Ambiente social: influência de coespecíficos na modulação do estresse e comportamento agressivo em peixes
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Data
2019-08-02
Autores
Rossi, Vanessa Stramantinoli [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Esta tese tem como objetivo principal avaliar como o ambiente social afeta a recuperação do estresse e o comportamento agressivo em peixes. Primeiramente nosso foco foi avaliar se havia influências sociais positivas após a aplicação de estresse ao ponto da obtenção/geração de uma recuperação mais rápida, amenizando o estresse em indivíduos espectadores. Este fenômeno é conhecido como apoio social (social buffering) e já é descrito em diversos animais sociais, desde mamíferos, peixes e até invertebrados. Em peixes, este foi estudado em Zebrafish, que é uma espécie que possui semelhanças genéticas e neurais com vertebrados superiores e apresenta estrutura social bem definida. Apesar disso, esse fenômeno ainda é pouco estudado em outras espécies com características sociais específicas, como por exemplo, sociedades com presença de altas taxas de agressão e disputa hierárquica entre indivíduos. Dessa forma, avaliamos a ocorrência do apoio social em tilápia-do-Nilo, uma espécie territorialista com agressividade elevada entre os indivíduos para manutenção de hierarquia. Neste estudo, observamos a ocorrência do fenômeno de apoio social apenas no contexto em que o indivíduo era inserido em um ambiente novo e possuía sinais visuais de grupos dos coespecíficos. Entretanto, ao longo da experimentação, após a familiarização com os coespecíficos, notamos o aparecimento de outro fenômeno que influenciou negativamente na recuperação do estresse, o ‘estresse social’. Este é um fenômeno causado por interações agonísticas em um grupo e, neste trabalho, ocorreu mesmo em indivíduos isolados fisicamente, possuindo apenas sinais visuais do grupo social. Assim, decidimos avaliar se haveria influência da observação de interações agressivas de um grupo no comportamento agressivo de indivíduos espectadores. Obtivemos uma correlação negativa, em que, quanto menor o número de confrontos de um grupo, maior a agressividade deflagrada pelo espectador. Como nesse estudo não foi possível o controle das interações dos grupos sociais, decidimos realizar um novo estudo onde havia este controle. Dessa forma, em nosso segundo estudo, avaliamos se o comportamento agressivo de indivíduos espectadores é modulado a partir do nível de agressão do grupo observado. Com isso, observamos uma resposta similar, na qual, animais que presenciaram coespecíficos sem interações agressivas, aumentaram os níveis de agressividade quando comparado a um controle. Assim, concluímos que mesmo em uma espécie agressiva como a tilápia-do-Nilo, com o predomínio de estresse social, há a ocorrência de apoio social em determinado contexto. Além disso, a tilápia é capaz de avaliar o contexto agressivo social, que por sua vez modula a agressividade individual.
This thesis aims to evaluate how the social environment affects stress recovery and aggressive behavior in fish. Firstly our focus was to evaluate if there were positive social influences after stress application with a faster stress recovery or mitigation in bystander individuals. This phenomenon is known as social buffering and is already described in many social animals, as mammals, fish and invertebrates. In fish, the phenomenon has been studied in Zebrafish, which is a species that has genetic and neural similarities to higher vertebrates and has well-defined social structure. Nevertheless, this is still poorly studied in other species with specific social characteristics, such as in high agressive groups with hierarchical dispute between individuals. Thus, we evaluated the occurrence of social support in Nile tilapia, a territorialist species with high aggressiveness among individuals to maintain hierarchy. In this study, we observed the occurrence of the social support phenomenon only in the context in which the individual was inserted in a new environment and had visual signals from co-specific groups. However, throughout experimentation, after familiarization with the co-specifics, we noticed the appearance of another phenomenon that negatively influenced the recovery of stress, the 'social stress'. This is a phenomenon caused by agonistic interactions in a group and, in this work, occurred even in physically isolated individuals, that had only visual signs of the social group. Thus, we decided to evaluate if there would be influence of the observation of aggressive interactions of a group in the aggressive behavior of bystander individuals. We obtained a negative correlation, in which, the smaller the number of confrontations of a group, the greater the aggression unleashed by the bystander. As in this study it was not possible to control the interactions of social groups, we decided to conduct a new study where there was this control. Thus, in our second study, we evaluated whether the aggressive behavior of bystander individuals is modulated from the aggression level of the observed group. Thus, we observed a similar response in which animals that witnessed co-specifics without aggressive interactions increased levels of aggressiveness when compared to a control. Thus, we conclude that even in an aggressive species such as Nile tilapia, with the predominance of social stress, there is social support in a given context. In addition, tilapia is able to assess the aggressive social context, and it modulates individual aggressiveness.
This thesis aims to evaluate how the social environment affects stress recovery and aggressive behavior in fish. Firstly our focus was to evaluate if there were positive social influences after stress application with a faster stress recovery or mitigation in bystander individuals. This phenomenon is known as social buffering and is already described in many social animals, as mammals, fish and invertebrates. In fish, the phenomenon has been studied in Zebrafish, which is a species that has genetic and neural similarities to higher vertebrates and has well-defined social structure. Nevertheless, this is still poorly studied in other species with specific social characteristics, such as in high agressive groups with hierarchical dispute between individuals. Thus, we evaluated the occurrence of social support in Nile tilapia, a territorialist species with high aggressiveness among individuals to maintain hierarchy. In this study, we observed the occurrence of the social support phenomenon only in the context in which the individual was inserted in a new environment and had visual signals from co-specific groups. However, throughout experimentation, after familiarization with the co-specifics, we noticed the appearance of another phenomenon that negatively influenced the recovery of stress, the 'social stress'. This is a phenomenon caused by agonistic interactions in a group and, in this work, occurred even in physically isolated individuals, that had only visual signs of the social group. Thus, we decided to evaluate if there would be influence of the observation of aggressive interactions of a group in the aggressive behavior of bystander individuals. We obtained a negative correlation, in which, the smaller the number of confrontations of a group, the greater the aggression unleashed by the bystander. As in this study it was not possible to control the interactions of social groups, we decided to conduct a new study where there was this control. Thus, in our second study, we evaluated whether the aggressive behavior of bystander individuals is modulated from the aggression level of the observed group. Thus, we observed a similar response in which animals that witnessed co-specifics without aggressive interactions increased levels of aggressiveness when compared to a control. Thus, we conclude that even in an aggressive species such as Nile tilapia, with the predominance of social stress, there is social support in a given context. In addition, tilapia is able to assess the aggressive social context, and it modulates individual aggressiveness.
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Palavras-chave
Comportamento social, Estresse, Agressividade, Peixe