TY - JOUR
T1 - A radiographic study of permanent molar development in wild Virunga mountain gorillas of known chronological age from Rwanda
AU - Kralick, Alexandra E.
AU - Loring Burgess, M.
AU - Glowacka, Halszka
AU - Arbenz-Smith, Keely
AU - McGrath, Kate
AU - Ruff, Christopher B.
AU - Chan, King Chong
AU - Cranfield, Michael R.
AU - Stoinski, Tara S.
AU - Bromage, Timothy G.
AU - Mudakikwa, Antoine
AU - McFarlin, Shannon C.
N1 - Funding Information:
The authors gratefully acknowledge the Rwandan government and national parks authorities for permission to work in their country, and for access to mountain gorilla skeletal data for research. The sample utilized in this study is curated by the Mountain Gorilla Skeletal Project in Rwanda, which is indebted to the many field assistants, researchers and other staff of the Rwanda Development Board—Department of Tourism and Conservation, Mountain Gorilla Veterinary Project, and Dian Fossey Gorilla Fund International's Karisoke Research Center, for their tireless efforts toward the preservation of mountain gorilla skeletal remains so they can be made available for study. Without the field and infrastructural support and long-term datasets generated by these organizations, and the participation of numerous staff and students from the National University of Rwanda, the Higher Institute of Agriculture and Animal Husbandry in Rwanda, Institute of National Museums of Rwanda, and academic institutions in the U.S.A., this work would not be possible. The authors also thank Dr. Jordi Galbany, Thadee Muhire and Olive Imanizabayo for their assistance, and Drs. Joost Philippa and Gaspard Nzayisenga for collecting X-rays. They also thank Dr. Jean-Jacques Hublin, Dr. Christophe Boesch, Zewdi Tsegai, David Plotzki, and the staff of the Max Planck Institute for collection and curation of and access to CT scans of P. t. verus specimens. Finally, they thank Drs. Donald Reid and M. Christopher Dean for helpful discussions about great ape dental development, and for their comments on this work. We also appreciate the comments of two anonymous reviewers, which helped improve the manuscript. This research has been made possible by funding to the MGSP by the National Science Foundation (BCS-0852866, BCS-0964944, and BCS-1520221), The Leakey Foundation, National Geographic Society's Committee for Research and Exploration (8486-08), and GW's Center and Institute Facilitating Fund and Academic Excellence support to CASHP. Part of this research was conducted for the senior undergraduate honors thesis of AEK, supported by The George Washington University's Luther Rice Undergraduate Fellowship, Gamow Fellowship, and the Enosinian Scholars Program to AEK, and the helpful feedback of senior thesis committee members Dr. Paul Hoyt-O'Connor and Dr. Bernard Wood. All research was conducted in compliance with all applicable institutional and governmental regulations. Excavation and recovery of specimens for study (SCM, AM, MRC, TSS, TGB, HG, KM, AEK); X-ray and micro-CT imaging of specimens (SCM, AEK, HG, KAS, KM, CBR, KCC, MRC); data collection from radiographs (SCM, AEK, MLB); new wild chimpanzee data (MLB); associated demographic and health data (MRC, TSS, AM); analysis (SCM, AEK, MLB); creation of the radiographic atlas (AEK, KAS, SCM, KM). SCM, AEK, MLB designed the study and wrote the manuscript draft; all authors contributed to interpretation of results and/or editing of the manuscript.
Publisher Copyright:
© 2017 Wiley Periodicals, Inc.
PY - 2017/5
Y1 - 2017/5
N2 - Objectives: While dental development is important to life history investigations, data from wild known-aged great apes are scarce. We report on the first radiographic examination of dental development in wild Virunga mountain gorillas, using known-age skeletal samples recovered in Rwanda. Materials and methods: In 43 individuals (0.0–14.94 years), we collected radiographs of mandibular molars, and where possible, cone beam CT scans. Molar crown and root calcification status was assessed using two established staging systems, and age prediction equations generated using polynomial regression. Results were compared to available data from known-age captive and wild chimpanzees. Results: Mountain gorillas generally fell within reported captive chimpanzee distributions or exceeded them, exhibiting older ages at equivalent radiographic stages of development. Differences reflect delayed initiation and/or an extended duration of second molar crown development, and extended first and second molar root development, in mountain gorillas compared to captive chimpanzees. However, differences in the duration of molar root development were less evident compared to wild chimpanzees. Discussion: Despite sample limitations, our findings extend the known range of variation in radiographic estimates of molar formation timing in great apes, and provide a new age prediction technique based on wild specimens. However, mountain gorillas do not appear accelerated in radiographic assessment of molar formation compared to chimpanzees, as they are for other life history traits. Future studies should aim to resolve the influence of species differences, wild versus captive environments, and/or sampling phenomena on patterns observed here, and more generally, how they relate to variation in tooth size, eruption timing, and developmental life history.
AB - Objectives: While dental development is important to life history investigations, data from wild known-aged great apes are scarce. We report on the first radiographic examination of dental development in wild Virunga mountain gorillas, using known-age skeletal samples recovered in Rwanda. Materials and methods: In 43 individuals (0.0–14.94 years), we collected radiographs of mandibular molars, and where possible, cone beam CT scans. Molar crown and root calcification status was assessed using two established staging systems, and age prediction equations generated using polynomial regression. Results were compared to available data from known-age captive and wild chimpanzees. Results: Mountain gorillas generally fell within reported captive chimpanzee distributions or exceeded them, exhibiting older ages at equivalent radiographic stages of development. Differences reflect delayed initiation and/or an extended duration of second molar crown development, and extended first and second molar root development, in mountain gorillas compared to captive chimpanzees. However, differences in the duration of molar root development were less evident compared to wild chimpanzees. Discussion: Despite sample limitations, our findings extend the known range of variation in radiographic estimates of molar formation timing in great apes, and provide a new age prediction technique based on wild specimens. However, mountain gorillas do not appear accelerated in radiographic assessment of molar formation compared to chimpanzees, as they are for other life history traits. Future studies should aim to resolve the influence of species differences, wild versus captive environments, and/or sampling phenomena on patterns observed here, and more generally, how they relate to variation in tooth size, eruption timing, and developmental life history.
KW - Gorilla beringei beringei
KW - dental development
KW - radiographs
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U2 - 10.1002/ajpa.23192
DO - 10.1002/ajpa.23192
M3 - Article
C2 - 28251607
AN - SCOPUS:85014061055
SN - 0002-9483
VL - 163
SP - 129
EP - 147
JO - American journal of physical anthropology
JF - American journal of physical anthropology
IS - 1
ER -