Agonistic Behavior and Fear Response During Consecutive Encounters in Female Fish

ABSTRACT 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 with distress. Although exposure to AS has been increasingly used to study various aspects related to threat perception, the general effect of fear sensing on agonistic behavior is understudied. Interestingly, 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. The aim of the present work is to examine whether fear sensing after two consecutive exposures to AS alters agonistic behavior 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. To control for the biological effect of the AS, individual behavioral parameters such as distance, mean velocity and freezing were determined during a first and a second exposure to AS. We then quantified agonistic behaviors during dyadic encounters, such as the latency to the first aggressive display, freezing (a well‐established behavior associated with fear response after one acute AS exposure) and time of aggression, as the total time in which opponents engage in agonistic interaction. 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 a potential threat, regardless of corresponding to the first or second contest. 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.