Changes in the content of brain biogenic amine associated with early colony establishment in the Queen of the ant, Formica japonica

Abstract

We examined changes in the content of biogenic amines in the brains of ant queen associated with early colony establishment. In ants, including Formica japonica, winged virgin queens lose their wings following copulation, and then start establishing a colony. Significant changes in brain biogenic amine content in the queen are associated with transition from winged virgin queen to wingless mated queen. The levels of serotonin (5HT), octopamine (OA) and dopamine (DA) decreased significantly in the brain of the queen after starting a colony. On the other hand, tyramine (TA) increased significantly in the brain following colony establishment. Catabolized substances of the biogenic amines in the brain were also measured. The levels of N-acetyloctopamine (Nac-OA) and N-acetyltyramine (Nac-TA) in the brain did not show a significant change after the queen established a colony. However, the levels of N-acetylserotonin (Nac-5HT) in the brain were significantly higher in wingless mated queens than in winged virgin queens, whereas levels of N-acetyldopamine (Nac-DA) in the brain were significantly lower in wingless mated queens than winged virgin queens. These results suggest that serotonergic and octopaminergic systems in the brain of the queen change when the mated queen starts to establish a new colony.

Figure 1. Brain biogenic amines in the newly emerged queens (1 day old) and aged virgin queen (10 days old).

A: DA levels in the brain. Brain DA levels in the aged virgin queens were significantly higher than that in the newly emerged queens. B: OA levels in the brain. Brain OA levels in aged virgin queens were significantly higher than that in the newly emerged queens. C: TA levels in the brain. Brain TA levels in the aged virgin queens were significantly higher than that in the newly emerged queens. D: 5HT levels in the brain. Brain 5HT levels were significantly higher than that in the newly emerged queens. (*P<0.05, Student’s t-test).

Figure 2. Change in levels of DA and its related substances in the brain of queen associated with early colony establishment.

A: Change in level of DA in the brain of queen associated with early colony establishment. The level of DA in the brain of virgin queen was around 5 pmol/brain. The level of DA in the brain decreased significantly after a queen starts establishing a colony. B: The level of Nac-DA in the brain of queen. The level of Nac-DA in the brain significantly decreased after a queen starts establishing own colony. (*P<0.05, Student’s t-test).

Figure 3. Change in levels of OA and its related substances in the brain of queen associated with early colony establishment.

A: Change in level of TA in the brain of queen associated with early colony establishment. The content of TA in the brain was less than 0.5 pmol/brain. The level of TA in the brain increased significantly after a queen starts establishing own colony. B: The level of Nac-TA in the brain of queen. There was no significant change in the level of Nac-TA between winged virgin queen and wingless mated queen. C: Change in level of OA in the brain of queen associated with early colony establishment. The content of OA in the brain of virgin queen was about 1.5 pmol/brain. The level of OA in the brain decreased significantly after a queen starts establishing own colony. E: The level of Nac-OA in the brain of a queen. No significant change in the level of Nac-OA in the brain was observed between winged virgin queen and wingless mated queen. (*P<0.05, Student’s t-test).

Figure 4. Change in levels of 5HT and its related substances in the brain of queen associated with early colony establishment.

A: Change in level of 5HTP in the brain of queen associated with early colony establishment. 5HTP significantly decreased after queen started establishing a colony. B: Change in level of 5HT in the brain of queen associated with early colony establishment. 5HT significantly decreased after queen started establishing a colony. C: Change in level of Nac-5HT in the brain of queen associated with early colony establishment. Nac-5HT significantly increased after queen started establishing a colony. (*P<0.05, Student’s t-test).