"Lens mitochondria" in the retinal cones of the tree-shrew Tupaia belangeri

Vision Res. 1997 Feb;37(3):267-71. doi: 10.1016/s0042-6989(96)00199-x.


In all mammals, the mitochondria of the cones of the retina are concentrated in the inner segment. Uniquely in tree-shrews (Tupaia, Scandentia, Mammalia), a "megamitochondrion" exhibiting highly specialized systems of densely packed cristae and a very electron dense matrix, is located apically in the inner segment. The ellipsoid is a solid body containing several megamitochondria and, towards its base, a large number of smaller mitochondria. The refractive index of isolated, but not oriented, inner segments of Tupaia belangeri is higher (XA = 1.405) than in any other mammal studied so far. The consistent geometrical pattern of the multilamellar crista-matrix systems, oriented longitudinally towards the outer segment, suggests an additional optical function of the megamitochondria.

MeSH terms

  • Animals
  • Microscopy, Electron
  • Mitochondria*
  • Refractometry
  • Retinal Cone Photoreceptor Cells / chemistry
  • Retinal Cone Photoreceptor Cells / ultrastructure*
  • Tupaia / anatomy & histology*