Pheromone Deters Swarming Locusts from Cannibalism

Swarming migratory locusts – which threaten food security across the globe – avoid being eaten by other locusts by producing a smelly pheromone called phenylacetonitrile (PAN), according to a new study. The discovery of an anticannibalistic signaling pathway in locusts could provide a target for locust management strategies since cannibalistic interactions among locusts have been implicated in creation of swarms, which are highly destructive. A wide range of species practice cannibalism, mostly to supplement nutrition. This has led to the evolution of diverse anticannabalistic strategies to protect individuals from being eaten by their conspecifics. Although these dynamics can play an important ecological role, anticannabalistic strategies generally remain poorly understood. Among species of locusts, cannibalism is common, and cannibalistic interactions have been implicated in the formation and maintenance of damaging swarms. Hetan Chang et al. investigated the cannibalistic ecology of the migratory locust (Locusta migratoria) and found that they produce an anticannabalistic pheromone PAN that deters cannibalism when swarming. In juvenile locusts, Chang et al. discovered that when the population density increased, individual locusts began to produce PAN, which had an effect of protecting them from being eaten by another locust. The authors also discovered the underlying olfactory receptor responsible for detecting PAN and the signaling pathway responsible for driving aversion to cannibalistic behavior. Locust models engineered so they couldn't produce PAN lost its protective signal and were eaten far more often by conspecifics. What's more, locusts without functioning PAN olfactory receptors did not exhibit aversion to cannibalizing locusts producing PAN. "The work of Chang et al. serves as an important step in understanding the mechanisms that mediate the intricate balance between aggression and competition in locusts," write Iain Couzin and Einat Couzin-Fuchs in a related Perspective. "Because the PAN pathway regulates cannibalistic interactions, which in turn can drive mass migration, it may also prove to be a promising target for the future development of locust control agents."