|Scharf, Michael -|
Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 22, 2011
Publication Date: June 1, 2011
Citation: Tarver, M.R., Schmelz, E.A., Scharf, M.E. 2011. Soldier caste influences on candidate primer pheromone levels and juvenile hormone-dependent caste differentiation in workers of the termite Reticulitermes flavipes. Journal of Insect Physiology. 57:771–777. Interpretive Summary: Caste systems are common underlying features of all social insects. Termites use multiple castes within a colony to be efficient, each performing specific jobs. How termite castes are formed, relies on multiple internal and external factors, such as nestmate chemical communication. Thus, chemical signaling in social insect colonies is important for maintaining caste cohesive and efficient social structure. This work focuses on the influence of the soldier termite on nestmate worker termites. Our findings provide evidence that the two main soldier chemicals have a direct impact on nestmate worker termites. Where one chemical, '-cadinene, has a stimulatory effect on caste differentiation, while the second, '-cadinenal, has a potential inhibitory effect. Together these findings provide novel evidence that soldiers influence worker caste differentiation through chemical communication. These finding also could play a major role in the identification of novel termiticides, capable of disrupting the termite’s natural caste differentiation process.
Technical Abstract: Caste systems and the division of labor they make possible are common underlying features of all social insects. Multiple extrinsic factors have been shown to impact caste differentiation; for example, primer pheromones are chemical signaling molecules produced by certain castes that impact developmental physiology of nestmates. Thus, chemical signaling in social insect colonies is integral for maintaining caste homeostasis and a cohesive, efficient social structure. We examined the influences of terminally developed soldier termites on (1) candidate primer pheromone levels and (2) caste differentiation in developmentally totipotent workers. Our findings provide evidence that the two main soldier terpenes, '-cadinene (CAD) and '-cadinenal (ALD), accumulate in nestmate workers only in the presence of soldiers, that soldiers can modulate developmental-hormone response thresholds of workers via CAD and ALD action, and that CAD and ALD (respectively) are caste stimulatory and inhibitory components of chemical blends present in soldier heads. Together these findings provided novel evidence that soldiers influence worker caste differentiation by either transferring terpene primer pheromonal compounds to workers, or by influencing de novo biosynthesis of these compounds in workers themselves.