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Sepia

Sepia. Turtle. Fish. Octopus. Organs of extreme perfection.

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Sepia

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  1. Sepia Turtle Fish Octopus

  2. Organs of extreme perfection “ 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.” Darwin 1882

  3. Organs of extreme perfection “ 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 [...] ” Darwin 1882

  4. Organs of extreme perfection “ [...] 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. ” Darwin 1882

  5. Organs of extreme perfection “ 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 ” Darwin 1882

  6. Planaria torva Gehring 2002

  7. Origins • Polyphyletic Multiple origins • Monophyletic Single origin

  8. Origins • Polyphyletic Multiple origins > 40 • Monophyletic Single origin

  9. Designs Fernald 2000

  10. Designs Vertebrate Arthropod Cephalopod Polychaete Fernald 2000

  11. Origins • Polyphyletic Multiple origins • Monophyletic Single origin

  12. Gehring & Ikeo 1999

  13. Gehring & Ikeo 1999

  14. Pax6 • Human Aniridia • Mouse Small eye • Fruit fly Eyeless

  15. Paired Box domain Gehring & Ikeo 1999

  16. Homeodomain Gehring & Ikeo 1999

  17. Pax6 Gehring & Ikeo 1999

  18. Pax Family Ball et al. 2002

  19. Ectopic eyeless

  20. Ectopic eyeless Gehring 2002

  21. Ectopic mouse Pax 6 Antenna Leg Gehring 2002

  22. Gehring & Ikeo 1999

  23. Rhabdomeric PRCs • Morphology Photopigment stored in apical microvilli • Photopigment r-opsin • Transcription factors Pax6, ath, brn3, BarH1 • Signaling pathway phosphodiesterase • G-protein Gaq-subunit • Distribution invertebrate eyes vertebrate retinal ganglion Arendt et al. 2004

  24. Ciliary PRCs • Morphology Photopigment stored in membranous folds of cilium • Photopigment c-opsin • Transcription factors rx • Signaling pathway phosphodiesterase • G-protein transducin/Gai-subunit • Distribution vertebrate eyes & pineal invertebrate brain Arendt et al. 2004

  25. Designs Vertebrate Arthropod Cephalopod Polychaete Fernald 2000

  26. Platynereis dumerilii

  27. Platynereis dumerilii

  28. Platynereis dumerilii Larval Adult

  29. Opsins Arendt et al. 2004

  30. Opsins Arendt et al. 2004

  31. Opsins Arendt et al. 2004

  32. r-opsin Arendt et al. 2004

  33. c-opsin Arendt et al. 2004

  34. rx Arendt et al. 2004

  35. bmal Arendt et al. 2004

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