Venn diagram depicting the number of hub genes identified for CO2 treatment and behavioural traits in the CNS and eyes. The yellow Venn diagram in the centre depicts the number of hub genes for CO2 treatment that are CNS-specific (left) and eyes-specific (right), and the overlap represents the number of CO2 treatment hub genes shared by both tissues. CNS-specific and eyes-specific CO2 treatment hub genes also identified as a hub gene for one or more behavioural traits in the CNS or eyes are on the left and right, respectively. Hub genes for CO2 treatment found in both tissues, that are also a hub gene for a behavioural trait in one or both tissues, are shown at the bottom centre. CO2 treatment hub genes shared with activity traits (active time, distance and speed) and exploratory conspecific-directed behaviours (number of exploratory interactions and whether any exploratory interactions occurred) are in blue and grey, respectively. Exploratory interaction? = whether any exploratory interactions occurred (yes/no).