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Any of a class of purple, light-sensitive pigments similar to rhodopsin, found in the retinal rods of the eyes of freshwater fishes and certain frogs.
[Greek porphurā, purple dye, purple garment; see purple + opsin.]
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
(Biochemistry) a purple pigment occurring in the retina of the eye of certain freshwater fishes
[C20: from Greek porphura purple + -opsis + -in, on the model of rhodopsin]
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014