C. elegans Chemotaxis Assay: A Method to Test Chemosensation in Worms

- To make sense of encountered conditions and respond to them accordingly, the worm C. elegans has, among others, a highly developed chemosensory system able to detect a wide variety of different chemicals.

Sensory neurons in the head, the amphid and inner labial neurons, as well as neurons in the tail, the phasmid neurons, are either directly or indirectly exposed through the cuticle to the outside conditions. These chemosensory neurons code relevant information used by the worm to produce an appropriate behavioral response: a behavior termed chemotaxis.

To test the chemotactic response to either volatile odorants or gustatory water-soluble cues, isolate worms of the desired developmental stage and expose them to the test chemical on a previously prepared experimental arena. When exposed to favorable chemicals like those produced by a bacterial food source, C. elegans displays positive chemotaxis towards the source.

Reversely, when exposed to less favorable or toxic chemicals like heavy metals, the worm displays negative chemotaxis, avoiding the chemical. Hence, olfactory or gustatory mutants fail to avoid aversive chemicals and remain in unfavorable conditions in contrast to wild