Of these three groups, only primates have additionally evolved trichromatic color vision via duplication of the ancestral long-wavelength sensitive opsin, an event which occurred only 25 to 30 million years ago [39].
This is of particular interest because the pancrustaceans (hexapods+crustaceans) have more optical designs than any other major clade of animals, allowing us to test specifically whether the high amount of disparity in pancrustacean eyes is correlated with a higher rate of duplication and retention of vision genes.
Diurnal mammals generally have a well-developed visual system, and this is particularly advanced in Old World monkeys, which have obtained trichromatic color vision via a gene duplication event (Surridge et al. 2003).
Nathans and others demonstrated that humans, chimps, and gorillas evolved red-green color vision via an opsin gene duplication event, so I wanted know if butterflies evolved red-green color vision through a similar genetic mechanism".
Both lines of evidence suggest that the VNO became nonfunctional at the same time in primate evolution that trichromatic color vision evolved via a gene duplication of the green/red opsin gene (Liman and Innan 2003).
The presence of multiple paralog pairs of similar age is strong evidence of a large-scale duplication event (e.g., Wolfe and Shields 1997; Vision et al. 2000; McKain et al. 2012).
Research suggests that a gene duplication event, similar to the one that produced color vision in primates--humans, chimps, and gorillas--may have occurred in butterflies.
In fishes, the evolution of color vision has been directed by opsin gene duplication and diversification, pseudogenization and differential gene expression [ 11].
The single (most likely visual) r-opsin found in H. dujardini supports the hypothesis of monochromatic vision in the panarthropod ancestor, whereas two duplications of the ancestral panarthropod c-opsin have led to three c-opsins in tardigrades.
The eyes of flower-visiting butterflies are often spectrally highly complex with multiple opsin genes generated by gene duplication, providing an interesting system for a comparative study of color vision.
