Scientists at the University of Hawaiʻi at Mānoa’s Kewalo Marine Laboratory have identified two distinct groups of cells in a marine invertebrate that are like the ciliary photoreceptors responsible for light detection in the human eye.
In the swimming larvae of brachiopods, an ancient group of invertebrate animals, these neural cells are part of a simple two-cell eye that can detect the direction of light and help control the behavior of the animal. One eye cell contains a lens to collect light; the other, pigments to block light coming from behind the eye.
Surprisingly, genes responsible for ciliary photoreception occur at very early stages of embryonic development, before neurons are even formed. Despite the simplicity of the embryos at these stages, they are able to move toward light.
This discovery can serve as a model for the earliest stages in the evolution of the complex human eye, Postdoctoral Researcher Yale Passamaneck and Kewalo Director Mark Martindale write in the March 1, 2011, online journal EvoDevo.