Fighting and Stinging Responses are Affected by a Dopamine Receptor Blocker Flupenthixol in Honey Bee Virgin Queens

Fighting and aggression are important tasks for self-preservation in animals. In honey bees, virgin queens fight against each other for survival in a monogynous colony. Because the virgin queens have higher levels of dopamine (DA) in the brain than do mated queens with low aggressiveness, DA may promote fighting and aggression behaviours of virgin queens. In the present study, we investigated the effect of DA on the fighting and stinging response of honey bee virgin queens. We injected two concentrations (10 −3 M and 10 −2 M) of DA and the DA receptor blocker flupenthixol into the abdomen of one-day-old virgin queens and observed fighting and stinging responses. DA injection did not affect fighting and stinging. Injections of 10 −3 M flupenthixol decreased the winning rate significantly, whereas 10 −2 M flupenthixol increased the winning rate, indicating the opposite effects on fighting responses depending on the degrees of blockade of DA signalling. In terms of the stinging response, 10 −2 M flupenthixol-injected virgin queens stung significantly more often than control and 10 −3 M flupenthixol-injected virgin queens. These results suggest an involvement of DA signalling in the regulation of fighting and aggression in virgin queens, although a blockade of DA does not always inhibit these behaviours.