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