Temporal patterns and sex differences in dyadic interactions in a wild zebrafish population

Male-female interactions in several group living organisms, including some fish species tend to be dynamic and play a key role in determining their mating and courtship behavior. Laboratory-bred zebrafish (Danio rerio) strains are one of the most widely used model systems in various fields of biology. While research on wild zebrafish behavior is gaining ground, our knowledge about their mating ecology and mating strategies is still limited. We investigated diel temporal patterns in inter-sex dyadic interactions among wild zebrafish and the occurrence of behavioral dimorphism in their interactive behaviors. We observed randomly paired male and female individuals at three distinct time intervals (early morning, morning and afternoon sessions) in the day and collected occurrence data for six discrete inter-individual interactive behaviors that were associated with mating, aggression, and display. We used generalized linear mixed models to examine the effect of time, sex of the individual and presence of oviposition substrate on these behavioral traits. We found a higher incidence of mating-associated behavior during the early parts of the day which declined by the afternoon. These mating-associated behaviors were also dependent on the presence of gravel substrate for egg-laying compared to other behaviors. This work is the first of its kind that details patterns in behavioral dimorphism between sexes in zebrafish. Our results throw light on the complex dynamics of male-female interactions in a group living externally fertilizing species and can have implications in designing experiments involving behavioral testing of zebrafish which is increasingly being done in toxicological studies and laboratory breeding.