porphyropsin
noun
por·phy·rop·sin ˌpȯr-fə-ˈräp-sən 
: a purple pigment in the retinal rods of freshwater fishes that resembles rhodopsin
Word History
Etymology
Greek porphyra purple + English -opsin (as in rhodopsin)
First Known Use
1930, in the meaning defined above
Medical Definition
porphyropsin
noun
por·phy·rop·sin ˌpȯr-fə-ˈräp-sən
: a purple pigment in the retinal rods of freshwater fishes that resembles rhodopsin