Agonistic behavior and fear response during consecutive encounters in female fish

While consecutive agonistic encounters modulating aggressive behavior are well studied in males, the extent to which social behavior can be altered by fear sensing during consecutive agonistic encounters remains unexplored. A well-established paradigm to assess fear sensing is the exposure to alarm substances (AS) from conspecifics in Ostariophysi fish, such as zebrafish, which causes several physiological and behavioral changes associated to distress. Considering that the exposure to AS induces changes in individual behavior associated to fear response, the aim of the present work is to examine whether repeated exposure to AS alters both agonistic behavior and fear response in female zebrafish. Moreover, since female aggression is understudied when compared to males, this study also assesses possible differences according to the reproductive stage. We performed intrasexual dyadic encounters between female zebrafish to determine if agonistic behavior is altered during two consecutive contests and by the presence of AS. When comparing agonistic behavior in different reproductive stages, results suggest there are no differences in latency and in freezing. Regarding time of aggression, while there are no differences between contests in prespawning or postspawning, significant differences are detected between postspawning dyads and mixed dyads with both females in different reproductive stages. Results suggest that exposure to AS reduces female motivation to engage in an agonistic encounter while aggressive behavior is still maintained despite sensing AS as potential threat, regardless of corresponding to the first or second contest. Finally, similar to agonistic behavior, the effect of fear sensing on individual behavioral parameters such as distance, mean velocity and freezing is also observed during a first and also a second exposure to AS. To the best of our knowledge, this is the first evidence assessing how consecutive agonistic encounters with a real opponent can be altered by repeated exposure to AS.