Planarian Photophobic Responses Vary by Wavelength.

(A) Images of the photophobia assay showing single trials (one group, n = 6) for control (ambient light, left) and UV 360 (right) wavelengths. All worms begin in quadrant 1 (Q1, red circles). While control worms randomly explore the dish, in UV 360 trials worms move rapidly away from the light (white circles). Images enhanced for visualization. (B) Graph showing overall photophobic responses for each wavelength, as measured by worm location in each of the four quadrants (Q1–Q4) after 2 minutes. Photophobic responses are indicated by increased presence in Q4 (black bars) which is farthest from the light. Significance (asterisks = p<0.001 as compared to controls) was calculated by Mann-Whitney (with Dunn’s Q), which takes into account worm location across all four quadrants simultaneously. Red dashed line = average control value.