Year of Publication

2015

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Agriculture, Food and Environment

Department

Entomology

First Advisor

Dr. Xuguo Zhou

Second Advisor

Dr. Kenneth F. Haynes

Abstract

Undertaking behavior is the disposal of dead individuals in social colonies to prevent potential pathogenic attack. This behavioral trait has convergently evolved in social insects (primarily termites, ants, and honeybee), and is considered an essential adaptation to social living. In honey bee and ants, workers recognize dead colony members through the postmortem change of chemical profile, and corpses are usually removed out of nest. However, in termites, little is known about the behavioral pattern, chemical cue or molecular basis. In the eastern subterranean termite, Reticulitermes flavipes, this study investigated undertaking behavior toward corpses of different origins and postmortem times. Corpses of a competitive species, R. virginicus, were buried onsite by R. flavipes workers with a large group of soldiers guarding the burial site; while dead conspecifics of R. flavipes were retrieved and cannibalized. In addition, postmortem time played an important role in corpse management. Early death cue, a blend of 3-octanone and 3-octanol, emitted from workers to attract colony members to consume their bodies; the two volatiles rapidly decreased while the corpse decomposed, and burial behavior was alternatively employed at a late postmortem stage. Gene expression profiles of R. flavipes workers were established during cannibalism of freshly dead nestmates, burial of decayed nestmates, and burial of dead competitors. The results showed that gene expression signatures were associated with the behavioral responses, and burial behavior involved more differentially expressed genes in metabolic pathways, indicating a higher energetic output in burial than cannibalism. Our findings suggest that undertaking responses in R. flavipes are associated with the type of risk posed by the dead: cannibalism allows nutrient recycling in the colony, but burial would be warranted toward increased risks of pathogen infection or territorial intrusion. The use of early death cues that promotes cannibalism is adaptive to subterranean termites that feed on nutritionally poor diet. This study advances our understanding of social behavior in insects, and provides fundamental knowledge that may lead to new pest control approaches against R. flavipes.

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