No description available.

Desenvolvemos um método capaz de reconhecer assinaturas de descargas do órgão elétrico de peixes de campo elétrico fraco da espécie Gymnotus carapo. A assinatura de um peixe é computada com base no espectro de frequências de suas descargas, extraído por meio de uma transformada de Fourier, ou com base em uma análise tempo-frequência das mesmas, realizada por meio de uma transformada complexa de dupla árvore de pacote wavelet. Com o auxílio de uma máquina de vetores de suporte, um método de classificação supervisionada, utilizamos essas assinaturas para identificar, com boa precisão (estimada em 96%), o peixe de origem de cada descarga de órgão elétrico recebida durante uma aquisição com dois peixes movimentando-se livremente em um mesmo aquário. / We developed a method capable of recognizing signatures of the electric organ discharges of the weakly electric fish Gymnotus carapo. The signature of a fish is computed based on the frequency spectrum of its discharges, extracted using a Fourier transform, or based on a time-frequency analysis, done using a dual-tree complex wavelet packet transform. With the aid of a support vector machine, a supervisioned classification method, we use these signatures to identify, with good precision (estimated at 96%), the source fish of each electric organ discharge received during an acquisition with two fish freely swimming in the same aquarium.

Weakly electric fish produce and detect electric fields and use their electrosensory modality in a number of behaviours including navigation and communication. They can modulate their electric discharge in frequency and amplitude to produce electrocommunication signals in variable patterns during social interactions. In one model neuroethological species, Apteronotus leptorhynchus, the most commonly produced communication signal is the ‘small chirp’ – a brief 10-30ms modulation. Individuals tend to produce these signals at high rates during agonistic interactions. In this thesis I will explore the social value of chirps, and to a lesser extent other communication behaviours, in A. leptorhynchus using a variety of experimental designs involving different staged social contexts. I use time series analysis methods to explore the patterns of chirps produced and accompanying aggressive behaviours. I first characterize electrocommunication and chirping in pairs of free swimming fish and correlate signal production with aggressive displays. Bursts of echoed, or reciprocated, chirps tend to be produced in the intervals separating aggressive attacks. Behavioural analysis shows that fish respond to conspecific chirps with echoed chirps and decreased aggression in social contexts outside the range in which previous modelling and electrophysiological data predicted that chirps could be encoded effectively. I then characterize the chirping and aggressive responses to playbacks simulating intruders with different chirping styles to test whether alternative chirp patterns differentially influence conspecific behaviour. In response to simulated intruders producing chirps that echo the real fish’s chirps with a short latency, less aggressive fish tend to produce more of their chirps in bursts than more aggressive fish. For randomly chirping intruders, the response of fish depends on the rate of chirps delivered. Fish respond less aggressively, with fewer chirps, and echo the stimulus chirps at a higher rate when high rates of random chirps are delivered than when responding to simulated intruders with low rates of randomly delivered chirps. Further, across all playback scenarios, fish that produce chirps in response to the playbacks are more aggressive than those that do not chirp. Finally, to better understand the electrosensory inputs during these interactions, I characterize changes in the electric image received by a restrained fish during movements of a free-swimming conspecific and correlate these with chirp production. When one fish is restrained, bursts of chirps tend to be associated with approach behaviours. Communication signals often function to promote individual assessment of potential rivals during agonistic encounters and bursty, antiphonal chirp exchanges may facilitate these assessments and deter potentially costly physical escalations.

Weakly electric fish produce and detect electric fields and use their electrosensory modality in a number of behaviours including navigation and communication. They can modulate their electric discharge in frequency and amplitude to produce electrocommunication signals in variable patterns during social interactions. In one model neuroethological species, Apteronotus leptorhynchus, the most commonly produced communication signal is the ‘small chirp’ – a brief 10-30ms modulation. Individuals tend to produce these signals at high rates during agonistic interactions. In this thesis I will explore the social value of chirps, and to a lesser extent other communication behaviours, in A. leptorhynchus using a variety of experimental designs involving different staged social contexts. I use time series analysis methods to explore the patterns of chirps produced and accompanying aggressive behaviours. I first characterize electrocommunication and chirping in pairs of free swimming fish and correlate signal production with aggressive displays. Bursts of echoed, or reciprocated, chirps tend to be produced in the intervals separating aggressive attacks. Behavioural analysis shows that fish respond to conspecific chirps with echoed chirps and decreased aggression in social contexts outside the range in which previous modelling and electrophysiological data predicted that chirps could be encoded effectively. I then characterize the chirping and aggressive responses to playbacks simulating intruders with different chirping styles to test whether alternative chirp patterns differentially influence conspecific behaviour. In response to simulated intruders producing chirps that echo the real fish’s chirps with a short latency, less aggressive fish tend to produce more of their chirps in bursts than more aggressive fish. For randomly chirping intruders, the response of fish depends on the rate of chirps delivered. Fish respond less aggressively, with fewer chirps, and echo the stimulus chirps at a higher rate when high rates of random chirps are delivered than when responding to simulated intruders with low rates of randomly delivered chirps. Further, across all playback scenarios, fish that produce chirps in response to the playbacks are more aggressive than those that do not chirp. Finally, to better understand the electrosensory inputs during these interactions, I characterize changes in the electric image received by a restrained fish during movements of a free-swimming conspecific and correlate these with chirp production. When one fish is restrained, bursts of chirps tend to be associated with approach behaviours. Communication signals often function to promote individual assessment of potential rivals during agonistic encounters and bursty, antiphonal chirp exchanges may facilitate these assessments and deter potentially costly physical escalations.

Behavioural syndromes, defined as suites of correlated behaviours across different contexts, are used to characterize individual variability in behaviours. Males of the weakly electric fish species, Apteronotus leptorhynchus, produce electro-communication signals called chirps. Chirps are thought to be involved in agonistic signalling, as their relative incidence increases during agonistic conspecific interactions. However, high levels of individual variability in aggression obscure the role of chirps in mediating aggression. Here, I tested the presence of an aggression-boldness behavioural syndrome, and then considered the implications such a syndrome would have on chirping behaviours. Behavioural tests in anti-predation, object novelty, feeding, conspecific intrusion and novel environment exploration contexts revealed a syndrome involving only object novelty and feeding. We found no correlation between chirping behaviour and the assessed behaviours. Our results demonstrate that chirps represent a more complex communication system than previously suggested.

Weakly electric fish produce and detect electric fields and use their electrosensory modality in a number of behaviours including navigation and communication. They can modulate their electric discharge in frequency and amplitude to produce electrocommunication signals in variable patterns during social interactions. In one model neuroethological species, Apteronotus leptorhynchus, the most commonly produced communication signal is the ‘small chirp’ – a brief 10-30ms modulation. Individuals tend to produce these signals at high rates during agonistic interactions. In this thesis I will explore the social value of chirps, and to a lesser extent other communication behaviours, in A. leptorhynchus using a variety of experimental designs involving different staged social contexts. I use time series analysis methods to explore the patterns of chirps produced and accompanying aggressive behaviours. I first characterize electrocommunication and chirping in pairs of free swimming fish and correlate signal production with aggressive displays. Bursts of echoed, or reciprocated, chirps tend to be produced in the intervals separating aggressive attacks. Behavioural analysis shows that fish respond to conspecific chirps with echoed chirps and decreased aggression in social contexts outside the range in which previous modelling and electrophysiological data predicted that chirps could be encoded effectively. I then characterize the chirping and aggressive responses to playbacks simulating intruders with different chirping styles to test whether alternative chirp patterns differentially influence conspecific behaviour. In response to simulated intruders producing chirps that echo the real fish’s chirps with a short latency, less aggressive fish tend to produce more of their chirps in bursts than more aggressive fish. For randomly chirping intruders, the response of fish depends on the rate of chirps delivered. Fish respond less aggressively, with fewer chirps, and echo the stimulus chirps at a higher rate when high rates of random chirps are delivered than when responding to simulated intruders with low rates of randomly delivered chirps. Further, across all playback scenarios, fish that produce chirps in response to the playbacks are more aggressive than those that do not chirp. Finally, to better understand the electrosensory inputs during these interactions, I characterize changes in the electric image received by a restrained fish during movements of a free-swimming conspecific and correlate these with chirp production. When one fish is restrained, bursts of chirps tend to be associated with approach behaviours. Communication signals often function to promote individual assessment of potential rivals during agonistic encounters and bursty, antiphonal chirp exchanges may facilitate these assessments and deter potentially costly physical escalations.

Desenvolvemos um método capaz de reconhecer assinaturas de descargas do órgão elétrico de peixes de campo elétrico fraco da espécie Gymnotus carapo. A assinatura de um peixe é computada com base no espectro de frequências de suas descargas, extraído por meio de uma transformada de Fourier, ou com base em uma análise tempo-frequência das mesmas, realizada por meio de uma transformada complexa de dupla árvore de pacote wavelet. Com o auxílio de uma máquina de vetores de suporte, um método de classificação supervisionada, utilizamos essas assinaturas para identificar, com boa precisão (estimada em 96%), o peixe de origem de cada descarga de órgão elétrico recebida durante uma aquisição com dois peixes movimentando-se livremente em um mesmo aquário. / We developed a method capable of recognizing signatures of the electric organ discharges of the weakly electric fish Gymnotus carapo. The signature of a fish is computed based on the frequency spectrum of its discharges, extracted using a Fourier transform, or based on a time-frequency analysis, done using a dual-tree complex wavelet packet transform. With the aid of a support vector machine, a supervisioned classification method, we use these signatures to identify, with good precision (estimated at 96%), the source fish of each electric organ discharge received during an acquisition with two fish freely swimming in the same aquarium.

Weakly electric fish produce and detect electric fields and use their electrosensory modality in a number of behaviours including navigation and communication. They can modulate their electric discharge in frequency and amplitude to produce electrocommunication signals in variable patterns during social interactions. In one model neuroethological species, Apteronotus leptorhynchus, the most commonly produced communication signal is the ‘small chirp’ – a brief 10-30ms modulation. Individuals tend to produce these signals at high rates during agonistic interactions. In this thesis I will explore the social value of chirps, and to a lesser extent other communication behaviours, in A. leptorhynchus using a variety of experimental designs involving different staged social contexts. I use time series analysis methods to explore the patterns of chirps produced and accompanying aggressive behaviours. I first characterize electrocommunication and chirping in pairs of free swimming fish and correlate signal production with aggressive displays. Bursts of echoed, or reciprocated, chirps tend to be produced in the intervals separating aggressive attacks. Behavioural analysis shows that fish respond to conspecific chirps with echoed chirps and decreased aggression in social contexts outside the range in which previous modelling and electrophysiological data predicted that chirps could be encoded effectively. I then characterize the chirping and aggressive responses to playbacks simulating intruders with different chirping styles to test whether alternative chirp patterns differentially influence conspecific behaviour. In response to simulated intruders producing chirps that echo the real fish’s chirps with a short latency, less aggressive fish tend to produce more of their chirps in bursts than more aggressive fish. For randomly chirping intruders, the response of fish depends on the rate of chirps delivered. Fish respond less aggressively, with fewer chirps, and echo the stimulus chirps at a higher rate when high rates of random chirps are delivered than when responding to simulated intruders with low rates of randomly delivered chirps. Further, across all playback scenarios, fish that produce chirps in response to the playbacks are more aggressive than those that do not chirp. Finally, to better understand the electrosensory inputs during these interactions, I characterize changes in the electric image received by a restrained fish during movements of a free-swimming conspecific and correlate these with chirp production. When one fish is restrained, bursts of chirps tend to be associated with approach behaviours. Communication signals often function to promote individual assessment of potential rivals during agonistic encounters and bursty, antiphonal chirp exchanges may facilitate these assessments and deter potentially costly physical escalations.

Behavioural syndromes, defined as suites of correlated behaviours across different contexts, are used to characterize individual variability in behaviours. Males of the weakly electric fish species, Apteronotus leptorhynchus, produce electro-communication signals called chirps. Chirps are thought to be involved in agonistic signalling, as their relative incidence increases during agonistic conspecific interactions. However, high levels of individual variability in aggression obscure the role of chirps in mediating aggression. Here, I tested the presence of an aggression-boldness behavioural syndrome, and then considered the implications such a syndrome would have on chirping behaviours. Behavioural tests in anti-predation, object novelty, feeding, conspecific intrusion and novel environment exploration contexts revealed a syndrome involving only object novelty and feeding. We found no correlation between chirping behaviour and the assessed behaviours. Our results demonstrate that chirps represent a more complex communication system than previously suggested.

Construímos um aparato experimental para medir os instantes de disparo do órgão elétrico de peixes elétricos de campo fraco da espécie Gymnotus carapo, que produz estes pulsos para localizar objetos dentro da água e para se comunicar socialmente. O aparato foi desenvolvido de maneira a iisolar o animal de perturbações externas como vibrações mecânicas, sons, campos elétricos e variações de luminosidade do ambiente. A principal característica de nosso aparato é um conjunto de eletrodos, distribuídos nos vértices do tanque de experimentos, que permitem obter as medidas (longas séries de instantes de disparo) sem restringir os movimentos do peixe e até mesmo inferir a sua posição comparando as amplitudes em diferentes eletrodos, o que possibilita relacionar a posteriori os padrões de disparo ao comportamento do animal. Desenvolvemos um programa de computador em linguagem C que, através de uma interface digital­analógica reproduz a série temporal da voltagem de um pulso de um peixe verdadeiro e utilizamos este sinal elétrico para estimular os animais. Os pulsos artificiais foram aplicados a um dipolo elétrico que imita a geometria do órgão elétrico de um peixe e os intervalos entre pulsos foram produzidos por diferentes distribuições: aleatória, intervalos gravados previamente do próprio ou de outro peixe, sequências manipuladas para repetir determinados trechos reais intercalados com trechos aleatórios, etc. Um segundo computador foi utilizado para detectar os instantes dos pulsos de estímulo e resposta e armazenar estas sequências em arquivos. Posteriormente utilizamos estas sequências para calcular a informação mútua média entre os sinais e verificamos que diferentes peixes reconhecem e reagem (alterando seus disparos elétricos) a determinados trechos da série de estímulo real de maneira bastante reprodutível. Também desenvolvemos outro programa de controle para detectar os pulsos do peixe em um dos aquários e estimular, em tempo real, o peixe de outro aquário e vice­versa. Assim, a única forma de interação entre os peixes é através dos pulsos elétricos e esta interação ocorre de modo bidirecional. Os dados destes experimentos também foram analisados utilizando o cálculo da informação mútua média entre os padrões dos dois peixes e encontramos evidências de que neste caso o fluxo de informação é maior que nos experimentos unidirecionais. Nosso aparato permitiu utilizar com sucesso a teoria da informação para estudar a dinâmica de disparo durante a interação elétrica entre peixes e possibilita diversos experimentos futuros em que pretendemos relacionar os padrões elétricos ao comportamento social dos animais e a sua interação com o meio ambiente. / We built an experimental apparatus to measure the electric organ discharge times from weakly electric fishes of the Gymnotus carapo species. Such fishes use these pulses to actively locate objects in water as well as in social communication. Our apparatus was designed to allow such measures in the absence of some external perturbations the fishes are sensitive to, such as mechanical vibrations, electric fields and changes in the laboratory luminosity. A set of eight electrods were installed in the corners of the experimental tank and allows to obtain the discharge times without need to restrain the movements of the fish. Actually, from the maximal amplitudes of the discharge in different elecrodes we can infer the position and movements of the fish and relate its electrical dynamics to its behavior. A computer program (C language) was written to use a digital to analog interface to reproduce the time series of a discharge pulse from a real fish (recorded previously) and this electrical signal was used to stimulate the animals. The artificial pulses were applied to an electrical dipole built to mimic the geometry of the electrical organ of a living fish. The intervals between discharges were chosen from sequences obtained from different distributions: random, sequencies from real living fishes, handled sequencies where we repeated some real patterns with random patterns in between, etc. The detection of the stimuli and response pulses were done in another computer with the software Dasylab and the discharge times sequencies were recorded in harddisk for further analysis. Both sequencies were used to compute the average mutual information between the signals and we verified that different fishes recognize and react (changing their pulse interval pattterns) to the same regions of the real stimuli sequence. We also developed another control program (C language) to detect the discharges of a fish in one tank and to stimulate, in real time, a fish in another tank with those pulses, and vice­versa, in a bidirectional way. In this way, the only interaction between the fishes is through their electric pulses. The data analysis also consisted in obtaining the average mutual information between the sequencies of the two fishes and we found evidences that the flow of information is higher than that found in unidirectional experiments. Our apparatus allowed us to succesfully apply information theory to study the dynamics of the discharge intervals when the fishes are interacting. In the future we intend to extensivelly use such experiments to relate the electrical patterns to social behavior and to the interaction of these fishes with their environment.