How to prevent worms from escaping from plates?

Hi everyone,

Has anybody in this community had extensive experience with performing behavioural assays or experiments on C. elegans that require the worm(s) to stay put?
One of the experiments I’ve been carrying out, a chronic aldicarb assay, entails subjecting solitary larval stage worms to low (relatively) concentrations of aldicarb present in the NGM agar, and assaying the number of progeny present after 3 days.

Unfortunately, some of the worms attempt to escape from their plates and can be found halfway up the side, desiccated and usually dead, despite the presence of bacteria in the plate centre.

I was wondering if anyone knows of an effective way that would prevent a worm from escaping from its plate?


I don’t have personal experience, but I know of one standard method, which is to paint a ring of high osmolarity around the edge of the plate (examples include Sawin et al and Dong et al).

Reading through the papers it looks quite promising so I’ll give it a try. Hopefully none of the unc mutants I’m using are osmotic insensitive.

Thank you for the suggestion.


Hinrich Schulenburg has developed special “balls” which are covered from the inside with NGM. In this way the worms can never escape. Very neat. see


Hey, folks. You could try using 10 mg palmitic acid/mL ethanol. After adding around 30 uL to the rim of a medium plate, for example, and rolling it along the side, the palmitic acid should dry nicely and create a physical barrier to the worms.