casos analisados entre a expressão de proteínas, os transcritos up regulated e as sub... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The B chromosomes occur in about 2,828 species of different taxa, being heterochromatic and composed of repetitive DNA.Recently, large-scale genomic analyzes are being used to elucidate questions about supernumerary chromosomes.Cichlid fish are of great scientific interest, since many species have gone through a rapid and extensive process of adaptive radiation.In some species of the group, such as Astatotilapia latifasciata, the presence of B chromosomes was described.In this work, we characterize the profile of protein expression in specific tissues in A. latifasciata and performed a functional analysis of the presence of the B chromosome in this species of teleost, elucidating the influence that it can cause in specific metabolic pathways.In addition, we integrate these data with the RNA-Seq results of this species, and construct sub-networks of co-expression and protein-protein interaction.The Shannon entropy was also calculated, which did not show diversity in the expression of the transcripts in each library. In addition, differential expression analysis was performed on each tissue separately and the relationship between the presence of B chromosome and sex chromosome was analyzed. Among the differentially expressed transcripts, functional enrichment analysis presented processes related to the cell cycle, immune response and stress response. In relation to abundance of proteins, the up regulated transcripts and the sub-networks we identified genes like the Aurora kinas... (Complete abstract click electronic access below) / Doutor

Cichlid visual system is highly adaptive to the environment. Fish visual abilities are deter- mined by composition of opsin-based photosensitive pigments located in photoreceptor cells (rods and cones) as well as their distribution. In this thesis, four species of Lake Barombi Mbo cichlids were targeted: Stomatepia mariae, Konia eisentrauti, Konia dikume and Myaka myaka. Shallow-water cichlids K. eisentrauti and S. mariae express these types of cone opsin genes: LWS, RH2A (RH2Aβ more than RH2Aα), SWS2A and SWS2B. Contra- rily, both seasonally deep-water M. myaka and deep-water K. dikume lack expression of SWS2B and LWS in their retinae, but they express SWS2A and RH2Aα more than RH2Aβ, which corresponds to modified light conditions in deep water - a dimmer habitat lacking marginal parts of the spectrum (i.e., ultraviolet and red wavelengths). The photoreceptor distribution of selected species was investigated by means of fluorescent in situ hybridi- zation (FISH) in order to understand the performance and evolution of their visual per- ception with emphasis on the effect of depth. Distinctively, cichlid cones are arranged in a retinal mosaic consisting of short-wavelength sensitive single cones, each surrounded by four long-wavelength sensitive double cones. In this thesis, the same arrangement is...

Diplotaxodon limnothrissa Turner (1995) is a widely distributed species occurring throughout Lake Malawi, extending from the surface to a depth of at least 220m. It is probably the most abundant cichlid in the lake with biomass estimates of around 87 000 tonnes in the pelagic zone alone. The species is exploited commercially in the southern part of the lake but since its inception the fishery has never been assessed. As such this study investigates some aspects of age and growth of the species besides applying a yield-per-recruit analysis to assess the status of the fishery. Analysis of sectioned sagittal otoliths revealed that D. limnothrissa is fast growing and relatively long-lived species, attaining ages in excess of 10 years. Growth in length was rapid in immature fish, with fish attaining almost half of their maximum size within their first year. Le ngth-at-age was described by the von Bertalanffy growth model with combined-sex growth described as Lt = 211.21(1-exp(- 0.24(t+1.36))) mm TL. Total, natural and fishing mortalities were estimated at 0.76 yr⁻¹, 0.31 yr⁻¹ and 0.45 yr⁻¹ respectively. Per-recruit analysis indicated that the D. limnothrissa stock in the southeast arm of the lake is fully exploited as indicated by the current spawner biomass-per-recruit ratios of 31-55% (SB/R)F=0. Modelling indicated that the current age-at-capture (2.67 years) is lower than the age at which yield is optimised (> 5 years) based on the F₀·₁ harvesting strategy. It is, therefore, recommended that the age-at-capture should be increased from 2.67 to 5 years to optimise yield.

M.Sc. (Zoology) / A number of chemical substances in mining, industrial, agricultural and domestic effluents are likely to contaminate watercourses. These toxicants have a definite effect on all aquatic life, even at sublethal concentrations. Due to the extensive copper mining activities in the Phalaborwa region, there is concern that the sublethal effect of copper might affect the physiology of fish in the Olifants River, Kruger National Park, Transvaal. Copper can be found as an essential micronutrient in nearly all waters, although anthropogenic sources such as metals from mining and planting industries might produce environmental concentrations causing toxic effects to fish. Several effects of exposure to sublethal concentrations of copper have already been reported in fish, In the present study, the blood coagulation, general haematology, osmoregulation and differential white blood cell counts of the Mozambique tilapia, Oreochromis mossambicus were investigated after the exposures to sublethal concentrations of copper, for a short-term (96 hours) exposure as well as a long-term (four weeks) exposure in experimental flow through systems, at both 29 ± I°C and 19 ± I°C. After the respective sublethal exposures, changes in the values of blood coagulation, general haematology, osmoregulation and differential white blood cell counts were obtained, to determine the effects of the chosen copper concentrations on the blood physiology of O. mossambicus, at 29 + 10 and 19 ± I°C, respectively. After a photographic observation of blood, during all the phases of coagulation was made, it was evident that the exposure to copper, at both temperatures, resulted in delays of the blood coagulation times as well as decreases in the elasticity of the clots that formed. Copper was found to induce haemophilia at 29 ± I°C and 19 ± l°C. whilst at 19 ± I°C it also induced thrombocytopenia. Thus exposure to copper lead to coagulation defects which caused haemorrhage which can eventually cause the death of these fish...

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.

Summary: The thesis comprises from the introduction and five main parts: three of them are published papers, the rest two are manuscripts prepared for submitting to the scientific journals. The first two are published phylogenetic studies of the cichlasomatine cichlids based on (1) molecular characters, and (2) both morphological and molecular data with the description of a new genus Andinoacara. The third (3) is the already published description of the new species Andinoacara stalsbergi from Peru combining both morphological and phylogenetic approaches and including the detailed phylogeny of the genus Andinoacara. The next unpublished manuscript (4) is the more detailed comprehensive phylogeography of the two non-relative genera (including Andinoacaras) of the trans-Andean cichlids. Including all valid species from the majority of their distribution areas it was reconstructed the ancestral area of both genera in the Choco region, Colombia, and revealed the directions of their distribution spreading. The last (5) unpublished manuscript is the phylogeographical study of the cichlid genus Serranochromis from the headwaters of the totally unknown Central Angola. It showed several evidences of the faunal exchange among the adjacent river systems. Lastly, the thesis is supplemented by several appendices...

In order to ascertain the degree of compatibility in developmental restructuring and behavioral plasticity between two fish species frequently made subject of laboratory research (Metriaclima zebra & Danio rerio), alternative trophic niche exposure experiments utilizing novel three-prong feeding treatments were conducted to obtain morphometric data, which demonstrated both species do bear some degree of plasticity. The results are somewhat complicated by differences in locality of detectable restructuring, which may be due to disparity in the form-function relationship for each species’ lineage. Each is notable in the manner of respective species’ jaw protrusion, as it is driven by anterior kinethmoid rotation in D. rerio. as opposed to force imparted upon the rostral cartilage of the premaxilla’s articular process in M zebra. Each is markedly distinct in the pharyngeal jaw as well, as zebrafish (also toothless at the oral jaw) bear teeth only on the lower set at the posterior of the mouth, while cichlids bear teeth on all jaws and additionally possess a unique, fused lower pharyngeal jaw. However, accounting for this difference in experimental models does allow for direct comparison, both at the morphological/behavioral and potentially the genetic level, though additional research is necessary. The evidence provided here also provides encouragement that more nuanced approaches to laboratory trophic niche exposure experiments could elucidate further evidence on the nature of phenotypic plasticity.

The evolution of jaws in cichlid fishes of the East African Great Lakes is a textbook example of adaptive radiation in vertebrates. Karl Liem postulated that this adaptive radiation has been possible due to the functional decoupling of two cichlid functional units – the pharyngeal jaw (PJ) and the oral jaw (OJ). This functional decoupling of the jaws has enabled the OJ to be relieved of its dual role of prey capturing and processing and has allowed the PJ to take on the role of prey processing. As a result, African cichlids have adapted the morphology of their functional units (i.e., oral jaws) to specialize in a feeding mechanism best suited for their habitat. However, global morphological changes (across the OJ and PJ) are understudied, especially, at the genetic level. In this study, two rock dwelling species of African Cichlids from Lake Malawi were used - Labeotropheus fuelleborni (LF) and Tropheops “red cheek” (TRC). Both species have distinct craniofacial morphologies for specialized benthic feeding (LF) and for generalized feeding (TRC). This morphological variation allowed us to investigate the functional decoupling of the jaws by studying differences in bone shape and muscle volumes in an F5 hybrid population. Strong phenotypic correlations were observed between and within the tissues of the OJ and PJ. Further, to identify phenotype to genotype associations, a Quantitative Locus (QTL) analysis and a fine mapping analysis was conducted. The results show some evidence of overlapping genetic control (i.e., pleiotropy) suggesting some genetic coupling between the two jaws.