Fig. 6. Combined serotonin levels in various areas in the brains of juvenile lobsters. The levels of serotonin in all the accessory lobes (ALs; black), olfactory lobes (OLs; dark gray) and brain remainders (light gray) are added together for each of the six time points (data from Fig. 5A–C). As in the whole-brain studies (Fig. 3), the pre-dusk peak is the most pronounced feature. Comparisons of the changes in serotonin content in individual brain areas at the pre-dusk peak (11:00 h compared with 15:00 h) show that serotonin levels in the ALs rise by 18%, the OLs by 123% and the brain remainder by 197% during this period.