“Did the Eye Evolve Once or Multiple Times? Evidence from Conserved Characteristics of Ocular Refractive Development”. Presentation by Dr. Jake Sivak (UWaterloo)

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Date(s) - 20/03/2019
3:00 pm - 4:00 pm

KATZ Building, Room 7-003


It has been speculated that the unitary eyes of vertebrates and molluscs, and the compound eyes of insects and crustaceans, evolved separately.  On the other hand, the common use of rhodopsin as a photoreceptor molecule, and the conservation of Pax6 as a master control gene for eye development, suggest instead that the eye evolved once.  An alternative approach to the question of eye evolution involves the comparative analyses of physiological optics.  Serendipitous discoveries involving form deprivation and defocus with young monkeys and chicks demonstrated the importance of visual experience on eye development.  Similar results have been demonstrated in fish, despite differences in ocular anatomy, physiology and optics.  In particular, since fish grow throughout life, these effects can also be demonstrated in adults.  The cephalopod eye is an often-cited example of convergent evolution in comparison with the vertebrate eye, although considerable developmental differences exist.  Nevertheless, squid eyes from animals raised under light of varying wavelengths exhibit the same anatomical and refractive changes found with vertebrates. These observations provide support for the view that the eye evolved once.  Moreover, because of their very compressed lifespans (only one to two years) cephalopods may be ideal animal models for the study of ocular refractive development.