The pheromone drop test is a simple and robust behavioral assay to quantify acute avoidance of pheromones inC. elegans, and the suppression of avoidance by attractive pheromones. In the pheromone drop test, water-solubleC.eleganspheromones are individually applied to animals that are freely moving on a large plate. Upon encountering a repellent, eachC. elegansanimal may or may not try to escape by making a long reversal. The fraction of animals that make a long reversal response indicates the repulsiveness of a given pheromone to a specific genotype/strain ofC. elegans. Performing the drop test in the presence of bacterial food enhances the avoidance response to pheromones. Attraction to pheromones can be assayed by the suppression of reversals to repulsive pheromones or by the suppression of the basal reversal rate to buffer.
