COUNTS OF GROWTH LAYER GROUPS IN CEMENTUM AND DENTINE IN RINGED SEALS (PHOCA HISPIDA) |
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| Authors: | Robert E A Stewart Barbara E Stewart Ian Stirling Elaine Street |
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| Institution: | Department of Fisheries and Oceans, Freshwater Institute, 501 University Cres., Winnipeg, Manitoba, Canada R3T 2N6;Sila Consultants, Box 38, Group 6, R.R. 1, St. Norbert, Manitoba, Canada R3V 1L2;Canadian Wildlife Service, 5320- 122 Street, Edmonton, Alberta, T6H 3S5 and Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9;Canadian Wildlife Service, 5320- 122 Street, Edmonton, Alberta, Canada T6H 3S5 |
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| Abstract: | We compared counts of growth layer groups (GLGs) in the dentine of un-decalcified, unstained cross-sections and in the cementum of decalcified, stained longitudinal sections of canine teeth from 144 ringed seals ( Phoca hispida ). Although there was a statistically significant correlation until approximately 10 GLGs, about 75% of paired readings at ≤ 10 cementum GLGs disagreed. After 10 GLGs, the number of GLGs in the cementum usually was greater. The maximum GLG count in cementum was 33, compared to a maximum in dentine of only 19. Interobserver differences in median counts were not statistically significant using cementum or dentine counts. Regression analysis revealed that for cementum in female seals, readers differed at higher counts (P < 0.05), and for dentine, there was a constant difference of about 0.6 GLGs ( P < 0.05) for male seals and 1.1 GLGs ( P < 0.05) for female seals. Counting GLGs in the cementum of decalcified and stained longitudinal sections provided higher counts and more agreement between readers, and it was the better of the methods examined for ageing ringed seals. |
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| Keywords: | ringed seal Phoca hispida growth layer group age estimates teeth cementum dentine |
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