Name: a step-by-step guide to mosquito electroantennography
Uploaded: 2021-03-10T14:30:00
Description: Watch this Scientific Journal Video about A Step-by-Step Guide to Mosquito Electroantennography at JoVE.com

I am grateful to Dr. Cl&#233;ment Vinauger and Dr. Jeffrey Riffell for helpful discussions. The following reagents were obtained through BEI Resources, NIAID, NIH: Anopheles stephensi, Strain STE2, MRA-128, contributed by Mark Q. Benedict; Aedes aegypti, Strain ROCK, MRA-734, contributed by David W. Severson; Culex quinquefasciatus, Strain JHB, Eggs, NR-43025. The author thanks Dr. Jake Tu, Dr. Nisha Duggal, Dr. James Weger and Jeffrey Marano for providing Culex quinquefasciatus and Anopheles stephensi (strain: Liston) mosquito eggs. Aedes albopictus and Toxorhynchites rutilus septentrionalis are derived from field mosquitoes collected by the author in the New River Valley area (VA, USA). This work was supported by The Department of Biochemistry and The Fralin Life Science Institute.

1. Saline solution preparation
<ol>
	<li>Prepare the saline in advance and store in the fridge.</li>
	<li>Follow Beyenbach and Masia26 to prepare the solution. 
	&#8203;NOTE: Saline recipe in mM: 150.0 NaCl, 25.0 HEPES, 5.0 glucose, 3.4 KCl, 1.8 NaHCO3, 1.7 CaCl2, and 1.0 MgCl2. The pH is adjusted to 7.1 with 1 M NaOH. Do not add glucose or sucrose to the preparation at this time to increase shelf storage. Add the needed quantity to the saline right before r...

<ol>
	<li>World Health Organization. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=World+health+statistics+2019:+monitoring+health+for+the+SDGs,+sustainable+development+goals.">World health statistics 2019: monitoring health for the SDGs, sustainable development goals.</a> World Health Organization. , (2019).</li><li>Takken, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+olfaction+in+host-seeking+of+mosquitoes:+a+review.">The role of olfaction in host-seeking of mosquitoes: a review.</a> International Journal of Tropical Insect Science. 12 (1-2-3), 287-295 (1991).</li><li>Zwiebel, L. J., Takken, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Olfactory+regulation+of+mosquito-host+interactions.">Olfactory regulation of mosquito-host interactions.</a> Insect Biochemistry and Molecular Biology. 34 (7), 645-652 (2004).</li><li>Potter, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stop+the+biting:+targeting+a+mosquito's+sense+of+smell.">Stop the biting: targeting a mosquito's sense of smell.</a> Cell. 156 (5), 878-881 (2014).</li><li>Paluch, G., Bartholomay, L., Coats, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mosquito+repellents:+a+review+of+chemical+structure+diversity+and+olfaction.">Mosquito repellents: a review of chemical structure diversity and olfaction.</a> Pest Management Science. 66 (9), 925-935 (2010).</li><li>Schneider, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrophysiological+investigation+on+the+antennal+receptors+of+the+silk+moth+during+chemical+and+mechanical+stimulation.">Electrophysiological investigation on the antennal receptors of the silk moth during chemical and mechanical stimulation.</a> Experientia. 13 (2), 89-91 (1957).</li><li>Raguso, R. 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H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroantennogram+responses+related+to+olfactory+conditioning+in+the+honeybee+(Apis+mellifera+ligustica).">Electroantennogram responses related to olfactory conditioning in the honeybee (Apis mellifera ligustica).</a> Journal of Insect Physiology. 37 (4), 319-324 (1991).</li><li>Patte, F., Etcheto, M., Marfaing, P., Laffort, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroantennogram+stimulus-response+curves+for+59+odourants+in+the+honeybee,+Apis+mellifica.">Electroantennogram stimulus-response curves for 59 odourants in the honeybee, Apis mellifica.</a> Journal of Insect Physiology. 35 (9), 667-675 (1989).</li><li>Alcorta, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+the+electroantennogram+in+Drosophila+melanogaster+and+its+use+for+identifying+olfactory+capture+and+transduction+mutants.">Characterization of the electroantennogram in Drosophila melanogaster and its use for identifying olfactory capture and transduction mutants.</a> Journal of Neurophysiology. 65 (3), 702-714 (1991).</li><li>Park, K. C., Ochieng, S. A., Zhu, J., Baker, T. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Odor+discrimination+using+insect+electroantennogram+responses+from+an+insect+antennal+array.">Odor discrimination using insect electroantennogram responses from an insect antennal array.</a> Chemical Senses. 27 (4), 343-352 (2002).</li><li>Du, Y. J., Millar, J. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroantennogram+and+oviposition+bioassay+responses+of+Culex+quinquefasciatus+and+Culex+tarsalis+(Diptera:+Culicidae)+to+chemicals+in+odors+from+Bermuda+grass+infusions.">Electroantennogram and oviposition bioassay responses of Culex quinquefasciatus and Culex tarsalis (Diptera: Culicidae) to chemicals in odors from Bermuda grass infusions.</a> Journal of Medical Entomology. 36 (2), 158-166 (1999).</li><li>Costantini, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroantennogram+and+behavioural+responses+of+the+malaria+vector+Anopheles+gambiae+to+human-specific+sweat+components.">Electroantennogram and behavioural responses of the malaria vector Anopheles gambiae to human-specific sweat components.</a> Medical and Veterinary Entomology. 15 (3), 259-266 (2001).</li><li>Collins, L. E., Blackwell, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroantennogram+studies+of+potential+oviposition+attractants+for+Toxorhynchites+moctezuma+and+T.+amboinensis+mosquitoes.">Electroantennogram studies of potential oviposition attractants for Toxorhynchites moctezuma and T. amboinensis mosquitoes.</a> Physiological Entomology. 23 (3), 214-219 (1998).</li><li>Seenivasagan, T., Sharma, K. R., Sekhar, K., Ganesan, K., Prakash, S., Vijayaraghavan, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroantennogram,+flight+orientation,+and+oviposition+responses+of+Aedes+aegypti+to+the+oviposition+pheromone+n-heneicosane.">Electroantennogram, flight orientation, and oviposition responses of Aedes aegypti to the oviposition pheromone n-heneicosane.</a> Parasitology Research. 104 (4), 827-833 (2009).</li><li>Puri, S. N., Mendki, M. J., Sukumaran, D., Ganesan, K., Prakash, S., Sekhar, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroantennogram+and+behavioral+responses+of+Culex+quinquefasciatus+(Diptera:+Culicidae)+females+to+chemicals+found+in+human+skin+emanations.">Electroantennogram and behavioral responses of Culex quinquefasciatus (Diptera: Culicidae) females to chemicals found in human skin emanations.</a> Journal of Medical Entomology. 43 (2), 207-213 (2014).</li><li>Cooperband, M. F., McElfresh, J. S., Millar, J. G., Carde, R. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Attraction+of+female+Culex+quinquefasciatus+Say+(Diptera:+Culicidae)+to+odors+from+chicken+feces.">Attraction of female Culex quinquefasciatus Say (Diptera: Culicidae) to odors from chicken feces.</a> Journal of Insect Physiology. 54 (7), 1184-1192 (2008).</li><li>Dekker, T., Ignell, R., Ghebru, M., Glinwood, R., Hopkins, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+mosquito+repellent+odours+from+Ocimum+forskolei.">Identification of mosquito repellent odours from Ocimum forskolei.</a> Parasites &amp; Vectors. 4 (1), 183 (2011).</li><li>Choo, Y. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reverse+chemical+ecology+approach+for+the+identification+of+an+oviposition+attractant+for+Culex+quinquefasciatus.">Reverse chemical ecology approach for the identification of an oviposition attractant for Culex quinquefasciatus.</a> Proceedings of the National Academy of Sciences. 115 (4), 714-719 (2018).</li><li>Wolff, G. H., Lahond&#232;re, C., Vinauger, C., Riffell, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuromodulation+and+differential+learning+across+mosquito+species.">Neuromodulation and differential learning across mosquito species.</a> bioRxiv. , 755017 (2019).</li><li>Lahond&#232;re, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+olfactory+basis+of+orchid+pollination+by+mosquitoes.">The olfactory basis of orchid pollination by mosquitoes.</a> Proceedings of the National Academy of Sciences. 117 (1), 708-716 (2020).</li><li>Beyenbach, K., Masia, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane+conductances+of+principal+cells+in+Malpighian+tubules+of+Aedes+aegypti.">Membrane conductances of principal cells in Malpighian tubules of Aedes aegypti.</a> Journal of Insect Physiology. 48, 375-386 (2002).</li><li>Oesterle, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> The Pipette Cookbook. , (2018).</li><li>R Core Team. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=R:+A+language+and+environment+for+statistical+computing.">R: A language and environment for statistical computing.</a> R Foundation for Statistical Computing. , (2018).</li><li>Afify, A., Betz, J. F., Riabinina, O., Lahond&#232;re, C., Potter, C. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Commonly+used+insect+repellents+hide+human+odors+from+Anopheles+mosquitoes.">Commonly used insect repellents hide human odors from Anopheles mosquitoes.</a> Current Biology. 29 (21), 3669-3680 (2019).</li><li>Martin, F., Riveron, J., Alcorta, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Environmental+temperature+modulates+olfactory+reception+in+Drosophila+melanogaster.">Environmental temperature modulates olfactory reception in Drosophila melanogaster.</a> Journal of Insect Physiology. 57 (12), 1631-1642 (2011).</li><li>Qiu, Y. T., Gort, G., Torricelli, R., Takken, W., van Loon, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effects+of+blood-feeding+on+olfactory+sensitivity+of+the+malaria+mosquito+Anopheles+gambiae:+application+of+mixed+linear+models+to+account+for+repeated+measurements.">Effects of blood-feeding on olfactory sensitivity of the malaria mosquito Anopheles gambiae: application of mixed linear models to account for repeated measurements.</a> Journal of Insect Physiology. 59 (11), 1111-1118 (2013).</li><li>Taylor, B., Jones, M. D. 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Olfactory mediated behaviors are affected by many factors, including physiological (e.g., age, time of day) and environmental (e.g., temperature, relative humidity)30. Thus, when conducting EAGs, it is essential to use insects that are in the same physiological status (i.e., monitoring for age, starving, mating)31 and to also maintain a warm and humid environment around the preparation to avoid desiccation. A temperature around 25 &#176;C is ideal and 60% to 80% humidity fo...

Mosquitoes are the deadliest organisms on earth, claiming the lives of more than one million people per year and place more than half the world population at risk of exposure to the pathogens they transmit, while biting1. These insects rely on a wide range of cues (i.e., thermal, visual, mechanical, olfactory, auditory) to locate a host to feed on (both plant and animal), for mating and oviposition, as well as to avoid predators at both the larval and adult stages2,3. Among these senses, olfaction plays a critical role in the above mentioned behaviors, in particular for medium to long-range detection of odorant molecules2,3. Odors emitted by a host or an oviposition site are detected by various specific olfactory receptors (e.g., GRs, ORs, IRs) located on the mosquito palps proboscis, tarsi, and antennae2,3.
As olfaction is a key component of their host-seeking (plant and animal), mating and oviposition behaviors, it thus constitutes an ideal target to study to develop new tools for mosquito control4. Research on repellents (e.g., DEET, IR3535, picaridin) and baits (e.g., BG sentinel human lure) is extremely prolific5, but because of the current challenges in mosquito control (e.g., insecticide resistance, invasive species), it is essential to develop new efficient control methods informed by the mosquito biology.
Many techniques (e.g., olfactometer, landing assays, electrophysiology) have been used to assess the bioactivity of compounds or mixtures of compounds in mosquitoes. Among them, electroantennography (or electroantennograms (EAGs)) can be used to determine whether the odorants are detected by the mosquito antennae. This technique was initially developed by Schneider6 and has been used in many different insect genera since then, including moths7,8,9, bumblebees10,11, honeybees12,13, and fruit flies14,15 to name a few. Electroantennography has also been employed using various protocols, including single or multiple antennae in mosquitoes16,17,18,19,20,21,22,23,24,25.
Mosquitoes are relatively small and delicate insects with rather thin antennae. While performing EAGs on larger insects such as moths or bumblebees is relatively easy because of their larger size and thicker antennae, conducting EAGs in mosquitoes can be challenging. In particular, maintaining a good signal-to-noise ratio and a lasting responsive preparation are two major requirements for data reproducibility and reliability.
The step-by-step guide to low noise EAGs proposed here directly offers solutions to these limitations and make this protocol applicable to several mosquito species from various genera, including Aedes, Anopheles, Culex, and Toxorhynchites, and describes the technique for both females and males. Electroantennography offers a quick yet reliable way to screen and determine bioactive compounds that can then be leveraged in bait development after valence has been determined with behavioral assays.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Air table Clean Bench</td>
			<td>TMC</td>
			<td>https://www.techmfg.com/products/labtables/cleanbench63series/accessoriess</td>
			<td>Noise reducer</td>
		</tr>
		<tr>
			<td>Analog-to-digital board</td>
			<td>National Instruments</td>
			<td>BNC-2090A</td>
			<td></td>
		</tr>
		<tr>
			<td>Benchtop Flowbuddy Complete</td>
			<td>Genesee Scientific</td>
			<td>59-122BC</td>
			<td>To anesthesize mosquitoes</td>
		</tr>
		<tr>
			<td>Borosillicate glass capillary</td>
			<td>Sutter Instrument</td>
			<td>B100-78-10</td>
			<td>To make the recording and references capillaries</td>
		</tr>
		<tr>
			<td>Chemicals</td>
			<td>Sigma Aldrich</td>
			<td>Benzaldehyde: 418099-100 mL; Butyric acid: B103500-100mL; 1-Hexanol: 471402-100mL; Mineral oil: M8410-1L</td>
			<td>Chemicals used for the experiments presented here</td>
		</tr>
		<tr>
			<td>CO2</td>
			<td>Airgas or Praxair</td>
			<td>N/A</td>
			<td>To anesthesize mosquitoes</td>
		</tr>
		<tr>
			<td>Cold Light Source</td>
			<td>Volpi</td>
			<td>NCL-150</td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable syringes</td>
			<td>BD</td>
			<td>1 mL (309628)&#160; / 3 mL (309657)</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrode cables</td>
			<td>World Precision Instruments</td>
			<td>5371</td>
			<td></td>
		</tr>
		<tr>
			<td>Electrode gel salt free</td>
			<td>Parkerlabs</td>
			<td>12-08-Spectra-360</td>
			<td></td>
		</tr>
		<tr>
			<td>Faraday cage</td>
			<td>TMC</td>
			<td>https://www.techmfg.com/products/electric-and-magnetic-field-cancellation/faradaycages</td>
			<td>Noise reducer</td>
		</tr>
		<tr>
			<td>Flowmeters</td>
			<td>Bel-art</td>
			<td>65 mm (H40406-0010) / 150 mm (H40407-0075)</td>
			<td>One of each</td>
		</tr>
		<tr>
			<td>GCMS vials and caps</td>
			<td>Thermo-fisher scientific</td>
			<td>2-SVWKA8-CPK</td>
			<td>To prepare odorant dilutions</td>
		</tr>
		<tr>
			<td>Glass syringes (Fortuna)</td>
			<td>Sigma Aldrich</td>
			<td>Z314307</td>
			<td>For odor delivery to the EAG prep</td>
		</tr>
		<tr>
			<td>Humbug</td>
			<td>Quest Scientific</td>
			<td>http://www.quest-sci.com/</td>
			<td>Noise reducer</td>
		</tr>
		<tr>
			<td>2 mm Jack Holder, Narrow, 90 deg., With Wire</td>
			<td>A-M Systems</td>
			<td>675748</td>
			<td>Electrode holder</td>
		</tr>
		<tr>
			<td>Magnetic bases</td>
			<td>Kanetec</td>
			<td>MB-FX</td>
			<td>x 2</td>
		</tr>
		<tr>
			<td>MATLAB + Toolboxes</td>
			<td>Mathworks</td>
			<td>https://www.mathworks.com/products/matlab.html</td>
			<td>For delivering the pulses</td>
		</tr>
		<tr>
			<td>Medical air</td>
			<td>Airgas or Praxair</td>
			<td>N/A</td>
			<td>For main airline</td>
		</tr>
		<tr>
			<td>Microscope</td>
			<td>Nikkon</td>
			<td>SMZ-800N</td>
			<td></td>
		</tr>
		<tr>
			<td>Micromanipulators Three-Axis Coarse/Fine Compact Micromanipulator</td>
			<td>Narishige</td>
			<td>MHW-3</td>
			<td>x 2</td>
		</tr>
		<tr>
			<td>Microelectrode amplifier with headstage</td>
			<td>A-M Systems</td>
			<td>Model 1800</td>
			<td></td>
		</tr>
		<tr>
			<td>Mosquito rearing supplies</td>
			<td>Bioquip</td>
			<td>https://www.bioquip.com/Search/WebCatalog.asp</td>
			<td></td>
		</tr>
		<tr>
			<td>Needles</td>
			<td>BD</td>
			<td>25G (305127) / 21G (305165)</td>
			<td></td>
		</tr>
		<tr>
			<td>Pasteur pipettes</td>
			<td>Fisher Scientific</td>
			<td>13-678-6A</td>
			<td>For odor delivery to the EAG prep</td>
		</tr>
		<tr>
			<td>PTFE Tubing of different diameters</td>
			<td>Mc Master Carr</td>
			<td>N/A</td>
			<td>To connect solenoid valve, flowmeter, airline ect.</td>
		</tr>
		<tr>
			<td>30V/5A DC Power Supply</td>
			<td>Dr. Meter</td>
			<td>PS-305DM</td>
			<td></td>
		</tr>
		<tr>
			<td>R version 3.5.1</td>
			<td>R project</td>
			<td>https://www.r-project.org/</td>
			<td>For data analyses</td>
		</tr>
		<tr>
			<td>Relay for solenoid valve</td>
			<td>N/A</td>
			<td>Custom made</td>
			<td></td>
		</tr>
		<tr>
			<td>Silver wire 0.01&#8221;</td>
			<td>A-M Systems</td>
			<td>782500</td>
			<td></td>
		</tr>
		<tr>
			<td>Solenoid valve (3-way)</td>
			<td>The Lee Company</td>
			<td>LHDA0533115H</td>
			<td></td>
		</tr>
		<tr>
			<td>WinEDR software</td>
			<td>Strathclyde Electrophysiology Software</td>
			<td>WinEDR V3.9.1</td>
			<td>For EAG recording</td>
		</tr>
		<tr>
			<td>Whatman paper</td>
			<td>Cole Parmer</td>
			<td>UX-06648-03</td>
			<td>To load chemical in glass syringe / Pasteur pipette</td>
		</tr>
	</tbody>
</table>

a step-by-step guide to mosquito electroantennography

Female mosquitoes are the deadliest animals on earth, claiming the lives of more than 1 million people every year due to pathogens they transmit when acquiring a blood-meal. To locate a host to feed on, mosquitoes rely on a wide range of sensory cues, including visual, mechanical, thermal, and olfactory. The study details a technique, electroantennography (EAG), that allows researchers to assess whether the mosquitoes can detect individual chemicals and blends of chemicals in a concentration-dependent manner. When coupled with gas-chromatography (GC-EAG), this technique allows to expose the antennae to a full headspace/complex mixture and determines which chemicals present in the sample of interest, the mosquito can detect. This is applicable to host body odors as well as plant floral bouquets or other ecologically relevant odors (e.g., oviposition sites odorants). Here, we described a protocol that permits long durations of preparation responsiveness time and is applicable to both female and male mosquitoes from multiple genera, including Aedes, Culex, Anopheles, and Toxorhynchites mosquitoes. As olfaction plays a major part in mosquito-host interactions and mosquito biology in general, EAGs and GC-EAG can reveal compounds of interest for the development of new disease vector control strategies (e.g., baits). Complemented with behavioral assays, the valence (e.g., attractant, repellent) of each chemical can be determined.

Electroantennography is a powerful tool to determine whether a chemical or blend of chemicals is detected by an insect antenna. It can also be used to determine the detection threshold for a given chemical using a gradual increase of concentration (i.e., dose curve response, Figure 4B). Moreover, it is useful to test the effects of repellent on the response to host-related odors29.
Positive and negative controls should always be used in EAG...

Watch this Scientific Journal Video about A Step-by-Step Guide to Mosquito Electroantennography at JoVE.com

A Step-by-Step Guide to Mosquito Electroantennography

The present article details a step-by-step protocol for successful and low noise electroantennograms in several genera of mosquitoes, including both females and males.

Female mosquitoes are the deadliest animals on earth, claiming the lives of more than 1 million people every year due to pathogens they transmit when ...

For electroantennography, using mosquitoes in a specific and consistent physiological status is critical to obtain reliable results. The step-by-step protocol allows for lasting electroantennographic recordings in mosquitoes. The method can be used in several mosquito species, and in both males and females.The electroantennographic technique can also be transposed to other insect models, including beetles, flies, kissing bugs, and ants. To begin, remove the 1.5 milliliter amber vials containing the odorant mixtures and a solvent control from the 20 degree Celsius freezer in which they're stored to prevent degradation. Next, pipette out 10 microliters of the odorant solution onto a piece of filter paper loaded inside a labeled glass syringe.Isolate the mosquitoes on the day of the experiment. Working under the microscope, gently break the tip of two borosilicate capillaries with filaments using a pair of forceps. Before running the electroantennography, or EAG experiment, ensure that the electrode holders are clear inside, with no borosilicate debris.Then perform chloridization by soaking the silver wires of the electrode holders in pure bleach for five minutes, until the wires turn dark, matte gray. Then rinse the wires. Loosen the rubber stopper and use a 20 gauge needle to fill the inside of the capillary with saline solution.Rinse the capillaries and insert the wires in the two capillaries. Keep the tip of the wire less than one millimeter from the tip of the capillary. Pass the capillary through the rubber ring inside the electrode holder without breaking it and gently tighten the rubber stopper, after verifying that no air bubbles are present.Use the capillary with the wider opening on the reference electrode holder and the smaller opening on the recording electrode holder. Leave the two mounted electrode holders on a wet cleaning wipe to prevent the tip from drying out until ready to mount the head. Ensure that the air table is up.There is no blockage in the airline and the air is on. Verify that the tank of medical air is full to avoid changing it in the middle of the experiment and confirm bubbles in the humidifier. Turn on the computers, the software applications, and the valve power supply.After verifying the internet connection, deliver a control pulse to verify that the valve delivering the pulses is functional. Place an aluminum plate on ice with a piece of wet cleaning wipe over it and put a small dollop of electrode gel in a corner. Place a mosquito cup on ice to let the mosquito cool down.Clip the tip of each antenna of the mosquito with micro scissors. Use forceps to drag the mosquito next to the electrode gel dollop and dip each antenna's tip gently in the gel. Using forceps, pull the mosquito antennae out, while maintaining them next to each other.Chop the head of the mosquito using micro scissors. Gently dip the tip of the reference electrode in the gel and place it in contact with the neck, letting the head stick to it. Place the reference head electrode on a micro manipulator.Connect both electrode holders to the amplifier. Use the micro manipulator to place the recording electrode as close as possible to the antenna tips. Then insert the antenna tips in the recording electrode.Place the airline tubing close to the mosquito head preparation, at one centimeter. Turn on the amplifier and the noise reducer and ensure that the baseline signal is not noisy. Once the noise level is satisfactory, insert the first odor syringe in the airline hole to perform the test and close the Faraday cage.Then click record on the EAG software to deliver the pulse. Measure EAG responses as amplitude in millivolts and then proceed with the next odor or concentration. The experiment successfully demonstrates that mosquito species can exhibit variable olfactory responses to different chemicals.There was an absence of response to the mineral oil, which was used as a negative control. Error in the results due to electrical noise can be reduced by grounding the elements to the Faraday cage, using alligator clips. The response threshold to the same odorant can vary in magnitude for different species of mosquitoes.For example, Toxorhynchites rutilus septentrionalis mosquitoes produce very large EAGs, compared to Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. A large deflection in response to the positive control, benzaldehyde, was noticed. While there was a lack of response to the negative control, mineral oil.These average antennal responses are shown in a bar diagram. Additionally, the threshold of detecting a specific chemical for each mosquito species was determined by presenting the antenna, the increasing concentrations of the chemical, and plotting a dose response curve. It is important to start the recording as soon as possible after the head has been chopped and mounted, to ensure great responsiveness of the preparation.EAG allows to determine whether the mosquito antennae respond to a given chemical at a given concentration. However, it does not allow for determining the balance of this chemical. For example, whether it's an attractant or repentance.

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