Nose touch avoidance behavior is primarily mediated by ASH neuron in different species of nematodes. Data are represented as mean percent avoidance and error bars indicate standard error of mean (s.e.m). (See Supplementary Materials and Methods in Additional file 1 for details). Presence and absence of neurons is denoted by '+' and '-', respectively. For unablated and ablated conditions, n = 30 and n = 10 animals, respectively. (A) Most species exhibit similar avoidance responses when challenged with a mechanosensory stimulus. Ablation of the ASH neurons results in reduction of nose touch avoidance in all species. In Caenorhabditis sp. 3 (PS1010), ASH ablation results in complete abolishment of nose touch response compared with ASH ablated animals in Caenorhabditis elegans. Mean percent avoidance of different species was compared using ANOVA. P values are denoted as follows: ***, P < 0.001. (B) FLP and OLQ neurons do not mediate nose touch response in Caenorhabditis sp. 3. In C. elegans, FLP-ablated animals were significantly different than unablated animals. ASH/FLP-ablated animals were significantly different than ASH-ablated animals. OLQ ablations did not affect nose touch in C. elegans. Ablation of FLP/OLQ had significantly lower nose touch response than either of the single ablated animals. Ablations of ASH/FLP/OLQ-ablated animals had significantly lower response than ASH-ablated animals but were similar in response to ASH/FLP-ablated animals in C. elegans. In Caenorhabditis sp. 3, FLP-ablated animals were not significantly different than unablated animals (P > 0.05). There were no significant differences in nose touch avoidance between ASH-ablated, FLP/ASH-ablated, and ASH/FLP/OLQ-ablated animals (P > 0.05). Other ablations tested for statistical significance: ASH-ablated vs. unablated animals, P < 0.001; FLP-ablated vs. ASH/FLP-ablated, P < 0.001; FLP-ablated vs. FLP/OLQ-ablated, P < 0.01; OLQ-ablated vs. FLP/OLQ-ablated, P < 0.001. P values were generated by ANOVA and denoted as follows: **, P < 0.01; ***, P < 0.001.