Trail Communication Regulated by Two Trail Pheromone Components in the Fungus-Growing Termite Odontotermes formosanus (Shiraki)

Abstract

The eusocial termites are well accomplished in chemical communication, but how they achieve the communication using trace amount of no more than two pheromone components is mostly unknown. In this study, the foraging process and trail pheromones of the fungus-growing termite Odontotermes formosanus (Shiraki) were systematically studied and monitored in real-time using a combination of techniques, including video analysis, solid-phase microextraction, gas chromatography coupled with either mass spectrometry or an electroantennographic detector, and bioassays. The trail pheromone components in foraging workers were (3Z)-dodec-3-en-1-ol and (3Z,6Z)-dodeca-3,6-dien-1-ol secreted by their sternal glands. Interestingly, ratio of the two components changed according to the behaviors that the termites were displaying. This situation only occurs in termites whereas ratios of pheromone components are fixed and species-specific for other insect cuticular glands. Moreover, in bioassays, the active thresholds of the two components ranged from 1 fg/cm to 10 pg/cm according to the behavioral contexts or the pheromonal exposure of tested workers. The two components did not act in synergy. (3Z)-Dodec-3-en-1-ol induced orientation behavior of termites that explore their environment, whereas (3Z,6Z)-dodeca-3,6-dien-1-ol had both an orientation effect and a recruitment effect when food was discovered. The trail pheromone of O. formosanus was regulated both quantitatively by the increasing number of workers involved in the early phases of foraging process, and qualitatively by the change in ratio of the two pheromone components on sternal glandular cuticle in the food-collecting workers. In bioassays, the responses of workers to the pheromone were also affected by the variation in pheromone concentration and component ratio in the microenvironment. Thus, this termite could exchange more information with nestmates using the traces of the two trail pheromone components that can be easily regulated within a limited microenvironment formed by the tunnels or chambers.

Breaking the cipher: ant eavesdropping on the variational trail pheromone of its termite prey

“…The complexity of the pheromonal use in termites is evidenced by the change in signal interpretation with changing DDE and DOE ratios. Beyond the data that we provide in this study, the complexity of termite trail pheromones is supported by Wen et al [29], which showed similar patterns for O. formosanus (Macrotermitinae).…”

“…Foraging in termites, and in most ants, is a collective task during which the risk of predation is high. Communication strategies may therefore be used to ensure the efficient gathering of food, such as foraging communication, including the secretion of a trail-following pheromone [27][28][29][30], alarm communication with vibrations or alarm pheromones [31], and nest-mate recognition to avoid mistakes in defensive behaviour [32,33]. To be successful, foraging communication should transmit all the basic information related to the food source, such as quantity, quality, direction and location.…”

“…In Odontotermes formosanus (Macrotermitinae), trail orientation is induced by (3Z)-dodec-3-en-1-ol (DOE) whereas (3Z,6Z)-dodeca-3,6-dien-1-ol (DDE) has both an orientation effect and a recruitment effect when food is discovered [29]. Macrotermitinae species are known to have high population densities and may therefore provide an abundant source of food for predators, with ant species being the most important ones.…”

Poison and alarm: The Asian hornetVespa velutinauses sting venom volatiles as alarm pheromone

“…Pheromones are important information agents and help to regulate colony behaviour in social insects, such as honey bees (Slessor et al, 2005), ants (Hölldobler, 1995), termites (Wen et al, 2014) and wasps Turillazzi and Bruschini, 2010). Alarm pheromones can play dual roles, by activating nest defence and serving as a warning that allows foragers to avoid dangerous sites.…”

“…In most social insects studied to date, alarm pheromones consist of multi-component blends Turillazzi and Bruschini, 2010;Hölldobler, 1995;Slessor et al, 2005;Wen et al, 2014). Hornet alarm pheromones also contain multiple components, some of which are known to elicit alarm behaviour.…”