Using Single Sensillum Recording to Detect Olfactory Neuron Responses of Bed Bugs to Semiochemicals

Summary

Bed bugs rely on olfactory receptor neurons housed in their antennal olfactory sensilla to detect semiochemicals in the environment. Utilizing single sensillum recording, we demonstrate a method to evaluate bed bug response to semiochemicals and explore the coding process involved.

Abstract

The insect olfactory system plays an important role in detecting semiochemicals in the environment. In particular, the antennal sensilla which house single or multiple neurons inside, are considered to make the major contribution in responding to the chemical stimuli. By directly recording action potential in the olfactory sensillum after exposure to stimuli, single sensillum recording (SSR) technique provides a powerful approach for investigating the neural responses of insects to chemical stimuli. For the bed bug, which is a notorious human parasite, multiple types of olfactory sensillum have been characterized. In this study, we demonstrated neural responses of bed bug olfactory sensilla to two chemical stimuli and the dose-dependent responses to one of them using the SSR method. This approach enables researchers to conduct early screening for individual chemical stimuli on the bed bug olfactory sensilla, which would provide valuable information for the development of new bed bug attractants or repellents and benefits the bed bug control efforts.

Introduction

The common bed bug Cimex lectularius L (Hemiptera: Cimicidae), as a temporary ectoparasite, is an obligated blood-sucking insect, which means their survival, development, and reproduction require blood sources from hosts, including both humans and animals^1,2. Although virus transmission has rarely been reported due to C. lectularius, the biting nuisance generated by an infestation seriously affects hosts both physically and psychologically³. The introduction and widespread use of chemical insecticides, especially DDT, lowered the risk of infestations and by the end of the 1950s infestations were at such a low level that they wer....

Protocol

1. Preparation of Instruments, Stimuli Solutions, and Bed Bugs

1. Prepare a 50% KNO₂ solution (w/v) in a 20 ml bottle.
2. Sharpen two tungsten microelectrodes in KNO₂ solution at 5 V by repeatedly dipping the tungsten electrodes in and out of the solution.
   1. Roughly sharpen the tungsten wire by dipping about 10 mm of the tungsten wire in and out of the KNO₂ solution at the speed of 2 dips/sec for about 5 min, which can greatly consume the front end of the tungsten wire.
   2. Delicately sharpen the electrode by dipping about 1 mm of the wire tip in and out of the solution at the speed of 2 dips/sec&#....

Results

Single sensillum recording is a powerful investigative technique used in studies of insect chemical ecology and neural physiology. Investigating the neural responses of insects to different volatile compounds, especially those thought to be ecologically related to the survival and development of the insects, not only gives us invaluable insights into the insect olfaction process, but also opens up promising new avenues that could potentially lead to the development of useful new reagents .......

Discussion

The Single Sensillum Recording technique has been extensively used in testing the neural responses of insects such as fruit flies, mosquitoes and bed bugs to different chemical stimuli in the environment. These chemical stimuli are often dissolved and diluted in a common solvent in order to prepare different doses of treatments. However, different solvents can produce quite different release rates for the stimuli. Previous studies on some extensively studied insects such as Drosophila melanogaster, Anopheles.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Tungsten wire	A-M SYSTEMS	#716500	Used for preparing the electrode
KNO2	Sigma	#310484	Used for sharpening the tungsten wire
AC Power Supply	BK Precision	1653A	Providing the voltage in sharpening the tungsten wire
Leica Z6 APO Microscope	Leica	10447424	Used for observing the sensilla on antennae
Simulus controller	Syntech	CS-55	Used for controlling the stimulus application
4-Channel USB Acquisition Controller	Syntech	IDAC-4	Real-time on screen display of all signals before and during recording
Light Source	SCHOTT	A20500	Providing light sources for observation
Micromanupulator	Leica	115378	Used for minor movement of electrode
Speaker	Juster	95a	Connected with Acquisition Controller IDAC-4 and providing sound for the signal
Magnetic stand	Narishige	GJ-1	Used to hold the reference electrode, stablized bed bug and stimulus delivery tube
TMC Vibration Isolation Table	TMC	63-500	Used for isolating the vibration from the equipments
Coverslip	Tedpella	2225-1	Used for holding the bed bug
Double-sided Tape	3M	XT6110	Used for stablizing the bed bug on the coverclip
Dental Wax	Dentakit	DK-R012	Used for supporting the coverclip where bed bug is stablized