Aging steller sea lions by growth layer groups in teeth
ABSTRACT Accurate age determination of individuals is crucial in estimating age structure in populations as well as age‐specific rates of reproduction and survival. We examined growth layer groups (GLGs) in the canine, incisor, and postcanine teeth of Steller sea lions (Eumetopias jubatus) to find t...
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Wiley
2019-06-01
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| Series: | Wildlife Society Bulletin |
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| Online Access: | https://doi.org/10.1002/wsb.965 |
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| author | Takeomi Isono Yumi Kobayashi Vladimir N. Burkanov Orio Yamamura |
| author_facet | Takeomi Isono Yumi Kobayashi Vladimir N. Burkanov Orio Yamamura |
| author_sort | Takeomi Isono |
| collection | DOAJ |
| description | ABSTRACT Accurate age determination of individuals is crucial in estimating age structure in populations as well as age‐specific rates of reproduction and survival. We examined growth layer groups (GLGs) in the canine, incisor, and postcanine teeth of Steller sea lions (Eumetopias jubatus) to find the optimal method to determine their age using 18 known‐age animals, from data collected in Hokkaido, Japan, 1995–2011. After checking to determine if the pulp cavity was open, nearly closed, or closed, teeth were sectioned and stained. Occlusion of the canine pulp cavity occurred at older ages than with the incisor and postcanine teeth. Initially, the number of GLGs in both dentin and cementum was compared with actual ages to confirm the age determination method. Dentin GLGs appeared clearly in all of the canines, incisors, and postcanines. The number of GLGs was consistent with the actual age, with the exception of teeth with a closed pulp cavity. With respect to cementum, appearance of GLGs was rather obscure and no GLG was detectable at ages of 0 and 1 year. Thus, the number of GLGs in cementum could be assigned as age when the value 1 year was added. We examined the accuracy and precision of the tested methods using an independent reader, who did not know the actual ages. By conducting readings 3 times, we used coefficient of variation (CV) to determine precision. The most precise CV was obtained in dentin canine (6.7%). Accuracy was calculated as proportion of estimates without error. The greatest accuracy in dentin was observed in canines (0.83, n = 18), whereas that of cementum was in postcanines (0.36, n = 11). We concluded that canine dentin provided the most precise and accurate ages for Steller sea lions. Once closure of the pulp cavity in canines has occurred at the age of 15–16 years in males and 11–12 years in females, we recommend postcanine cementum be used. © 2019 The Wildlife Society. |
| format | Article |
| id | doaj-art-1c43688f98644f8c81f8f351fa70eab1 |
| institution | DOAJ |
| issn | 2328-5540 |
| language | English |
| publishDate | 2019-06-01 |
| publisher | Wiley |
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| series | Wildlife Society Bulletin |
| spelling | doaj-art-1c43688f98644f8c81f8f351fa70eab12025-08-20T02:49:15ZengWileyWildlife Society Bulletin2328-55402019-06-0143223824310.1002/wsb.965Aging steller sea lions by growth layer groups in teethTakeomi Isono0Yumi Kobayashi1Vladimir N. Burkanov2Orio Yamamura3Fisheries Management Department, Hokkaido National Fisheries Research Institute Japan Fisheries Research and Education Agency 116 Katsurakoi Kushiro Hokkaido 085‐0802 JapanDivision of Marine Bio‐resource and Environmental Science Graduate School of Fisheries Sciences, Hokkaido University 3‐1‐1 Minato‐Cho Hakodate Hokkaido 041‐8611 JapanMarine Mammal Laboratory Alaska Fisheries Science Center/National Oceanic and Atmospheric Administration Seattle WA 98115 USAFisheries Management Department, Hokkaido National Fisheries Research Institute Japan Fisheries Research and Education Agency 116 Katsurakoi Kushiro Hokkaido 085‐0802 JapanABSTRACT Accurate age determination of individuals is crucial in estimating age structure in populations as well as age‐specific rates of reproduction and survival. We examined growth layer groups (GLGs) in the canine, incisor, and postcanine teeth of Steller sea lions (Eumetopias jubatus) to find the optimal method to determine their age using 18 known‐age animals, from data collected in Hokkaido, Japan, 1995–2011. After checking to determine if the pulp cavity was open, nearly closed, or closed, teeth were sectioned and stained. Occlusion of the canine pulp cavity occurred at older ages than with the incisor and postcanine teeth. Initially, the number of GLGs in both dentin and cementum was compared with actual ages to confirm the age determination method. Dentin GLGs appeared clearly in all of the canines, incisors, and postcanines. The number of GLGs was consistent with the actual age, with the exception of teeth with a closed pulp cavity. With respect to cementum, appearance of GLGs was rather obscure and no GLG was detectable at ages of 0 and 1 year. Thus, the number of GLGs in cementum could be assigned as age when the value 1 year was added. We examined the accuracy and precision of the tested methods using an independent reader, who did not know the actual ages. By conducting readings 3 times, we used coefficient of variation (CV) to determine precision. The most precise CV was obtained in dentin canine (6.7%). Accuracy was calculated as proportion of estimates without error. The greatest accuracy in dentin was observed in canines (0.83, n = 18), whereas that of cementum was in postcanines (0.36, n = 11). We concluded that canine dentin provided the most precise and accurate ages for Steller sea lions. Once closure of the pulp cavity in canines has occurred at the age of 15–16 years in males and 11–12 years in females, we recommend postcanine cementum be used. © 2019 The Wildlife Society.https://doi.org/10.1002/wsb.965age determinationagingcementumdentinEumetopias jubatusgrowth layer groups |
| spellingShingle | Takeomi Isono Yumi Kobayashi Vladimir N. Burkanov Orio Yamamura Aging steller sea lions by growth layer groups in teeth Wildlife Society Bulletin age determination aging cementum dentin Eumetopias jubatus growth layer groups |
| title | Aging steller sea lions by growth layer groups in teeth |
| title_full | Aging steller sea lions by growth layer groups in teeth |
| title_fullStr | Aging steller sea lions by growth layer groups in teeth |
| title_full_unstemmed | Aging steller sea lions by growth layer groups in teeth |
| title_short | Aging steller sea lions by growth layer groups in teeth |
| title_sort | aging steller sea lions by growth layer groups in teeth |
| topic | age determination aging cementum dentin Eumetopias jubatus growth layer groups |
| url | https://doi.org/10.1002/wsb.965 |
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