Color detecting photoreceptors
Different variant of retinal
- vitamin A1 = > retinal1, vitamin A2 => retinal2 shifts absorption peak 25 nm
- Fish, some amphibians
Change amino acid composition of opsin
- changes absorption peak from 350-620 nm
- Widespread, X-linked in primates
Add colored oil droplet to the photoreceptor cell
- Birds, amphibians, lizards, snakes, turtles