Fig. 2.

Map of the behavioral responses to tactile stimulation along the length of the leech body in various water depths. Top panel: responses on a moist plexiglass surface (water depth=0x) to tactile stimulation on the dorsal surface, in the center of somatic segments 3–19 and at the midpoints between the segments. Bottom panels: responses to tactile stimulation at somatic segments 3–19 while immersed in water at four depths (0.5x, 1x, 2x and 4x) relative to the leech's dorsoventral thickness at its most relaxed length (n=14, mean=2.4±0.53 mm). Because there were usually a few ‘other’ responses (Cornford et al., 2006) or no response to some stimuli, the percent totals for each segment may not add up to 100. In the four water depths of 0.5x, 1x, 2x and 4x, we stimulated in the middle of each segment but not between segments. LB, local bending; WBS, whole-body shortening.