Egg Laying Assay: A Method to Quantify the Egg-Laying Behavior of C. elegans

- Experiments to quantify egg laying have revealed the neurological components and environmental cues that impact this behavior. Changes in egg laying behavior may indicate toxic effects on the neuromuscular or reproductive systems.

To test for toxicity, raise developmentally-synchronized eggs on nematode growth media plates with and without the compound of interest. These experiments use heat-killed bacterial worm food to prevent the bacteria from metabolizing the compound. Allow this generation to grow until they become young adults.

Then move worms onto new plates under the appropriate control or experimental conditions, and leave them to lay eggs for 24 hours. Each day, transfer the adults to a new plate, and count the eggs on the previous plate. Continue until the adults stop laying, about five days for wild-type worms. Calculate the number of eggs laid per adult worm each day, and add up the total at the end of the experiment.

In the example protocol, we will use the C. elegans egg laying assay to test etoposide-- a chemotherapy drug-- for reproductive toxicity.

- Incubate the age-synchronized eggs on the NGM plate containing DMSO or etoposide at 20 degrees Celsius for 64 hours, until the young adult stage. Transfer five adult worms to new NGM plates without chemicals or new NGM plates containing the same chemical pre-treatment, and incubate them for 24 hours.

Transfer the adults to new NGM plates, as just demonstrated, and count the number of eggs every day. In addition, count the worms that crawled off, died, or were internally hatched. Carry out calculations according to the text protocol.