Novel behavioural assays reveal sex-specific behavioural syndromes in anemonefish

Individual differences in behaviour and behavioural plasticity have been extensively studied in a variety of animals across the phylogenetic spectrum. Amphiprion species bring distinct insight into the topic because of their unique life history, mating system, and extraordinary degree of behavioural plasticity associated with protandrous (male-to-female) sex change. Several laboratory studies have begun characterizing individual differences in behaviour and behavioural plasticity in this species. The goals of this study were to expand the repertoire of behavioural assays available for Amphiprion ocellaris, establish repeatability of individual differences, identify sex differences, and explore whether individual differences in correlated behaviours can be detected consistently across experimental contexts (i.e., whether behavioural syndromes can be detected). We measured 35 behaviours across 7 behavioural assays in 9 reproductively active A. ocellaris pairs under 3 different reproductive contexts. Behaviours were repeatedly measured three separate times (rounds) over repeated spawning cycles. We found that 33 out of 35 behaviours were significantly individually repeatable across reproductive contexts and rounds. We found parental care, large intruder aggression, and female-oriented aggression assays produced the largest sex differences. Males performed 7-fold more egg care behaviours than females, whereas females performed significantly more aggressive behaviours toward a large heterospecific intruder (Dascyllus trimaculatus). Further, females displayed significantly more direct aggression toward a stimulus female than males. Three different behavioural syndromes were observed in males and none in females. These results expand our understanding of sex differences in behaviour and the division of labour in the iconic anemonefish. Future studies can use these assays to study the behaviour of fish in the middle of sex change or in the study of behavioural plasticity in this unique species.