Above- and belowground olfactometers for high throughput bioassays

T. Turlings¹, A. Davison², I. Ricard², C. Tamo¹, S. Rasmann¹ and M. Held¹

¹Institute of Zoology, University of Neuchâtel, Neuchâtel, Switzerland
²EPF-Lausanne, Mathematics/Statistics, Lausanne, Switzerland

Customary procedures to determine attraction to odor sources and to identify the substances that are responsible for the attraction require tedious and time-consuming bioassays, as well as separate experiments using specialized methods for the collection, analyses, and identification of the chemicals. The inclusion of several different odor sources and treatments in such studies can make them exceedingly lengthy and impossible to accomplish within a reasonable time period. We have developed two types of six-arm olfactometers to facilitate our research on the chemical signals emitted by insect-damaged plants that serve to attract parasitic wasps and entomopathogenic nematodes, which are natural enemies of the damaging insects. One olfactometer is used to study aboveground and another to study belowground attraction. Using log-linear models for the statistical treatment of the data allows for the testing of multiple individuals at the same time and the models control for overdispersion and positional effects. In addition to allowing us to test the relative attractiveness of up to six odor sources at the same time, the equipment is also designed to simultaneously sample part of the volatiles emitted by the odor sources, which can subsequently be identified and quantified. The 6-arm olfactometers offer several advantages over conventional olfactometer designs and have proven to be highly effective in aiding us to identify key attractants involved in tritrophic interactions. The above- and belowground olfactometers can be attached to each other and we currently use this feature to investigate how aboveground herbivory affects belowground interactions and visa versa.

Paper presented at Measuring Behavior 2005 , 5^th International Conference on Methods and Techniques in Behavioral Research, 30 August - 2 September 2005, Wageningen, The Netherlands.

© 2005 Noldus Information Technology bv