The effects of serotonin, dopamine, octopamine and tyramine on behavior of workers of the ant Formica polyctena during dyadic aggression tests.

We investigated the effect of injections of four biogenic amines (serotonin, dopamine, octopamine and tyramine) on behavior patterns displayed by workers of the red wood ant Formica polyctena during dyadic confrontations with four types of opponents: a nestmate, an alien conspecific, an allospecific ant (Formica fusca), and a potential prey, a nymph of the house cricket (Acheta domesticus). Significant effects of biogenic amine administration were observed almost exclusively in the case of confrontations with allospecific opponents. Serotonin treatment exerted stimulatory effects on behavior patterns involving physical aggression (biting accompanied by gaster flexing, dragging and formic acid spraying), but these effects were relatively weak and/or documented by indirect evidence. Dopamine administration exerted a stimulatory effect on open-mandible threats directed by F. polyctena to F. fusca and to cricket nymphs, and on biting behavior directed to cricket nymphs. Surprisingly, octopamine treatment did not exert significant effects on aggressive behavior of the tested ants. Tyramine administration exerted a suppressing effect on threatening behavior directed to F. fusca, but led to shortening of the latencies to the first open-mandible threat during the tests with cricket nymphs. Biogenic amine administration also influenced non-aggressive behavior of the tested ants. Our findings confirmed the role of serotonin and dopamine in the mediation of ant aggressive behavior and documented for the first time significant effects of tyramine treatment on ant aggressive behavior. We also demonstrated that not only specific patterns of ant aggressive behavior, but also behavioral effects of biogenic amine treatments are as a rule strongly context-dependent.