Fig. 1.

Planarians possess complex ocular photoresponses. The planarian species Schmidtea mediterranea was used to examine ocular behavioral responses to red, green and near-UV wavelengths using our avoidance assay. When approaching a spot of light, three distinct behaviors are observed: worms move through the light (no response), worms avoid the light by moving around it (moderate response) or worms make a 90–180 deg turn away from the light (severe response). Note that worms fail to respond to red light, display moderate responses to green light and have severe responses to near-UV light. N=120 for red, green and near-UV, N=90 for control. Statistics: two sample t-test between percentages; ****P<0.0001 (as compared with no light controls); error bars=s.d.