The role of dopamine in foraging decisions in social insects

Abstract

Animals often need to make decisions about whether to confront risks, and climate change is making these decisions even more critical by increasing environmental stress. Biogenic amines are crucial for modulating behavior in all animals and may contribute to behavioral adaptations to changing environments through supporting decision-making involving risk. Our review focuses on the neuromodulator dopamine in insects because of its role in risk-related behavioral choices, particularly in the context of ant foraging activity. In ants, individual decisions contribute to the collective regulation of foraging activity. We consider the role of dopamine in the regulation of collective foraging activity to manage water loss in the desert red harvester ant, Pogonomyrmex barbatus, in the southwest US that is undergoing severe drought. We discuss dopaminergic circuitry and its involvement in decisions about foraging risk, drawing from both the vertebrate and invertebrate literature, to outline areas of future research in the role of dopamine in collective decision-making in response to changing environmental conditions.

Keywords: ant; decision-making; dopamine; foraging; insect.

Figure 1

A harvester ant forager decides whether to leave the nest on another foraging trip by using its rate of antennal contact with returning foragers with food. During antennal contact, the forager assesses the odor of the cuticular hydrocarbons of the other ant, and the odor of the food it is carrying. Foragers lose water to evaporation when outside the nest. Dry conditions and desiccation experienced on previous foraging trips inhibit the decision to leave on another foraging trip. Dopamine (DA) overrides the forager’s assessment of the risk due to dry conditions.

Figure 2

Main dopaminergic clusters mapped in (A) the fruit fly Drosophila melanogaster, (B) the honey bee Apis mellifera, and (C) the Indian jumping ant Harpegnathos saltator. Only one hemisphere of the brain is labeled. Expected homologous clusters are shown in the same color across species in (A, B). Clusters are indicated with black letters and arrows, while functionally distinct brain regions are labeled in grey. In (C), a confocal micrograph shows dopamine immunoreactivity in green, with brain regions visualized using propidium iodide-labeled nuclei in magenta. MB, Mushroom body; CC, central complex; AL, antennal lobe; OL, optic lobe and SEZ, subesophageal zone. Scale bars: 200 µm (A, B); 500 µm (C). Source: (A, B) adapted from Tedjakumala et al. (112), published under CC BY 4.0; (C) adapted with permission from Hoyer et al. (113), © 2005 Elsevier Ltd.