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1

Agmon, Eran. "A Computational Model of Adaptive Sensory Processing in the Electroreception of Mormyrid Electric Fish." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/291.

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Electroreception is a sensory modality found in some fish, which enables them to sense the environment through the detection of electric fields. Biological experimentation on this ability has built an intricate framework that has identified many of the components involved in electroreception's production, but lack the framework for bringing the details back together into a system-level model of how they operate together. This thesis builds and tests a computational model of the Electrosensory Lateral Line Lobe (ELL) in mormyrid electric fish in an attempt to bring some of electroreception's structural details together to help explain its function. The ELL is a brain region that functions as a primary processing area of electroreception. It acts as an adaptive filter that learns to predict reoccurring stimuli and removes them from its sensory stream, passing only novel inputs to other brain regions for further processing. By creating a model of the ELL, the relevant components which underlie the ELL's functional, electrophysiological patterns can be identified and scientific hypotheses regarding their behavior can be tested. Systems science's approach is adopted to identify the ELL's relevant components and bring them together into a unified conceptual framework. The methodological framework of computational neuroscience is used to create a computational model of this structure of relevant components and to simulate their interactions. Individual activation tendencies of the different included cell types are modeled with dynamical systems equations and are interconnected according to the connectivity of the real ELL. Several of the ELL's input patterns are modeled and incorporated in the model. The computational approach claims that if all of the relevant components of a system are captured and interconnected accurately in a computer program, then when provided with accurate representations of the inputs a simulation should produce functional patterns similar to those of the real system. These simulated patterns generated by the ELL model are compared to recordings from real mormyrid ELLs and their correspondences validate or nullify the model's integrity. By building a computation model that can capture the relevant components of the ELL's structure and through simulation reproduces its function, a systems-level understanding begins to emerge and leads to a description of how the ELL's structure, along with relevant inputs, generate its function. The model can be manipulated more easily than a biological ELL, and allows us to test hypotheses regarding how changes in the structures affect the function, and how different inputs propagate through the structure in a way that produces complex functional patterns.
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2

Worm, Martin [Verfasser]. "Animal-Robot Interactions: Electrocommunication, Sensory Ecology, and Group Dynamics in a Mormyrid Weakly Electric Fish / Martin Worm." Bonn : Universitäts- und Landesbibliothek Bonn, 2018. http://d-nb.info/1173789774/34.

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3

LITEL, CATHERINE. "Rythmes de decharge de poissons electriques (mormyridae) : aspects structuraux et fonctionnels." Tours, 1997. http://www.theses.fr/1997TOUR4020.

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Les mormyres, poissons des eaux douces africaines, emettent en permanence des impulsions de quelques volts ayant un role d'electrolocalisation et d'electrocommunication. Ces impulsions, de forme et d'intensite constantes pour un individu donne, sont emises a des intervalles de temps (intervalles inter-impulsions) tres variables. Deux parametres ont ete utilises pour caracteriser ces rythmes de decharge : le nombre d'impulsions par seconde (cadence de decharge) et leur organisation temporelle. La nature, les causes, et les fonctions de la variabilite de ces rythmes font l'objet de notre etude. Une description des rythmes emis par des individus isoles, sous l'influence de divers facteurs (cycle circadien, presence de nourriture, comportement locomoteur, espece et stade de developpement), montre que la cadence et l'organisation temporelle portent des indications sur l'activite locomotrice, les especes et les individus. Ces deux parametres pourraient donc avoir un role de communication. Place dans une situation de choix entre un individu familier et un individu inconnu g. Petersii montre une attirance pour l'individu familier. Cette attirance est cependant trop faible pour tenter d'isoler les signaux impliques. Une experience de conditionnement montre que g. Petersii discrimine des rythmes synthetiques de decharge qui different a la fois par leur cadence et leur organisation temporelle ou uniquement par leur cadence. Aucune discrimination n'est observee entre des rythmes ne differant que par leur organisation temporelle. Une experience de double choix, utilisant les reponses spontanees des poissons a des stimuli naturels et synthetiques, confirme la predominance de la cadence de decharge. La cadence etant contrainte par la fonction d'electrolocalisation, peut-on parler de communication chez les poissons electriques ou s'agit-il d'une forme particuliere d'eavesdropping ou un signal emis par un individu pour une fonction d'electrolocalisation est utilise par un congenere ?
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4

Graff, Christian. "Signaux électriques et comportement social du poisson à faibles décharges, Marcusenius macrolepidotus (mormyridae, teleostei)." Paris 11, 1986. http://www.theses.fr/1986PA112054.

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Cette thèse concerne Marcusenius macrolepidotus (mormyridae, teleostei), poisson émetteur de faibles impulsions électriques. Elle décrit son comportement social locomoteur et électrique. Les organes émetteurs et récepteurs d'électricité sont révélés histologiquement. Les mouvements de groupes sont observés en milieux variés puis quantifiés en conditions expérimentales permettant simultanément l'enregistrement de l'activité électrique du groupe et celle d'un individu dans le groupe. Les activités électriques sont analysées à l'ordinateur. L'activité électrique présente des stéréotypies propres à chaque individu, elle change avec l'activité locomotrice. Cette espèce présente une tendance variable au regroupement des individus. L'activité électrique globale du groupe diffère d'un mélange d'activités électriques individuelles par des réponses d'arrêts en groupe et des réponses-écho entre individus. Ce travail met en évidence un système social construit sur des signaux de communication auxquels l’homme est insensible<br>This thesis deals with Marcusenius rnacrolepidotus (mormyridae), a teleost fish, emitter of weak-electric pulses. Its locomotor and electric social behaviours are described. The histology of the electric emitter- and receptor organs is presented. The movements of groups are first observed in various environments, and then quantified in experimental conditions. A novel set-up simultaneously records the electric pulses from the group and from one (individual) fish within the group. A computer analyses the rythm of interpulse intervals. The electric activity of each fish shows individual stereotypies. It changes according to locomotor activity. Fish of this species show a tendancy to aggregate depending on the situation. The group's electric activity differs from a random mix of individual electric activities because of two types of interactions, namely stopping responses (to one fish, from the rest of the group), and echo responses (between two fish in the group). These results show a social system built on communication signals to which humans are insensible
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5

Besseau, Laurence. "L'hermaphrodisme protandre chez les sparidés : les potentialités de l'ovotestis dans le modèle Lithognathus mormyrus." Perpignan, 1991. http://www.theses.fr/1991PERP0114.

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L'etude de la sexualite du marbre, lithognathus mormyrus, est apprehendee par une analyse biometrique, sclerochronologique, histologique et cytologique d'une population du littoral mediterraneen roussillonnais. Les parametres de la croissance du marbre sont estimes par ajustement au modele de von bertalanffy. Trois types d'architecture de la sagitta (meb) sont mis en relation avec le statut sexuel des poissons. Les modalites de la gonadogenese chez l. Mormyrus sont decrites: a deux mois, la bisexualite est acquise. Chez des specimens d'un an, trois types d'ovotestis juveniles sont identifies: prevalence testiculaire, equivalence testiculaire et ovarienne, prevalence ovarienne. Les cycles saisonniers de reproduction sont caracterises: repos sexuel d'octobre a mars, gametogenese d'avril a juillet, ponte en aout-septembre et post ponte en septembre. La structure sexuelle de la population est apprehendee par l'analyse de la distribution de frequence de taille, en relation avec le sexe (observations macro- & microscopiques). La moitie seulement de la population est hermaphrodite protandre. 50% des poissons sont gonochoriques secondaires: 40% de femelles primaires et 10% de males persistants. La protandrie n'est donc pas exclusive chez l. Mormyrus. L'inversion sexuelle protandre se realise en 2 etapes (met): 1) l'achevement de l'edification de l'aire ovarienne, durant la phase male fonctionnelle, est un phenomene discontinu, cyclique (en periode post ponte) et discret. 2) la regression du territoire testiculaire, pendant la phase femelle fonctionnelle, est un phenomene continu, qui procede de la degenerescence des spermatogonies, phagocytees par les cellules de sertoli. Des cellules immunitaires interviennent secondairement dans la resorption du materiel male degenerescent, conduisant a la formation de corps bruns (lipofuscines). Les potentialites de l'ovotestis de sparides dans l'expression du sexe sont estimees et discutees
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6

Graff, Christian. "Signaux électriques et comportement social du poisson à faibles décharges, Marcusenius macrolepidotus, Mormyridae, teleostei." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37598011n.

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7

Feulner, Philine. "Adaptive radiation, speciation, and reproductive isolation in African weakly electric fish : (Genus Campylomormyrus, Mormyridae, Teleostei)." Phd thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981698271.

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8

DJEBAR, A. BORHANE. "Contribution a l'etude du metabolisme du glycogene dans les cellules sensorielles d'un electrorecepteur des mormyrides (teleosteens)." Paris 6, 1986. http://www.theses.fr/1986PA066551.

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Le glycogene represente dans les cellules sensorielles des electrorecepteurs cutanes d'un normyride gnathonemus petersii, une source energetique de reserve destinee a soutenir l'autoactivite electrique de ces cellules pourvues de connexions anatomo-fonctionnelles intactes
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9

Djebar, Abdellah-Borhane. "Contribution à l'étude du métabolisme du glycogène dans les cellules sensorielles d'un électrorécepteur des mormyrides, téléosteens." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375972020.

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10

Gebhardt, Kristina [Verfasser]. "Kommunikation mittels selbst generierter elektrischer Signale innerhalb sozialer Gruppen des schwach elektrischen Fisches Mormyrus rume / Kristina Gebhardt." Bonn : Universitäts- und Landesbibliothek Bonn, 2012. http://d-nb.info/1044846828/34.

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11

Al-Azemi, B. M. "Ultrastructural and morphometric studies on the gills of the freshwater fish Gnathonemus Petersii (family : Mormyridae) exposed to selected pollutants." Thesis, Royal Holloway, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525080.

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The histopathological effects of three heavy metals, cyanide and atrazine on the gill tissues of the mormyrid fish, Gnathonemus petersii, were determined primarily by electron microscopy. Replicate samples of fish were exposed for 6 hours to acute and subacute concentrations of each toxicant in a continuous flow system comprising aerated, dechlorinated and heated water. Specific alterations to gill ultrastructure were found to be associated with each toxicant. Cadmium damage at 1.0 mg 1.1 was associated with the formation of large subepithelial spaces within the secondary lamellae and at 10.0 mg 1,1 with lamellar aneurism. Chromium caused epithelial hyperplasia at 1.0 mg 1'1 and extensive fusion of secondary lamellae at 10.0 mg 1'1. Copper exposure stimulated hyperactivity of mucous cells at 0.1 mg 1'1 which resulted in the accumulation of a thick layer of mucus on the gills at 0.5 mg 1,1. Cyanide caused desquamation of filamental epithelium at 0.05 mg 1'1 and stripping of the epithelium and underlying tissue down to the supporting cartilage at 0.1 mg 1'1. Atrazine damage was characterized by the presence of breaks in the gill epithelium at 0.5 mg 1,1 which developed into deep pits at 5.0 mg 1'1. Morphometric measurements of the structural components of secondary lamellae revealed quantitative differences in tissue alterations among fish exposed to different toxicants. A significant increase in the volume of secondary lamellae has been found in fish exposed to heavy metals. On the other hand, fish exposed to atrazine and 0.1 mg 1,1 cyanide showed a sharp decrease in lamellar volume. The increase in lamellar volume in fish exposed to heavy metals was also accompanied by a reduction in the interlamellar water spaces and a significant increase in the water-blood diffusion distance. In cadmium-exposed fish the increase in lamellar volume was mainly attributed to the increase in the subepithelial spaces at 1.0 mg 1'1 or in the volume of blood components due to aneurism at 10.0 mg 1'1. In'fish exposed to chromium it was attributed to the thickening of the epithelial layer as a result of epithelial hyperplasia; or epithelial hypertrophy in copper-exposed fish. On the other hand, the decrease in lamellar volume in fish exposed to 0.10 mg 1'1 cyanide was mainly attributed to the decrease in the volume of the tissue-occupied region outside the basement membrane due to the stripping of lamellar epithelium. In both concentrations ofatrazine (O.S and S.O mg 1'1) the different components of the secondary lamella contributed to the decrease in lamellar volume. These morphometric analyses confirm observations made by electron microscopy. The present study, therefore, demonstrates the potential of electron microscopy, in particular SEM, as a tool for detecting pollutant-induced damage to the surface of fish gills. Preliminary work with chromium has indicated that comparative ultrastructural studies are now needed to further our understanding of the chronic exposure of fish to these toxic chemicals.
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12

Kaifosh, Patrick William John. "The neural circuit basis of learning." Thesis, 2016. https://doi.org/10.7916/D8416WXR.

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The astounding capacity for learning ranks among the nervous system’s most impressive features. This thesis comprises studies employing varied approaches to improve understanding, at the level of neural circuits, of the brain’s capacity for learning. The first part of the thesis contains investigations of hippocampal circuitry – both theoretical work and experimental work in the mouse Mus musculus – as a model system for declarative memory. To begin, Chapter 2 presents a theory of hippocampal memory storage and retrieval that reflects nonlinear dendritic processing within hippocampal pyramidal neurons. As a prelude to the experimental work that comprises the remainder of this part, Chapter 3 describes an open source software platform that we have developed for analysis of data acquired with in vivo Ca2+ imaging, the main experimental technique used throughout the remainder of this part of the thesis. As a first application of this technique, Chapter 4 characterizes the content of signaling at synapses between GABAergic neurons of the medial septum and interneurons in stratum oriens of hippocampal area CA1. Chapter 5 then combines these techniques with optogenetic, pharmacogenetic, and pharmacological manipulations to uncover inhibitory circuit mechanisms underlying fear learning. The second part of this thesis focuses on the cerebellum-like electrosensory lobe in the weakly electric mormyrid fish Gnathonemus petersii, as a model system for non-declarative memory. In Chapter 6, we study how short-duration EOD motor commands are recoded into a complex temporal basis in the granule cell layer, which can be used to cancel Purkinje-like cell firing to the longer duration and temporally varying EOD-driven sensory responses. In Chapter 7, we consider not only the temporal aspects of the granule cell code, but also the encoding of body position provided from proprioceptive and efference copy sources. Together these studies clarify how the cerebellum-like circuitry of the electrosensory lobe combines information of different forms and then uses this combined information to predict the complex dependence of sensory responses on body position and timing relative to electric organ discharge.
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13

Muller, Salomon. "Learning in Multi-Layer Networks of the Brain." Thesis, 2021. https://doi.org/10.7916/d8-wh1n-c795.

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Simple circuits perform simple tasks. Complex circuits can perform more complicated tasks. This is true for artificial circuits and for brain circuits. As is known from artificial networks, a complexity that makes circuits substantially more powerful is distributing learning across multiple layers. In fact, most brain circuits in vertebrate systems are multi-layer circuits (but for few that perform simple reflexes) in which learning is distributed across layers. Despite the crucial contribution of learning in middle layer neurons to the output of the circuits they are embedded in, there is little understanding of the principles defining this contribution. A very common feature in brain circuits is that middle layer neurons generate two types of signals, known as spikes. These middle layer neurons commonly have long dendrites where they generate dendritic spikes. As well, like most neurons, they generate axonal spikes near the cell body. Neurons exhibiting these two spike types include pyramidal cells in the neo-cortex and the hippocampus, the Purkinje cells in the cerebellum and many more. In this thesis I study another circuit that contains middle layer neurons, the electrosensory lateral lobe (ELL) of the mormyrid fish. The ELL is a tractable brain circuit in which the middle layer neurons generate dendritic and axonal spikes. In this thesis I show that these spike types are not two different expressions of the same inputs. Rather, they have a symbiotic relationship. Instead of all inputs triggering both spikes, some inputs can selectively drive dendritic spikes. The dendritic spikes in return modify the synaptic strength of another set of inputs. The modified inputs are then transmitted to downstream neurons via the axonal spikes, which contributes a desired signal to the output of the circuits. Effectively there is a separation of learning and signaling in the middle layer neurons through the two spike types. Having two types of spikes in the same neuron doing different computations enormously expands the computational power of the neuron. But, being in the same neuron means the separation of function is constrained and needs to be supported by biophysical principles. I have thus built a biophysical model to understand the biophysical principles underlying the separation of function. I show that in the middle layer neurons of the ELL, the axonal spikes are strongly reduced in amplitude as they backpropagate to the apical dendrites, yet they remain crucial in driving dendritic spikes. Critically, modulation of inhibitory inputs can selectively dial up or down the ability of the backpropagating axonal spikes to drive dendritic spikes. Thus, a set of inhibitory modulating inputs can selectively modulate dendritic spikes. Having learning in different layers contributing to the outcome of the circuit, naturally leads to asking how the work is divided across layers and neuron types within the circuit. In this thesis I answer this question in the context of the outcome of the ELL circuit. Finally, another signature of a complex circuit is the ability to integrate many different inputs, usually in middle layer neurons, to generate sophisticated outputs. A goal for scientists studying systems neuroscience is to understand how this integration works. In this thesis I provide a coherent model of a learning behavior called vestibulo occular reflex (VOR) adaptation, that depends on the integration of separate inputs to yield a learned behavior. The VOR is a simple reflex generated in the brain stem. Inputs from the brain stem are also sent to an area in the cerebellar cortex called the flocculus. The flocculus also receives another set of inputs that generate a different behavior, called smooth-pursuit. The integration of VOR inputs with smooth-pursuit inputs in the flocculus generate VOR adaptation. Understanding complex circuits is one of the greatest challenges for today's neuroscientists. In this thesis I tackle two such circuits and hope that through a better understandings of these circuits we gain principles that apply to other circuits and thereby advance our understanding of the brain.
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14

Feulner, Philine [Verfasser]. "Adaptive radiation, speciation, and reproductive isolation in African weakly electric fish: (Genus Campylomormyrus, Mormyridae, Teleostei) / von Philine Feulner." 2006. http://d-nb.info/981698271/34.

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15

Machnik, Peter [Verfasser]. "Allopatrische Differenzierung der Elektrokommunikation der Bulldog-Fische des südlichen Afrika (Marcusenius-macrolepidotus-Komplex, Mormyridae, Teleostei) / vorgelegt von Peter Machnik." 2009. http://d-nb.info/1005058830/34.

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16

Reis, Catarina Isabel Nogueira de Carvalho dos. "Estudo comparativo da ecologia alimentar de Pagrus pagrus L. (1758), Lithognatus mormyrus L. (1758) e Ciplodus sargus L. (1758) (Pisces, Sparidae) da costa algarvia." Master's thesis, 1998. http://hdl.handle.net/10400.1/8604.

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Dissertação de mest. em Estudos Marinhos e costeiros, Unidade de Ciências e Tecnologias dos Recursos Aquáticos, Univ. do Algarve, 1998<br>No presente estudo descreve-se a ecologia alimentar de três espécies de Sparídeos da costa Algarvia, cuja importância económica é elevada e que se encontram comercialmente ameaçadas, analisando e comparando os seus hábitos alimentares através de métodos quantitativos (coeficiente de vacuidade e índice de replecção) e métodos qualitativos (percentagem em número, frequência de ocorrência e percentagem em peso). As presas preferenciais foram determinadas pelo coeficiente alimentar de HUREAU (Q) e pelo índice de importância relativa (I.R.I.). Foi analisado um total de 105 indivíduos (46 de Pagrus pagrus, 37 de Lithognathus mormyrus e 22 de Diplodus sargus) capturados por redes de emalhar entre Abril de 1995 e Maio de 1997. As espécies P. pagrus e L. mormyrus evidenciaram um carácter generalista no seu padrão de alimentação, ingerindo um elevado número de taxa distintos, enquanto que a espécie D. sargus apresentou uma dieta mais restrita, composta maioritariamente de moluscos bivalves. O estudo da sobreposição dos regimes alimentares destas três espécies revelou a existência de um grau de sobreposição significativo. As espécies em estudo podem ser consideradas como consumidores secundários, que se alimentam de organismos planctonívoros e herbívoros, podendo ser incluídas, por isso, no nível trófico 3 de LINDEMAN.<br>This study presents data on the diet of three Sparid species from the South coast of Portugal (Algarve), that are commercially important, but also in danger of over-exploitation. Data were analyzed with numeric methods (fullness Index) and qualitative methods (percentage of occurrence and weight and number percentage). The index of relative importance (I.R.I.) and the HUREAU s feeding coefficient (Q) were used to determine prey importance. A total of 105 fish (46 Pagrus pagrus, 37 Lithognathus mormyrus and 22 Diplodus sargus) were obtained from local gillnet fishery between April 1995 and May 1997. P. pagrus and L mormyrus were relatively euryphagous, preying upon a high number of taxa, while D. sargus had a more specialized diet, composed mainly of mollusc bivalves. Overlap analysis revealed that there was a significant overiap between the diet of this three species. Ali species were considered as secondary predators and therefor included in LINDEMAN's trophic levei 3.<br>Programa PRAXIS XXI(BM /7082/95)
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