SELECTIVE ODOR PERCEPTION IN THE SOIL COLLEMBOLA ONYCHIURUS-ARMATUS

The olfactorial response of the fungivorous soil collembolan Onychiurus armatus was examined in a bioassay covering volatile compounds identified in the odor blends of two of its preferred fungal species Mortierella isabellina and Verticillium bulbillosum. The odor of the fungi was trapped using activated carbon filters, extracted with diethyl ether, and subjected to GC-MS analysis. About 50% of the compounds resolved by GC were identified by a combination of electron impact and chemical ionization mass spectrometry. In a Y-shaped olfactometer the collembolans were attracted to a variety of common odors, such as CO2 and 2-methyl-1-propanol, and a species-specific odor, such as 1-heptene, and arrested by, for example, decanal and 2-octene. The response was not improved by pairwise combinations of common and specific odors. An amount of 0.5 ng of ethyl acetate or 3 pg of 1-pentanol was sufficient to attract the collembolans. The specific compounds of V. bulbillosum, 1-heptene and 1-octen-3-ol, may be key stimuli explaining why O. armatus prefers V. bulbillosum.