The role of biogenic amines in the regulation of caste and dominance in colonies of the ant Harpegnathos saltator

The establishment of a reproductive hierarchy results from the outcome of physical contests coupled with internal changes in hormones and physiology. Biogenic amines, such as serotonin and dopamine, have been shown to underlie dominance interactions in species that range from mammals to insects. In the ant Harpegnathos saltator, workers engage in periodic tournaments over reproductive rights that are interspersed with long periods where the colony is stable and fighting is absent. We measured brain levels of biogenic amines in foragers, inside workers, and reproductive workers under stable colony conditions. Under a stable dominance hierarchy, subordinate workers do not reproduce, and physical policing is used to enforce subordinate sterility. Workers that begin to lay eggs in the presence of established gamergates are bit and held by their nestmates to inhibit ovarian development. We removed a group of workers from their colony so they would begin to activate their ovaries, and then returned them to their nest where they were policed. In these workers, we measured the change of biogenic amine levels in response to worker policing. Based on these experiments, we report how biogenic amines are involved in the regulation of reproduction and dominance in colonies of Harpegnathos saltator.