Editors' ChoiceEVOLUTION

New Light on the Vertebrate Eye

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Science's STKE  02 Nov 2004:
Vol. 2004, Issue 257, pp. tw401
DOI: 10.1126/stke.2572004tw401

Two types of photoreceptor cell are found in vertebrates and invertebrates. The photosensitive apparatus in vertebrates has a sensory cilium, whereas the compound eye of invertebrates is of the rhabdomeric type. Arendt et al. (see the news story by Pennisi) now examine the evolution of animal eyes by comparing photoreceptor cell types in Bilateria. The vertebrate eye is compared to the primitive polycheate ragworm Platynereis, a modern descendant of the last common ancestor to insects and vertebrates. Platynereis possesses the rhabdomeric photoreceptor cell type but also has a brain structure with the ciliary photoreceptor. Thus, an ancestral brain photosensitive complex may have displayed both rhabdomeric and ciliary types. Furthermore, rhabdomeric photoreceptors of the invertebrate eyes most closely relate to the vertebrate retinal ganglion cells, whereas the rods and cones of the vertebrate retina relate to a population of ciliary photoreceptors located in the invertebrate brain.

D. Arendt, K. Tessmar-Raible, H. Snyman, A. W. Dorresteijn, J. Wittbrodt, Ciliary photoreceptors with a vertebrate-type opsin in an invertebrate brain. Science 306, 869-871 (2004). [Abstract] [Full Text]

E. Pennisi, Worm's light-sensing proteins suggest eye's single origin. Science 306, 796-797 (2004). [Summary] [Full Text]

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