Anatomical mapping and regulation of dopaminergic and octopaminergic neurons during temporal polyethism in the red harvester ant
Many social insects, such as ants, change their behavior stereotypically from nursing to foraging as they age, a concept known as temporal polyethism. Biogenic amines are associated with these specific behaviors, but much about them remains poorly understood in these animals. Many aminergic systems lack anatomical characterization, and little is known about the expression of genes required for the aforementioned behavioral phenotypes. Here, we studied Pogonomyrmex barbatus brains and identified the neurons that produce two relevant amines, dopamine and octopamine, by detecting their synthesis enzymes, tyrosine hydroxylase and tyramine beta-hydroxylase, and their transcripts. We also compared the expression of both genes in young nurses and mature foragers by measuring the fluorescence intensity. Dopaminergic and octopaminergic neurons are predominantly located in the protocerebrum and in the subesophageal zone. Neurons that produce dopamine are also present in the optic lobes, whereas octopamine-producing ones show clusters in the antennal lobes. Both genes are downregulated as the organism ages. A reduction in the expression of these genes might be correlated with the mature workers increased propensity to perform extranidal tasks, such as foraging.