Figure 1. C. elegans frequently reverses at a cliff edge; response is reduced in
mec-3 mutants: A) N2 worm exhibiting precipice response. The worm first encounters the edge of the agar chunk, with its nose going over the edge (left panel). The worm quickly reverses (direction indicated by red arrow) and is shown 1.5 seconds later (right panel). B)
mec-3 worm failing to exhibit precipice response. Upon its first encounter with the edge of the agar chunk (left panel), rather than reversing, this worm continues crawling down the side of the chunk (direction indicated by red arrow) and is shown 1.5 seconds later (right panel). C) Mutant worms with defects in mechanosensation were tested for their precipice response.
mec-3, but neither
mec-10 nor
trp-4, showed a significant decrease in the percentage of worms exhibiting the response. Observers in these experiments were blind to the genotype. Data in C represents % of worms exhibiting precipice response and 95% confidence interval. n = number of worms assayed. *** indicates p < 0.001, based on chi-square test, X2 (1, N=128) = 11.28, p < 0.001. Chi-square test showed no significant difference in the likelihood of precipice response between
mec-10 and N2, X2 (1, N=101) = .79, p = .38, or between
trp-4 and N2, X2 (1, N=106) = 0.13, p = .71. The videos from which the still photos in A and B were taken are available in the Supplemental Materials. Magnification: 250X.