A classe Chondrichthyes é representada por animais de esqueleto cartilaginoso e calcificação prismática. Eles são divididos em duas subclasses, Elasmobranchii (tubarões e raias) e Holocephali (quimeras), que têm uma história evolutiva de mais de 400 milhões de anos. Devido à grande adaptabilidade destes animais em diferentes habitats, eles desenvolveram sofisticadas habilidades sensoriais, como os sistemas mecanorreceptor da linha lateral e eletrossensorial. A maior ordem de tubarões, a Carcharhiniformes tem a maioria dos representantes ocorrendo no Brasil. Entre eles, destacamos o tubarão-azul (Prionace glauca), pelágico oceânico, espécie de grande porte e cosmopolita, e um pequeno tubarão pelágico costeiro, o tubarão-frango (Rhizoprionodon lalandii), representantes dessa ordem com grande importância econômica pela sua pesca. Dada a diversidade morfológica e funcional dos sistemas sensoriais, em resposta a variações ecológicas e filogenéticas, o objetivo deste estudo foi descrever as estruturas morfológicas da linha lateral e das ampolas de Lorenzini, os dentículos dérmicos e os nervos associados à elas, em P. glauca e R. lalandii, utilizando documentação textual e fotográfica de estruturas macroscópicas, e métodos de microscopia, como microscopias de luz, eletrônica e imunofluorescência. Histologicamente, o neuromasto, principal unidade celular da linha lateral mostrou-se semelhante em ambas as espécies, e em P. glauca, esta célula foi encontrada desde o período intra-uterino. Em P. glauca, foi relatado um novo tipo de canal sensorial associado à linha lateral. A ampola de Lorenzini de R. lalandii revelou-se mais organizada do que em P. glauca, devido à quantidade e estruturação dos alvéolos. Os dentículos dérmicos de R. lalandii são mais especializados em várias regiões, particularmente as que envolvem os poros sensoriais. Em relação às características microscópicas dos nervos, eles se assemelham estruturalmente aos dos vertebrados superiores. Para a imunofluorescência, a colocalização foi realizada por tripla marcação dos núcleos dos nervos (DAPI), com receptor de membrana (P2X7), fibras inibidoras (NOS) e células gliais (GFAP), nos nervos da linha lateral e oftálmico superficial. Em ambas as espécies, a distribuição dos nervos foi uniforme. Em suma, as características estudadas em P. glauca são muito semelhantes às encontradas em R. lalandii, no entanto, devido ao hábito da vida oceânica, outras estratégias sensoriais seriam mais relevantes para a sua sobrevivência neste ambiente. As características microscópicas de R. lalandii demonstraram a relação adaptativa com a ecologia da espécie. Seu estilo de vida costeiro demonstrou maior especialização em certos sistemas sensoriais, contribuindo para melhor adaptação em determinados ambientes, uma vez que a morfologia e a organização dos sistemas sensoriais estão diretamente ligadas ao estilo de vida dos indivíduos. / The class of Chondrichthyes is represented by animals with cartilaginous skeleton with prismatic calcification. They are divided into two subclasses, Elasmobranchii (sharks, skates and rays) and Holocephali (chimaeras), which have an evolutionary history of more than 400 million years. Due to their great adaptability in different habitats, they have developed sophisticated sensorial abilities, such as mechanosensory lateral line and electrosensory systems. The largest order of sharks, the Carcharhiniformes has most of the representatives in Brazil. Among them, we highlight the blue shark (Prionace glauca), oceanic pelagic, large and cosmopolitan specie, and a small coastal pelagic shark, the sharpnose shark (Rhizoprionodon lalandii), species with economical importance. Given the morphological and functional diversity of sensory systems, in response to ecological and phylogenetic variations, the aims of this study is to describe the morphological structures of the lateral line and ampullae of Lorenzini, the dermal denticles and nerves associated with them, in P. glauca and R. lalandii, using textual and photographic documentation of macroscopic structures, and microscopic methods, such as light and electronic microscopies and immunofluorescence. Histologically, the neuromast, main cell unit of lateral line system was similar in both species, and in P. glauca, this cell was found since the intrauterine period. In P. glauca, a new type of sensorial canal associated with the lateral line was reported. The ampullae of Lorenzini of R. lalandii proved to be more organized than in P. glauca, because of the amount and structure of the alveoli. The dermal denticles in R. lalandii were more specialized in various regions, particularly those involving sensory pores. Regarding the microscopic characteristics of the nerves, they resemble structurally to the superior vertebrates. For immunofluorescence, the colocalization was performed by triple labeling the nuclei (DAPI) of the nerves, with a membrane receptor (P2X7), inhibitory fibers (NOS) and glial cells (GFAP) in lateral line and superficial ophthalmic nerves. In both species, the distribution of nerves was uniform. In short, the characteristics studied in P. glauca are very similar to those found in R. lalandii, however, due to the habit of oceanic life, other sensory strategies are most relevant to their survival in this environment. Microscopic features of R. lalandii demonstrated the adaptive relationship with the ecology of the species. Its coastal way of life showed greater specialization in certain sensory and attachments systems, contributing to better adapt in certain environments, since the morphology and organization of sensory systems are directly linked to the lifestyle of individuals.

A classe Chondrichthyes é representada por animais de esqueleto cartilaginoso e calcificação prismática. Eles são divididos em duas subclasses, Elasmobranchii (tubarões e raias) e Holocephali (quimeras), que têm uma história evolutiva de mais de 400 milhões de anos. Devido à grande adaptabilidade destes animais em diferentes habitats, eles desenvolveram sofisticadas habilidades sensoriais, como os sistemas mecanorreceptor da linha lateral e eletrossensorial. A maior ordem de tubarões, a Carcharhiniformes tem a maioria dos representantes ocorrendo no Brasil. Entre eles, destacamos o tubarão-azul (Prionace glauca), pelágico oceânico, espécie de grande porte e cosmopolita, e um pequeno tubarão pelágico costeiro, o tubarão-frango (Rhizoprionodon lalandii), representantes dessa ordem com grande importância econômica pela sua pesca. Dada a diversidade morfológica e funcional dos sistemas sensoriais, em resposta a variações ecológicas e filogenéticas, o objetivo deste estudo foi descrever as estruturas morfológicas da linha lateral e das ampolas de Lorenzini, os dentículos dérmicos e os nervos associados à elas, em P. glauca e R. lalandii, utilizando documentação textual e fotográfica de estruturas macroscópicas, e métodos de microscopia, como microscopias de luz, eletrônica e imunofluorescência. Histologicamente, o neuromasto, principal unidade celular da linha lateral mostrou-se semelhante em ambas as espécies, e em P. glauca, esta célula foi encontrada desde o período intra-uterino. Em P. glauca, foi relatado um novo tipo de canal sensorial associado à linha lateral. A ampola de Lorenzini de R. lalandii revelou-se mais organizada do que em P. glauca, devido à quantidade e estruturação dos alvéolos. Os dentículos dérmicos de R. lalandii são mais especializados em várias regiões, particularmente as que envolvem os poros sensoriais. Em relação às características microscópicas dos nervos, eles se assemelham estruturalmente aos dos vertebrados superiores. Para a imunofluorescência, a colocalização foi realizada por tripla marcação dos núcleos dos nervos (DAPI), com receptor de membrana (P2X7), fibras inibidoras (NOS) e células gliais (GFAP), nos nervos da linha lateral e oftálmico superficial. Em ambas as espécies, a distribuição dos nervos foi uniforme. Em suma, as características estudadas em P. glauca são muito semelhantes às encontradas em R. lalandii, no entanto, devido ao hábito da vida oceânica, outras estratégias sensoriais seriam mais relevantes para a sua sobrevivência neste ambiente. As características microscópicas de R. lalandii demonstraram a relação adaptativa com a ecologia da espécie. Seu estilo de vida costeiro demonstrou maior especialização em certos sistemas sensoriais, contribuindo para melhor adaptação em determinados ambientes, uma vez que a morfologia e a organização dos sistemas sensoriais estão diretamente ligadas ao estilo de vida dos indivíduos. / The class of Chondrichthyes is represented by animals with cartilaginous skeleton with prismatic calcification. They are divided into two subclasses, Elasmobranchii (sharks, skates and rays) and Holocephali (chimaeras), which have an evolutionary history of more than 400 million years. Due to their great adaptability in different habitats, they have developed sophisticated sensorial abilities, such as mechanosensory lateral line and electrosensory systems. The largest order of sharks, the Carcharhiniformes has most of the representatives in Brazil. Among them, we highlight the blue shark (Prionace glauca), oceanic pelagic, large and cosmopolitan specie, and a small coastal pelagic shark, the sharpnose shark (Rhizoprionodon lalandii), species with economical importance. Given the morphological and functional diversity of sensory systems, in response to ecological and phylogenetic variations, the aims of this study is to describe the morphological structures of the lateral line and ampullae of Lorenzini, the dermal denticles and nerves associated with them, in P. glauca and R. lalandii, using textual and photographic documentation of macroscopic structures, and microscopic methods, such as light and electronic microscopies and immunofluorescence. Histologically, the neuromast, main cell unit of lateral line system was similar in both species, and in P. glauca, this cell was found since the intrauterine period. In P. glauca, a new type of sensorial canal associated with the lateral line was reported. The ampullae of Lorenzini of R. lalandii proved to be more organized than in P. glauca, because of the amount and structure of the alveoli. The dermal denticles in R. lalandii were more specialized in various regions, particularly those involving sensory pores. Regarding the microscopic characteristics of the nerves, they resemble structurally to the superior vertebrates. For immunofluorescence, the colocalization was performed by triple labeling the nuclei (DAPI) of the nerves, with a membrane receptor (P2X7), inhibitory fibers (NOS) and glial cells (GFAP) in lateral line and superficial ophthalmic nerves. In both species, the distribution of nerves was uniform. In short, the characteristics studied in P. glauca are very similar to those found in R. lalandii, however, due to the habit of oceanic life, other sensory strategies are most relevant to their survival in this environment. Microscopic features of R. lalandii demonstrated the adaptive relationship with the ecology of the species. Its coastal way of life showed greater specialization in certain sensory and attachments systems, contributing to better adapt in certain environments, since the morphology and organization of sensory systems are directly linked to the lifestyle of individuals.

A stochastic leaky integrate-and-fire neuron model was implemented in this study to simulate the spiking activity of the electrosensory "P-unit" receptor neurons of the weakly electric fish Apteronotus leptorhynchus. In the context of sensory coding, these cells have been previously shown to respond in experiment to natural random narrowband signals with either a linear or nonlinear coding scheme, depending on the intrinsic firing rate of the cell in the absence of external stimulation. It was hypothesised in this study that this duality is due to the relation of the stimulus to the neuron's excitation threshold. This hypothesis was validated with the model by lowering the threshold of the neuron or increasing its intrinsic noise, or randomness, either of which made the relation between firing rate and input strength more linear. Furthermore, synchronous P-unit firing to a common input also plays a role in decoding the stimulus at deeper levels of the neural pathways. Synchronisation and desynchronisation between multiple model responses for different types of natural communication signals were shown to agree with experimental observations. A novel result of resonance-induced synchrony enhancement of P-units to certain communication frequencies was also found.

A stochastic leaky integrate-and-fire neuron model was implemented in this study to simulate the spiking activity of the electrosensory "P-unit" receptor neurons of the weakly electric fish Apteronotus leptorhynchus. In the context of sensory coding, these cells have been previously shown to respond in experiment to natural random narrowband signals with either a linear or nonlinear coding scheme, depending on the intrinsic firing rate of the cell in the absence of external stimulation. It was hypothesised in this study that this duality is due to the relation of the stimulus to the neuron's excitation threshold. This hypothesis was validated with the model by lowering the threshold of the neuron or increasing its intrinsic noise, or randomness, either of which made the relation between firing rate and input strength more linear. Furthermore, synchronous P-unit firing to a common input also plays a role in decoding the stimulus at deeper levels of the neural pathways. Synchronisation and desynchronisation between multiple model responses for different types of natural communication signals were shown to agree with experimental observations. A novel result of resonance-induced synchrony enhancement of P-units to certain communication frequencies was also found.

A stochastic leaky integrate-and-fire neuron model was implemented in this study to simulate the spiking activity of the electrosensory "P-unit" receptor neurons of the weakly electric fish Apteronotus leptorhynchus. In the context of sensory coding, these cells have been previously shown to respond in experiment to natural random narrowband signals with either a linear or nonlinear coding scheme, depending on the intrinsic firing rate of the cell in the absence of external stimulation. It was hypothesised in this study that this duality is due to the relation of the stimulus to the neuron's excitation threshold. This hypothesis was validated with the model by lowering the threshold of the neuron or increasing its intrinsic noise, or randomness, either of which made the relation between firing rate and input strength more linear. Furthermore, synchronous P-unit firing to a common input also plays a role in decoding the stimulus at deeper levels of the neural pathways. Synchronisation and desynchronisation between multiple model responses for different types of natural communication signals were shown to agree with experimental observations. A novel result of resonance-induced synchrony enhancement of P-units to certain communication frequencies was also found.

A stochastic leaky integrate-and-fire neuron model was implemented in this study to simulate the spiking activity of the electrosensory "P-unit" receptor neurons of the weakly electric fish Apteronotus leptorhynchus. In the context of sensory coding, these cells have been previously shown to respond in experiment to natural random narrowband signals with either a linear or nonlinear coding scheme, depending on the intrinsic firing rate of the cell in the absence of external stimulation. It was hypothesised in this study that this duality is due to the relation of the stimulus to the neuron's excitation threshold. This hypothesis was validated with the model by lowering the threshold of the neuron or increasing its intrinsic noise, or randomness, either of which made the relation between firing rate and input strength more linear. Furthermore, synchronous P-unit firing to a common input also plays a role in decoding the stimulus at deeper levels of the neural pathways. Synchronisation and desynchronisation between multiple model responses for different types of natural communication signals were shown to agree with experimental observations. A novel result of resonance-induced synchrony enhancement of P-units to certain communication frequencies was also found.