Developmental social experience of parents affects behaviour of offspring in zebrafish

Interactions between conspecifics early in life have the potential to shape phenotypic differences between individuals. These changes in phenotype may subsequently be passed to future offspring, something that has been studied in live-bearing mammals where there is often an element of parental care. The present study considers the transgenerational effects of social environment in zebrafish, Danio rerio, an egg-laying animal that shows no parental care, thus removing any influence of parental interaction and allowing the effects of conspecific interaction to be clearly determined. Zebrafish (F0) were reared from fertilization to reproduction in three different social treatments: isolation, groups of 30 or groups of 100. At 28 days post fertilization, individuals were tested for anxiety and activity and at 3 months old for aggression. These F0 fish were raised to sexual maturity and bred within their treatment group. The F1 generation were then raised in groups of 30, irrespective of parental social environment and were assessed for behaviour in the same way as their parents. Social isolation increased anxiety and decreased aggression in the F0 fish compared to those raised in social groups of 100. F0 fish raised in social groups of 30 showed an intermediate response. Differences in anxiety were not passed to the F1 generation; however, offspring of socially isolated fish were less aggressive than offspring of parents from social groups of 30 and 100. The social environment that an individual experienced from fertilization to reproduction affected their own behaviour and the behaviour of their offspring.