RT Journal Article SR Electronic T1 C. elegans discriminate colors without eyes or opsins JF bioRxiv FD Cold Spring Harbor Laboratory SP 092072 DO 10.1101/092072 A1 D. Dipon Ghosh A1 Xin Jin A1 Michael Nitabach YR 2017 UL http://biorxiv.org/content/early/2017/11/17/092072.abstract AB Here we establish that, contrary to expectations, Caenorhabditis elegans nematode worms possess a color discrimination system despite lacking any opsin or other known visible light photoreceptor genes. We found that white light guides C. elegans foraging decisions away from harmful bacteria that secrete a blue pigment toxin. Absorption of amber light by this blue pigment toxin alters the color of light sensed by the worm, and thereby triggers an increase in avoidance. By combining narrow-band blue and amber light sources, we demonstrated that detection of the specific blue:amber ratio by the worm guides its foraging decision. These behavioral and psychophysical studies thus establish the existence of a color detection system that is distinct from those of other animals.