Induction heating coil heating improves the efficiency of insect olfactory studies

Authors: YANG, LIU - University Of Florida; LIU, YUZHE - Auburn University; RICHOUX, GARY - University Of Florida; Bernier, Ulrich; Linthicum, Kenneth - Ken; BLOOMQUIST, JEFFREY - University Of Florida

Submitted to: Frontiers in Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2019
Publication Date: 6/28/2019
Citation: Yang, L., Liu, Y., Richoux, G.M., Bernier, U.R., Linthicum, K., Bloomquist, J.R. 2019. Induction heating coil heating improves the efficiency of insect olfactory studies. Frontiers in Ecology and Evolution. 7:247. https://doi.org/10.3389/fevo.2019.00247.
DOI: https://doi.org/10.3389/fevo.2019.00247

Interpretive Summary: Electroantennography (EAG) is a technique to measure the sensation of smell in insect antennas. Although large EAG responses can be obtained from compounds such as insect pheromones, difficulties caused by low dose or low volatility cause difficulties with some behaviorally relevant chemicals such as insect repellents due to small signals and noise background. To increase the sensitivity of the EAG we developed a system to heat chemical samples to vaporization by electromagnetic induction, which increases antennal responses over 10-fold and reduces significantly the amount of chemical used. This technique will improve the ability to test chemicals by reducing the amount of chemical needed for testing, especially with those chemicals with low volatility.

Technical Abstract: Electroantennography (EAG) is a commonly used method to study the olfactory responses of insects, but many behaviorally relevant odor responses are difficult to discern from noise because only a small amount of chemical is available. Here we built a coupled induction heating-electroantennogram (IH-EAG) system to improve the release efficiency of tested compounds. This system allows precise temperature control from room temperature to 600°C without changing the air delivery temperature to the antennae. After heating to 100°C, EAG response to 0.1 mg of DEET increased from 0.11 to 0.33 mV, not significantly different from the EAG response to 1 mg and 10 mg of DEET at room temperature (ca. 23°C). Likewise, 1-octen-3-ol showed at 0.1 mg after heating to100°C that was equal to 1 mg at room temperature. When tested with the low volatility compound VUAA-1, the EAG response increased from 0.16 to 9.52 mV after heating to 500°C when applied on aluminum foil, and aluminum foil showed a significantly greater EAG response when compared to glass fiber filter. This method has the potential to be a significant advance for reducing the amount of chemical used in an EAG assay and allows for convenient testing of slow acting, less volatile compounds for eliciting an olfactory response on insects or other animals.