Fig. 3. Responses to large (2 cm wide) obstacles by T. cystophora. The medusae performed clear avoidance responses to the colored obstacles but not to the transparent ones (A–C, N=10). There were no significant differences between the colored obstacles in avoidances per minute and contacts per minute (A,B). The red obstacle induced avoidance responses significantly further away than from any of the other obstacles (C, ^**Fisher's PLSD, P0.0001). Values are means and error bars indicate s.e.m. Trans, transparent obstacle; Trans+B, transparent obstacle with black top above water.