The retina at the back of the eyeball is the tissue containing the photoreceptors and sensory nerve cells that allow vision. The molecules that absorb light energy and initiate vision are photopigments; they are made from proteins combined with compounds called retinoids, which have molecular structures related to vitamin A. The immediate environment of the photoreceptor cells is the interphotoreceptor matrix, which has a complex structure in the vertebrates, and is a region important for retinal physiology, including exchange processes with circulatory fluids. One group of invertebrate animals, the cephalopods, includes squid and octopus with eyes strikingly similar to those in the vertebrates, but with some aspects such as the vitamin-A cycle that seem simpler. We have some knowledge for the vertebrates on how the retinoids are transported in the blood to the retina, and how they are taken up by the photoreceptors to form photopigments. But we know little about whether or not these results are generalizable to the wide diversity of visual systems in other animal classes. This study will utilize biochemistry and electron microscopy on octopus retina to identify the presence and location of cellular receptor sites on the photoreceptors for binding retinoids. The substructure of the interphotoreceptor matrix also will be studied by staining techniques. These data will provide the first data on these important features of invertebrate eyes, and will be important to compare to the known features of the vertebrate eye. The inclusion of undergraduates including minorities in this technically modern and productive laboratory will have a very high impact on the recruitment and retention of young scientists in this field.
