#photopigment  a special pigment found in the rods and cones of the retina
  supertype:  pigment  dry coloring matter (especially an insoluble powder to be mixed with a liquid to produce paint etc)
  subtype:  iodopsin  a violet photopigment in the retinal cones of the eyes of most vertebrates; plays a role in daylight vision
  subtype:  visual_purple__rhodopsin__retinal_purple__retinalpurple  a red photopigment in the retinal rods of vertebrates; dissociates into retinene by light

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