THE TAPETUM FIBROSUM IN THE EYES OF TWO SMALL WHALES

Authors

  • NinaM. Young,

    1. Department of Physiology, College of Medicine, University of Florida, Gainesville, Florida 32610.
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    • 4

      Current address: Batelle Marine Laboratory, Duxbury, MA 02332.

  • G. Marion Hope,

    1. Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, Florida 32610.
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  • WilliamW. Dawson,

    1. Department of Physiology, College of Medicine, University of Florida, Gainesville, Florida 32610.
    2. Department of Ophthalmology, College of Medicine, University of Florida, Gainesville, Florida 32610.
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  • RobertL. Jenkins

    1. Marineland of Florida, St. Augustine, Florida 32084
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      Current address: National Aquarium in Baltimore, Baltimore, MD 21202.


Abtract

The pygmy sperm whale (Kogia breviceps) and the bottlenose dolphin (Tursiops truncatus) are equipped with a tapetum fibrosum and, with other Cetacea, are the only carnivores known to possess this typically ungulate tapetal type. Tapeta from two regions of a retina, each with a different spectral reflectance (blue and green), were found to have significantly different fibrillar diameters and inter-fibrillar spacing. When the measured values are applied to a dielectric reflector model, the predicted wavelengths agree with the observed reflectance of the flat-mounted tapeta. The spatial properties of the fibrils change progressively from the tapetal origin in the fibroblast layer to the pigment epithelium, suggesting that different wavelengths may be reflected systematically with tapetal depth. The very large number of reflecting layers characterizing these tapeta, relative to those of other carnivores, may provide for increased spectral purity and efficiency.

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