Olfactory Cues from Pathogenic Fungus Affect the Direction of Motion of Termites, Coptotermes formosanus.

Abstract

Formosan subterranean termites, Coptotermes formosanus, tend to avoid pathogen odors when tested in Y-tube olfactometers, but approach and groom exposed nestmates to remove pathogens from their cuticle and maintain a healthy population. To better understand their differential reaction to pathogens and their odors, the relationship between odor cues and direction of motion was examined with the fungus Isaria fumosorosea K3 strain. The results indicate that nestmate odor was strongly attractive only in tests where fungal odors were present in both branches of the olfactometer. Termites generally avoid fungal odors when offered a choice without fungal odor. We also tested termite aversion to 3-octanone and 1-octen-3-ol, major surface chemical compounds of I. fumosorosea K3, and estimated the total mass of these compounds present on the conidial surface by direct extraction method. The total quantity of these chemicals on the surface of fungal conidia was estimated to be approximately 0.01 ng per 10(7) conidia. This study demonstrates a context dependent behavioral change in termites in response to the odors of pathogenic fungi.