Topography of Cones and Rods in the Tree Shrew Retina

J Comp Neurol. 1989 Apr 22;282(4):581-94. doi: 10.1002/cne.902820409.

Abstract

The topographical distribution of cones and rods in the tree shrew retina was analysed quantitatively in whole-mounted retinae and horizontal semithin sections stained with cresyl violet or toluidine blue. The outer nuclear layer consists of a single layer of photoreceptor nuclei with the rod nuclei slightly displaced towards the outer plexiform layer. This facilitated quantification of the photoreceptor populations. The density of cones ranges from 12,000/mm2 in the peripheral retina to a maximum of 36,000/mm2 in the inferior retina. Unlike ganglion cell density, the density of cones does not peak in the temporal retina. Rod density, between 500/mm2 and 3,500/mm2, also peaks in the inferior retina, but not in the same region as cone density. Rods constitute from 1 to 14% of the photoreceptor population, depending on retinal location, and have a local minimum at the central area. Amongst the cones a regularly arrayed subpopulation of presumed blue-sensitive cones is distinguished by its special staining properties. These cones constitute between 4 and 10% of the cone population depending on retinal location. A second, irregularly spaced, subpopulation of possibly pathological cones is also described.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Brain Mapping
  • Female
  • Male
  • Neuroglia / anatomy & histology
  • Photoreceptor Cells / anatomy & histology*
  • Retina / anatomy & histology*
  • Retina / cytology
  • Tupaiidae / anatomy & histology*