Electrotaxis Assay: A Method to Observe Locomotion in C. elegans

- Without sensory stimuli, C. elegans movement is generally forward and is interrupted by reversals and turns-- random reorienting maneuvers that result in a change of direction. C. elegans are electroreceptive. That is, they can sense electric fields. When exposed to a mild direct current or DC, worms move in a straight uninterrupted path in the direction of the negative electrode or cathode, a behavior termed electrotaxis.

To more accurately observe the worm's locomotion, place the animal in a microfluidic device and apply a DC electric field. Reverse the direction of the field, and the worm will turn the opposite way-- towards the direction of the cathode. Apply an alternating current, AC, and the worm will stop. The alternating change in the field's direction overwhelms the worm's neuromotor systems, resulting in the worm's immobilization. Reapply the DC field, and the worm will resume forward motion towards the cathode.

In the following example protocol, we will see a setup demonstrating an electrotaxis assay in a microfluidic device.

- Begin this step by placing the just assembled micro-channel onto an xy- movable stage of a microscope with a mounted camera connected to a mon