Division of labour in eusocial insects is characterised by efficient communication systems based on pheromones. Among such insects, termites have evolved specialised sterile defenders, called soldiers. Because they are incapable of feeding themselves, it has been suggested that soldiers are sustained by workers and emit the pheromone arresting workers. However, such a soldier pheromone has not been identified in any termite species, and the details of the soldier-worker interaction remain to be explored. In the present study, the authors identified a soldier-specific volatile sesquiterpene as a worker arrestant, which also acts as a primer pheromone regulating soldier differentiation and fungistatic agent in a termite Reticulitermes speratus. Chemical analyses revealed that (-)-?-elemene is the major component of soldier extract, and its authentic standard exhibited arrestant activity to workers and inhibited the differentiation from workers to soldiers. This compound also showed fungistatic activity against entomopathogenic fungi. These suggest that (-)-?-elemene secreted by soldiers acts not only as a worker arrestant but also as one component of inhibitory primer pheromone and an anti-pathogenic agent. The authors concluded that the study provides novel evidence supporting the multi-functionality of termite soldier pheromone and provides new insights into the role of soldiers and the evolutionary mechanisms of pheromone compounds.
Authors: Mitaka Y, Mori N, Matsuura K. ; Full Source: Proceedings in Biological Science. 2017 Jul 26;284(1859). pii: 20171134. doi: 10.1098/rspb.2017.1134.