Figure 5.

Physiological responses of the antennal lobe in workers and drones. (A) Calcium imaging recording (using bath-applied Calcium Green 2AM) in a worker bee. Upper left: upon odor delivery, a biphasic fluorescence signal is observed in active glomeruli, with a first fast positive component (max after ∼1 second), followed by a slow – highly spatially correlated – negative component (minimum after 8–10 seconds). Right: Odor activity maps, showing for each pixel in a false-color code the amplitude of the biphasic signal. General odors (1-hexanol and 2-octanol) and social pheromone (isopentyl acetate, IPA and citral) elicit combinatorial activity in the imaged glomeruli. Note that the glomeruli activated by the pheromones can be active in response to general odors and vice-versa. By contrast, no clear signals appeared with components of the queen mandibular pheromone (here 9-ODA and HVA). We believe the glomeruli responsible for processing of these signals are in other – yet unimaged – parts of the antennal lobe. (B) Calcium imaging recordings (using bath-applied Calcium Green 2AM) of antennal lobe activity in a drone bee. The odor activity maps are calculated as in (A). The position of the two accessible macroglomeruli is overlaid on the maps (white). General odors (here a complex blend, orange essential oil) and social pheromones (here geraniol) induce activity in ordinary-sized glomeruli, i.e., on the medio-ventral side of the antennal lobe. Interestingly, the major component of the queen mandibular pheromone, 9-ODA, which is involved in the attraction of males toward queens during nuptial flight, is specifically detected by the most voluminous macroglomerulus of the drone antennal lobe, MG2. By contrast, HVA, another QMP component whose role has only been proven in workers, induces activity in an ordinary-size glomerulus (for details, see Sandoz, 2006).