Chapter 15 - Octopamine and Tyramine Signaling in Locusts: Relevance to Olfactory Decision-Making

Abstract

Swarm-forming locusts are among the most favored subjects in the study of insect neurobiology and behavior. The migratory locust (Locusta migratoria) exhibits population-density-dependent transitional decision-making (attraction versus repulsion). Individual olfactory decision-making is essential in the phase polyphenism of locusts. Here, we summarize the progress of octopamine and tyramine signaling in locusts and discuss the relevance of these chemicals to olfactory decision-making in Locusta. Octopamine and its receptor α (OARα) can mediate olfactory attraction elicited by volatiles from gregarious locusts, whereas tyramine and its receptor (TAR) can modulate the repulsion response toward those volatiles. Octopamine–OARα and tyramine–TAR signaling antagonistically modulate the transitional olfactory decision-making during phase change, suggesting a seesaw manner utilized in this process. The seesaw mode by which these two signaling pathways function may provide vital clues to neurogenetic and neurophysiological mechanisms underlying individual olfactory decision-making.