Odor aversion and pathogen-removal efficiency in grooming behavior of the termite Coptotermes formosanus.

Abstract

The results of biocontrol with entomopathogens in termites have been discouraging because of the strong social hygiene behavior for removing pathogens from termite colonies. However, the mechanism of pathogen detection is still unclear. For the successful application of biopesticides to termites in nature, it would be beneficial to identify substances that could disrupt the termite's ability to perceive pathogens. We hypothesized that termites can perceive pathogens and this ability plays an important role in effective hygiene behavior. In this study, pathogen-detection in the subterranean termite Coptotermes formosanus was investigated. We performed quantitative assays on conidia removal by grooming behavior using epifluoresence microscopy and Y-maze tests to examine the perception of fungal odor by termites. Three species each of high- and low-virulence entomopathogenic fungi were used in each test. The results demonstrated that termites removed conidia more effectively from a nestmate's cuticle if its odor elicited stronger aversion. Highly virulent pathogens showed higher attachment rates to termite surfaces and their odors were more strongly avoided than those of low-virulence isolates in the same species. Moreover, termites appeared to groom each other more persistently when they had more conidia on their bodies. In brief, insect perception of pathogen-related odor seems to play a role in the mechanism of their hygiene behavior.