Electric Egg-Laying: Effect of Electric Field in a Microchannel onC. elegansEgg-Laying Behavior

Abstract

In this paper, the novel effect of electric field (EF) on adult C. elegans egg-laying in a microchannel is discovered and correlated with neural and muscular activities. The quantitative effects of worm aging and EF strength, direction, and exposure duration on egg-laying is studied phenotypically using egg-count, body length, head movement, and transient neuronal activity readouts. Electric egg-laying rate increases significantly when worms face the anode and the response is EF-dependent, i.e. stronger (6V/cm) and longer EF (40s) exposure result in a shorter egg laying response duration. Worm aging significantly deteriorates the electric egg-laying behaviour with 88% decrease in the egg-count from Day-1 to Day-4 post young-adult stage. Fluorescent imaging of intracellular calcium dynamics in the main parts of the egg-laying neural circuit demonstrate the involvement and sensitivity of the serotonergic hermaphrodite specific neurons (HSNs), vulva muscles, and ventral cord neurons to the EF. HSN mutation also results in a reduced rate of electric egg-laying allowing the use of this technique for cellular screening and mapping of the neural basis of electrosensation in C. elegans. This novel assay can be parallelized and performed in a high-throughput manner for drug and gene screening applications.

Microfluidic Electric Egg-Laying Assay and Application toIn-vivoToxicity Screening of Microplastics usingC. elegans

“…The decrease in worms’ length might also be accompanied by possible changes in the worms’ muscle integrity. In our single-worm egg-laying experiments 28 , we showed that, during EF stimulations, worms contract their bodies in a consistent manner to release eggs. Body shortening was quantified in Figure 4E during the anodal pulses in the multi-worm device for the control and 100mM glucose-fed worms.…”

“…Prior to EF stimulation, a 60 s acclimation period was used during which the flow was stopped by maintaining the inlet and outlet tubes at the same height level. Our previous experiments showed that the anode-facing worms could deposit significantly more eggs 27,35 , highlighting that the worm loading orientation with respect to the EF direction could affect our results. To maintain an equal exposure condition among randomly oriented worms in our device (as shown in Figure 2A), we adopted a new EF stimulation technique in which a series of 5s anodal and 5s cathodal pulses, separated by 25s acclimation periods, was applied for 10 min (Figure 2B).…”

“…The effects of stimulation time and pulsation method on the electric egg-laying behaviour of adult C. elegans. (A) The number of eggs per worm for N=32 worms at 6V/cm using unidirectional pulsation (5s on, 25s off) inside our single-worm device 28 . (B) The total number of eggs deposited at the end of minutes 5 and 10 in (A).…”

“…The microfluidic device shown in Figure 1A was developed to enhance the throughput of our recently reported electric egg-laying method 27,28 , then used for glucose and microplastic toxicity studies. started from a width of 60 µm and narrowed down to different widths of 30, 35, or 40 µm in three different device designs.…”

“…According to our single channel-based egg-laying experiments, an EF of 6 V/cm was needed to maximize egg-laying in C. elegans. 27,35 The required voltage to obtain this EF in the new microfluidic device was estimated to be 34 V using a simple COMSOL Multiphysics simulation ( Figure 1D), as described in the Supplementary file Section S1.…”