  The video showcases how C. elegans worms respond to DC and AC electrical
stimulations. Gabel et al (2007) demonstrated that in the presence of DC and
low frequency AC fields, worms of stage L2 and larger propel themselves towards
the cathode. Rezai et al (2010) have demonstrated that this phenomenon, dubbed
electrotaxis, can be used to control the motion of worms. In the video, we
reproduce Rezai's experimental results. Furthermore, we show, for the first
time, that worms can be trapped with high frequency, nonuniform electric
fields. We studied the effect of the electric field on the nematode as a
function of field intensity and frequency and identified a range of electric
field intensities and frequencies that trap worms without apparent adverse
effect on their viability. Worms tethered by dielectrophoresis (DEP) avoid blue
light, indicating that at least some of the nervous system functions remain
unimpaired in the presence of the electric field. DEP is useful to dynamically
confine nematodes for observations, sort them according to size, and separate
dead worms from live ones.
