Early Metamorphic Insertion Technology for Insect Flight Behavior Monitoring

Summary

We present a novel surgical procedure to implant electrodes in Manduca sexta during its early metamorphic stages. This technique allows mechanically stable and electrically reliable coupling with the neuromuscular tissue to study flight neurophysiology dynamics. We also present a novel magnetic levitation platform for tethered studies of insect yaw.

Abstract

Early Metamorphosis Insertion Technology (EMIT) is a novel methodology for integrating microfabricated neuromuscular recording and actuation platforms on insects during their metamorphic development. Here, the implants are fused within the structure and function of the neuromuscular system as a result of metamorphic tissue remaking. The implants emerge with the insect where the development of tissue around the electronics during pupal development results in a bioelectrically and biomechanically enhanced tissue interface. This relatively more reliable and stable interface would be beneficial for many researchers exploring the neural basis of the insect locomotion with alleviated traumatic effects caused during adult stage insertions. In this article, we implant our electrodes into the indirect flight muscles of Manduca sexta. Located in the dorsal-thorax, these main flight powering dorsoventral and dorsolongitudinal muscles actuate the wings and supply the mechanical power for up and down strokes. Relative contraction of these two muscle groups has been under investigation to explore how the yaw maneuver is neurophysiologically coordinated. To characterize the flight dynamics, insects are often tethered with wires and their flight is recorded with digital cameras. We also developed a novel way to tether Manduca sexta on a magnetically levitating frame where the insect is connected to a commercially available wireless neural amplifier. This set up can be used to limit the degree of freedom to yawing “only” while transmitting the related electromyography signals from dorsoventral and dorsolongitudinal muscle groups.

Introduction

Inserting electrodes, even with attached electronic systems to insects for telemetric recording applications, has been a major method to understand how neural systems function during natural flight ¹. Attaching or implanting artificial systems in insects has posed many challenges involving the potential to disturb the natural flight of the insect. Superficial attachment or surgical insertion of artificial platforms on the adult insect is unreliable due to possible shifting of the inserted devices caused by body-induced inertial and stress forces. Superficially attached or surgically inserted electrodes are also prone to be rejected by the insects as a forei....

Protocol

NOTE: The source of the materials and reagents required to follow the protocol is provided in the “Reagents” Table below.

1. Preparing Printed Circuit Boards (PCBs) for Recording Electrode Connection

NOTE: In order to provide a practical experimental procedure, wire electrodes are soldered to a PCB to insert these electrodes into an FFC (flexible flat cable) connector.

1. Cut a 0.5x5 cm² piece of copper clad laminate.
2. Using a fine tip marker, draw three 0.1x5cm² rectangle pads as etching mask patterns.
3. Etch the exposed laminate using a PCB etchant ins....

Results

A schematic of the overall EMIT procedure is presented in Figure 1, showing the major stages in the hawkmoth’s metamorphic cycle and the corresponding electrode insertion steps. The electrode insertion should be performed in the late pupal stage 4 to 7 days before eclosion. This allows the muscle fibers to develop around the electrodes and secure the implant in the insect.

The typical result of a completed late pupal stage insertion where the two active electrodes and the grou.......

Discussion

There are several critical steps during the surgical insertion of the recording electrodes that affect the ability to record data in the later steps of the protocol. The recording electrodes should be inserted into the pupa one day after exhibiting wing spots on its dorsal side. If the insertion is performed two or more days after this time, the insect’s tissue will not have enough time to develop around and stabilize the inserted electrodes. This could lead to movement of the implanted electrodes and unreliable re.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Coated stainless steel wire	A-M Systems	791900	0.008’’ bare, 0.011’’ coated, annealed
Flexible electrode wire			Litz or inductor wire can be used.
Surface-mount FFC connector	Hirose Connector	FH28E-20S-0.5SH(05)
Tweezers	Grobet USA		Clean with 70% alcohol before use on the insect.
Kim-Wipes	Kimberly-Clark Worldwide	34155	Any size delicate-wipe tissues can be used.
Teflon tape			5 mm width Teflon tape.
Hypodermic Needle	Becton Dickinson & Co.	30511	20-30 G hypodermic needle can be used. Video showed 30 G.
Rigid fixation stick			Variety of materials can be used (e.g., coffee stirrers)
Insect emergence cage			Plastic pet cage lined with packing paper or similar padding. Ventilation holes are needed.
Thermal cauterizer	Advanced Meditech International	CH-HI CT2103 (tip)	Optional equipment used for application of dental wax.
Dental wax	Orthomechanics LC., Broken Arrow, Oklahoma		Optional material used for stabilizing the electrodes on the insect.
Magnetic levitation platform			Custom designed frame fabricated in-house with 3D prototyping.