Retinal topography in the koala (Phascolarctos cinereus)
Schmid, Katrina L., Schmid, Leisa M., Wildsoet, Christine F., & Pettigrew, Jack D. (1992) Retinal topography in the koala (Phascolarctos cinereus). Brain, Behavior And Evolution, 39(1(Print)), pp. 8-16.
Nissl-stained retinal wholemounts were used to investigate the topographical organization of the ganglion cell layer of the koala (Phascolarctos cinereus); the visual resolution limit of this animal was subsequently estimated from retinal ganglion cell density data. Two types of cells could be differentiated on the basis of their size and staining characteristics: a subpopulation of presumed ganglion cells, consisting of medium to large cells with Nissl substance in the cytoplasm and pale uniformly staining nuclei, and a further subpopulation of small, densely staining cells. The latter group were presumed to be neuroglia and displaced amacrine cells. Iso-density contour maps were prepared from total cell counts and also counts of presumed ganglion cells; in all cases, the density of cells was greatest in the inferior retina where there was an area of peak density occurring as a poorly developed, horizontal streak that extended across the inferior retina. The inferior position of the streak in the koala contrasts with reports of the superior position of streaks in other marsupials. Peak cell densities of 2370 cells/mm2 and 1480 cells/mm2 were recorded for the total cell population and the presumed ganglion cell subpopulation, respectively. The latter value is equivalent to a visual resolution of 2.4 cycles/degree, based on sampling theory and a square packing paradigm, placing the koala close in visual performance to two other marsupials, the Australian Northern native cat and the American Virginia opossum.
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|Item Type:||Journal Article|
|Additional Information:||For more information, please refer to the journal's website (see link) or contact the author. Author contact details: firstname.lastname@example.org|
|Keywords:||Evolution, Marsupialia/, anatomy & histology, Retina/, anatomy & histology, Vision/, physiology, Animals, Cell Count, Dark Adaptation/physiology, Male, Optic Disk/anatomy & histology, Retinal Ganglion Cells/ultrastructure, Species Specificity, Visual Acuity/physiology, Visual Fields/physiology|
|Subjects:||Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300)|
|Divisions:||Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
|Copyright Owner:||Copyright 1992 Karger|
|Deposited On:||15 Jun 2006|
|Last Modified:||15 Jan 2009 07:03|
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