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Fig. 5 | Evolution: Education and Outreach

Fig. 5

From: The Origin of the Vertebrate Eye

Fig. 5

The evolution of vertebrate opsins. The dendrogram shows the relationship between the classes of opsins found not only in our own retinal photoreceptors (retinal opsins) but also in other light-sensing regions; e.g., in the pineal (pinopsin) and elsewhere (encephalopsin) in vertebrates, as well as in the light-sensitive regions of other organisms (e.g., Ciona opsin, and the rhabdomeric opsins of most invertebrates). The primordial opsin had already diverged into three classes (rhabdomeric, “photoisomerase-like,” and ciliary opsins) before protostomes (including most invertebrates) and deuterostome (including vertebrates) diverged, at least 580 Mya. Within the retina of vertebrates, the ciliary opsin diverged into LWS and short-wavelength sensitive branches, with the latter splitting twice more, to give two “SWS” and two “Rh” groups. Originally, all five of these opsins were utilized in cones, and it was not until after the ancestors of lampreys and jawed vertebrates separated (about 500 Mya) that vertebrate rhodopsin (Rh1) became a distinctively “rod opsin” and that the other distinguishing features of rods evolved [From Lamb et al. (2007) Fig. 3; first published in Nature Reviews Neuroscience 8, 2007 © Nature Publishing Group, a division of Macmillan Publishers Limited]

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