Identification of a worker arrestant aggregation pheromone in the Formosan subterranean termite Coptotermes formosanus

Abstract

Pheromones play a pivotal role in coordinating collective activities. Recent research has demonstrated that workers of the Japanese subterranean termite, Reticulitermes speratus, secrete an aggregation pheromone that induces prolonged aggregation of nestmate workers, facilitating efficient dead-wood digestion and colony expansion. The question remains: do other termite species also utilize aggregation pheromones? In this study, we establish that workers of the Formosan subterranean termite, Coptotermes formosanus, also use an aggregation pheromone for sustained aggregation. Through bioassays and gas-chromatography mass-spectrometry (GC-MS) analysis, we determined that the pheromone possesses arrestant activity but no attractant activity. The primary constituents are four fatty acids: palmitoleic acid, palmitic acid, (Z)-10-heptadecenoic acid, and stearic acid. The inclusion of cholesterol and cuticular hydrocarbons reinforces its arrestant activity. Further, GC-MS examination of wood and soil extracts, which serve as termite food, indicated that nearly all of the aggregation pheromone components likely originate from the workers or their gut symbionts rather than their diet. These findings imply that the arrestant activity of the C. formosanus aggregation pheromone surpasses that of R. speratus and that the unique presence of odd-numbered fatty acids combined with conspecific CHCs ensures the species-specific nature of the aggregation pheromone components. This research sheds light on the pheromonal communication mechanisms driving aggregation behavior in termites.