GROWTH LAYER GROUPS (GLGs) IN THE TEETH OF AN ADULT BELUKHA WHALE (DELPHINAPTERUS LEUCAS) OF KNOWN AGE: EVIDENCE FOR TWO ANNUAL LAYERS

Authors

  • Arthur D. Goren,

    1. Department of Dentistry, Long Island Jewish-Hillside Medical Center, New Hyde Park, New York 11042
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  • Paul F. Brodie,

    1. Department of Fisheries and Oceans, Marine Ecology Laboratory, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada B2Y 4A2
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  • Stephen Spotte,

    1. Mystic Marinelife Aquarium, Sea Research Foundation, Inc., Mystic, Connecticut 06355 and Department of Biological Sciences, University of Southern Mississippi, Southern Station Box 5018, Hattiesburg, Mississippi 39406
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  • G. Carleton Ray,

    1. Department of Environmental Sciences, University of Virginia, Charlottesville, Virginia 22903
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  • H. W. Kaufman,

    1. Department of Oral Biology and Pathology, School of Dental Medicine, State University of New York at Stony Brook, Stony Brook, New York 11794
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  • A. John Gwinnett,

    1. Department of Oral Biology and Pathology, School of Dental Medicine, State University of New York at Stony Brook, Stony Brook, New York 11794
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  • James J. Sciubba,

    1. Department of Dentistry, Long Island Jewish-Hillside Medical Center New Hyde Park, New York 11042
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  • John D. Buck

    1. Department of Marine Sciences and Marine Sciences Institute, University of Connecticut, Marine Research Laboratory, Noank, Connecticut 06340
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Abstract

Growth layer groups (GLGs) were counted in teeth from an adult male belukha whale (Delphinapterus leucas) that had lived for 23 yr in captivity and was estimated to have been 14 mo at capture. As defined here, GLGs are repeating areas of alternating opaque (denser) and translucent (less dense) dentin or cementurn, or nodes at the dentin-cementum interface. A GLG involves at least one change from opaque to translucent, dense to less dense or ridge to groove, but may be further subdivided by incremental growth layers or laminations. Teeth were prepared by two techniques. Thick sections (longitudinal half sections) were examined with a dissecting microscope under reflected light. Thinner cross and longitudinal sections were x-rayed and the plates scanned with a microdensitometer. Scanning electron photomicrographs were prepared from thick sections, but SEM proved to be the least useful technique. Counts of GLGs were variable because the laminations were numerous and some surface layers had been lost from wear. Thick- and thinner-section techniques gave comparable results, and approximately 40 GLGs were counted consistently. Although captive environments are less variable than natural ones, our findings are further evidence that belukhas in the wild deposit more than one—and probably two—GLGs per year.

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