Ablation of gon-2 and gtl-1 by RNAi increases the variability of the defecation cycle. Members of the C. elegans TRPM channel gene family were knocked down using RNAi. When gon-2 and gtl-1 are ablated together the variability (C.V.) but not the period is altered. A: The mean period for each population of worms and the mean coefficient of variation (C.V.). Error bars are SEM. B: The period of 15 consecutive defecation cycles for representative controls (a-e) and gon-2(RNAi);gtl-1(RNAi) (f-j) worms.