It is commonly said that childhood experiences shape adult behaviour; that events that we may not even remember can have long-lasting, maybe even permanent effects. In a new article by scientists at the Champalimaud Centre for the Unknown in Portugal, published in Current Biology, experiments using zebrafish show that social experiences during the very first week of development impact behaviour at an early larval stage, before the fish are considered 'social'. This suggests that these experiences mark the fish much earlier than previously thought.
To discover how the behaviour of the fish would be affected by early social experience, zebrafish larvae were raised either in regular groups or alone in a dish. Then, high-speed video tracking was used to precisely measure swim movements while the fish were interacting. What was discovered surprised Antonia Groneberg, who was leading this project for her Ph.D. thesis: "It was previously thought that the effects of early-life social experience could only be seen at an age when the animal shows attraction to social stimuli, but we have shown that, in zebrafish, the effects can already be observed earlier. Normally, larvae move away from other close-by larvae, but we have found that larvae raised in isolation tend to react with a stronger escape swim, even when the other larvae are located at a larger distance. By removing inputs from different senses and testing artificial stimuli that mimic another fish, we found that isolation-raised fish showed stronger reactions to local water vibrations."
This project was also the basis for Groneberg's award-winning 'Dance your Ph.D.' video, which highlights the conclusions of this study through interpretative dance (featuring many members of the Champalimaud Research community!).
The next stages of this project involve the study of brain activity within these zebrafish. Larval zebrafish are transparent and therefore brain activity can be observed microscopically in ways that would be unthinkable in other vertebrate models. According to Michael Orger, responsible for the Vision to Action Lab and one of the Principal Investigators on the project, "Using live imaging, we can record activity throughout the whole brain, from areas that process sensory stimuli to those that control behaviour." Principal Investigator and head of the Collective Behaviour Lab Gonzalo de Polavieja added: "We are working towards a framework of collective behaviour in which we include the information on how the brain processes the information about the environment and about neighbouring conspecifics."
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Journal
Current Biology