Queen pheromone promotes production of salivary lysozyme by workers in a termite

Abstract

Social insects have highly elaborated communication systems. In particular, communication via pheromones is important for maintaining complex social roles and behaviors. Brood care is a typical activity that involves pheromonal communication among colony members. In termites, eggs cannot survive without grooming by workers. The workers coat the eggs with their saliva, which contains an antibacterial protein lysozyme that protects the eggs against bacterial pathogens. The more eggs a colony has, the more salivary lysozyme the workers need to produce for egg grooming. However, it is unknown how termite workers regulate their lysozyme production. Here we show that the queen pheromone, which is emitted by both queens and eggs, promotes lysozyme production by workers in the termite Reticulitermes speratus. Exposure to artificial queen pheromone significantly increased the production of salivary lysozyme by workers as well as the artificial addition of eggs. Furthermore, our survey of field colonies revealed clear seasonality in the production of salivary lysozyme. The seasonal pattern of lysozyme production matched well with the seasonal change of the number of eggs per colony. In addition to the known function of the queen pheromone as an inhibitor of neotenic queen differentiation, this study reveals that the same pheromone also acts as a promoter of lysozyme production in workers. We describe a novel function of the multifunctional queen pheromone in termites and provide new insights into the evolutionary parsimony of social insect pheromones.