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FIGURE 1
Schematic diagram of the experimental design. (a) Enrichment treatments. Zebrafish larvae were randomly assigned to either “enrichment” or “no enrichment” treatment. As enrichment, Lego® bricks of various color and shape were provided to increase environmental complexity. Larvae were individually tested at different age according to the experimental schedule. Experiment 1 aimed at investigating the subjects’ reaction to a novel visual stimulus at three different ages: 7, 14, and 21 dpf. Experiment 2 aimed at investigating the subjects’ reaction at 7, 14, and 21 dpf to a novel odor. Experiment 3 aimed at investigating the effect of environmental enrichment duration and timing on subject's reaction to a novel object stimulus in 14‐dpf larvae exposed either from 4 to 6 dpf or from 11 to 13 dpf or not exposed to enrichment. (b) Behavioural apparatuses. Novel object test of experiments 1 and 3 (left): larvae were free to interact with a novel object (i.e., a black cone place over a white pedestal). Novel odor test of experiment 2 (right): larvae were free to explore undisturbed the two stimuli. One stimulus was soaked with a solution of FishWater and olfactory cue (Benzaldehyde), while the other had no olfactory cue and was used as control