Document Detail

Retinal ganglion cell density of the black rhinoceros (Diceros bicornis): calculating visual resolution.
MedLine Citation:
PMID:  18442443     Owner:  NLM     Status:  MEDLINE    
A single right retina from a black rhinoceros was whole mounted, stained and analyzed to determine the visual resolution of the rhinoceros, an animal with reputedly poor eyesight. A range of small (15-microm diameter) to large (100-microm diameter) ganglion cell types was seen across the retina. We observed two regions of high density of retinal ganglion cells at either end of a long, but thin, horizontal streak. The temporal specialization, which receives light from the anterior visual field, exhibited a ganglion cell density of approximately 2000/mm2, while the nasal specialization exhibited a density of approximately 1500/mm2. The retina exhibited a ganglion cell density bias toward the upper half, especially so, the upper temporal quadrant, indicating that the rhinoceros would be processing visual information from the visual field below the anterior horizon for the most part. Our calculations indicate that the rhinoceros has a visual resolution of 6 cycles/degree. While this resolution is one-tenth that of humans (60 cycles/deg) and less than that of the domestic cat (9 cycles/deg), it is comparable to that of the rabbit (6 cycles/deg), and exceeds that seen in a variety of other mammals including seals, dolphins, microbats, and rats. Thus, the reputation of the rhinoceros as a myopic, weakly visual animal is not supported by our observations of the retina. We calculate that the black rhinoceros could readily distinguish a 30 cm wide human at a distance of around 200 m given the appropriate visual background.
John D Pettigrew; Paul R Manger
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Visual neuroscience     Volume:  25     ISSN:  1469-8714     ISO Abbreviation:  Vis. Neurosci.     Publication Date:    2008 Mar-Apr
Date Detail:
Created Date:  2008-04-29     Completed Date:  2008-05-19     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8809466     Medline TA:  Vis Neurosci     Country:  England    
Other Details:
Languages:  eng     Pagination:  215-20     Citation Subset:  IM    
Queensland Brain Institute, University of Queensland, Australia.
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MeSH Terms
Cell Count
Optic Disk / anatomy & histology
Perissodactyla* / anatomy & histology,  physiology
Retina / cytology,  physiology*
Retinal Ganglion Cells / cytology*,  physiology*
Visual Acuity / physiology*
Visual Fields / physiology

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