Sepia Fish Turtle Octopus
“ To suppose that the eye with all its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest degree.” Organs of extreme perfection Organs of extreme perfection Darwin 1882
“ Reason tells me, that if numerous gradations from a simple and imperfect eye to one complex and perfect can be shown to exist, each grade being useful to its possessor, as is certainly the case; if further, the eye ever varies and the variations be inherited, as is likewise certainly the case [...] ” Organs of extreme perfection Organs of extreme perfection Darwin 1882
“ [...] and if such variations should be useful to any animal under changing conditions of life, then the difficulty of believing that a perfect and complex eye could be formed by natural selection, though insuperable by our imagination, should not be considered as subversive of the theory. ” Organs of extreme perfection Organs of extreme perfection Darwin 1882
“ The simplest organ which can be called an eye consists of an optic nerve, surrounded by pigment-cells and covered by translucent skin, but without any lens or other refractive body ” Organs of extreme perfection Organs of extreme perfection Darwin 1882
Planaria torva Planaria torva Gehring 2002
Origins Origins Polyphyletic Multiple origins Monophyletic Single origin
Origins Origins Polyphyletic Multiple origins > 40 Monophyletic Single origin
Designs Designs Fernald 2000
Vertebrate ArthropodCephalopod Polychaete Designs Designs Fernald 2000
Origins Origins Polyphyletic Multiple origins Monophyletic Single origin
Gehring & Ikeo 1999
Human Aniridia Mouse Small eye Fruit fly Eyeless Pax6 Pax6
Paired Box domain Paired Box domain Gehring & Ikeo 1999
Homeodomain Homeodomain Gehring & Ikeo 1999
Pax6 Pax6 Gehring & Ikeo 1999
Ball et al Pax Family Pax Family
Ectopic eyeless Ectopic eyeless
Gehring 2002
Ectopic mouse Pax 6 Ectopic mouse Pax 6 Gehring 2002 LegAntenna
Gehring & Ikeo 1999
Morphology Photopigment stored in apical microvilli Photopigment r-opsin Transcription factors Pax6, ath, brn3, BarH1 Signaling pathway phosphodiesterase G-protein G q-subunit Distribution invertebrate eyes vertebrate retinal ganglion Rhabdomeric PRCs Rhabdomeric PRCs Arendt et al. 2004
Morphology Photopigment stored in membranous folds of cilium Photopigment c-opsin Transcription factors rx Signaling pathway phosphodiesterase G-protein transducin/G i-subunit Distribution vertebrate eyes & pineal invertebrate brain Ciliary PRCs Ciliary PRCs Arendt et al. 2004
Vertebrate ArthropodCephalopod Polychaete Designs Designs Fernald 2000
Platynereis dumerilii Platynereis dumerilii
Larval Adult
Arendt et al Opsins Opsins
Arendt et al Opsins Opsins
Arendt et al Opsins Opsins
Arendt et al r-opsin r-opsin
Arendt et al c-opsin c-opsin
Arendt et al rx rx
Arendt et al bmal bmal