Agonistic interactions elicit rapid changes in brain nonapeptide levels in zebrafish

The teleost fish nonapeptides, arginine vasotocin (AVT) and isotocin (IT), have been implicated in the regulation of social behavior. These peptides are expected to be involved in acute and transient changes in social context, in order to be efficient in modulating the expression of social behavior according to changes in the social environment. Here we tested the hypothesis that short-term social interactions are related to changes in the level of both nonapeptides across different brain regions. For this purpose we exposed male zebrafish to two types of social interactions: (1) real opponent interactions, from which a Winner and a Loser emerged; and (2) mirror-elicited interactions, that produced individuals that did not experience a change in social status despite expressing similar levels of aggressive behavior to those of participants in real-opponent fights. Non-interacting individuals were used as a reference group. Each social phenotype (i.e. Winners, Losers, Mirror-fighters) presented a specific brain profile of nonapeptides when compared to the reference group. Moreover, the comparison between the different social phenotypes allowed to address the specific aspects of the interaction (e.g. assessment of opponent aggressive behavior vs. self-assessment of expressed aggressive behavior) that are linked with neuropeptide responses. Overall, agonistic interactions seem to be more associated with the changes in brain AVT than IT, which highlights the preferential role of AVT in the regulation of aggressive behavior already described for other species.

The importance of novelty: Male–female interactions among blue-black grassquits in captivity

Mate choice is a primary mechanism driving the evolution of sexually selected traits such as elabo-rate displays and ornaments. In a majority of taxa studied to date, females are seen to actively sampleand evaluate multiple males, presumably to optimize mating opportunities. During this process femalesmay encounter males both familiar and novel, a distinction that might influence how mate choice pro-ceeds. Using a socially monogamous passerine, the blue-black grassquit (Volatinia jacarina), we studiedhow females respond to novel versus familiar (“paired”) males, and how encounters with novel malesinfluence subsequent interactions with their paired males. Additionally, we measured the hormonalresponse of males after visualizing their paired females interacting with novel males. We found thatfemales were attentive to novel males irrespective of these males’ phenotypic attributes, suggesting thatin these interactions novelty is highly relevant. After exposure to novel males, females tended to respondaggressively towards their paired males; by contrast, the behaviour of males towards their paired femalesdid not change. Moreover, we did not detect any hormonal responses of males to viewing their pairedfemales interacting with novel males. Together these results suggest that the distinction between famil-iarity and novelty may hold special relevance for females in mate choice, a finding that bears upon ourunderstanding of the evolution of extra-pair paternity and reproductive behaviour.

Quantifying aggressive behavior in zebrafish

Aggression is a complex behavior that influences social relationships and can be seen as adaptive or maladaptive depending on the context and intensity of expression. A model organism suitable for genetic dissection of the underlying neural mechanisms of aggressive behavior is still needed. Zebrafish has already proven to be a powerful vertebrate model organism for the study of normal and pathological brain function. Despite the fact that zebrafish is a gregarious species that forms shoals, when allowed to interact in pairs, both males and females express aggressive behavior and establish dominance hierarchies. Here, we describe two protocols that can be used to quantify aggressive behavior in zebrafish, using two different paradigms: (1) staged fights between real opponents and (2) mirror-elicited fights. We also discuss the methodology for the behavior analysis, the expected results for both paradigms, and the advantages and disadvantages of each paradigm in face of the specific goals of the study.

A expressão da depressão e da psicose no desenho infantil na fase da latência

Dissertação de Mestrado apresentada ao Instituto Superior de Psicologia Aplicada para obtenção de grau de Mestre na especialidade de Psicologia Clínica.

“O Prazer de não sentir”: Experiência vivida pelos agressores sexuais

Dissertação de Mestrado apresentada ao ISPA - Instituto Universitário