Simultaneous presentation of 15°C and sodium chloride to 15°C-cultivated worms at 20°C room temperature. (A and B) Indices of sodium chloride-single presentation (open circle), 15°C-single presentation (open triangle) and simultaneous presentation (closed square). Gray line indicates the sum of the chemotaxis index and the thermotaxis index in single presentations. Each data point is presented as the mean ± SEM. Asterisks indicate significant difference (p < 0.05) between simultaneous presentation index and the summed index. In A, 0.03 M sodium chloride was used. In B, 0.07 M sodium chloride was used. (C and D) Fractions of worms (FRn) every 10 min during simultaneous presentation assay. FRother is fraction in areas other than in the A, B and C regions. Asterisks indicate significant difference (p < 0.05) between FRA and FRB. (E) Track of a single worm under the same conditions as (A). In this example, worms migrated to the region of 15°C first, then to sodium chloride (F) Distribution of tracks of single worms (n = 20). Each track of single worm was recorded for 90 min. High accumulation is indicated by red, and low accumulation is indicated by blue.