scholarly journals The biology behind the counts: tooth development related to age estimation in beluga (Delphinapterus leucas)

2014 ◽  
Vol 8 ◽  
Author(s):  
Barbara E Stewart ◽  
Robert EA Stewart
Keyword(s):  
Tooth Development ◽  
Delphinapterus Leucas ◽  
Key Factors ◽  
Growth Layer ◽  
Diagnostic Features ◽  
Developmental Factors ◽  
Occlusal Wear ◽  
Layer Groups ◽  
Pulp Stones ◽  
Age Estimates

The widely accepted method of determining ages of beluga is to count dentine growth layer groups (GLGs) in median, longitudinal sections of a tooth. It is essential to understand how these growth layers form and to consider developmental factors that can confound their enumeration to be able to provide meaningful age estimates. Here we provide information on, and illustrate, the developmental biology of beluga teeth as it relates to interpreting GLGs. Key factors are: evaluating the presence and occlusal wear of fetal dentine; interpreting early-formed diagnostic features such as the neonatal line; assessing the last-formed growth layer adjacent to the pulp cavity; identifying the presence of nodes at the dentine-cementum interface to assist in counting GLGs; and recognizing  pulp stones and accessory lines in the dentine which may hinder the age estimate process.

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

1987 ◽  
Vol 3 (1) ◽  
pp. 14-21 ◽  
Author(s):  
Arthur D. Goren ◽  
Paul F. Brodie ◽  
Stephen Spotte ◽  
G. Carleton Ray ◽  
H. W. Kaufman ◽  
...  
Keyword(s):  
Delphinapterus Leucas ◽  
Growth Layer ◽  
Layer Groups

scholarly journals Accuracy, precision, and error in age estimation of Florida manatees using growth layer groups in earbones

2019 ◽  
Vol 100 (4) ◽  
pp. 1350-1363 ◽  
Author(s):  
Gina L Lonati ◽  
Amber R Howell ◽  
Jeffrey A Hostetler ◽  
Paul Schueller ◽  
Martine de Wit ◽  
...  
Keyword(s):  
Age Estimation ◽  
Wildlife Conservation ◽  
Absolute Error ◽  
Large Sample Size ◽  
Growth Layer ◽  
Florida Manatee ◽  
Data Set ◽  
Photo Identification ◽  
Layer Groups ◽  
Age Estimates

AbstractAges of Florida manatees (Trichechus manatus latirostris) can be estimated by counting annual growth layer groups (GLGs) in the periotic dome portion of the tympanoperiotic complex of their earbones. The Florida Fish and Wildlife Conservation Commission manages an archive of more than 8,700 Florida manatee earbones collected from salvaged carcasses from 1989 to 2017. Our goal was to comprehensively evaluate techniques used to estimate age, given this large sample size and changes to processing protocols and earbone readers over time. We developed new standards for estimating ages from earbones, involving two independent readers to obtain measurements of within- and between-reader precision. To quantify accuracy, precision, and error, 111 earbones from manatees with approximately known ages (first known as calves: “KAC”) and 69 earbones from manatees with minimum known ages (“MKA,” based on photo-identification sighting histories) were processed, and their ages were estimated. There was greater precision within readers (coefficient of variation, CV: 2.4–8.5%) than between readers (CV: 13.1–13.3%). The median of age estimates fell within the true age range for 63.1% of KAC cases and was at least the sighting duration for 75.0% of MKA cases. Age estimates were generally unbiased, as indicated by an average raw error ± SD of −0.05 ± 3.05 years for the KAC group. The absolute error (i.e., absolute value of raw error) of the KAC data set averaged 1.75 ± 2.50 years. Accuracy decreased and error increased with increasing known age, especially for animals over 15 years old, whose ages were mostly underestimated due to increasing levels of resorption (the process of bone turnover that obscures GLGs). Understanding the degree of uncertainty in age estimates will help us assess the utility of age data in manatee population models. We emphasize the importance of standardizing and routinely reviewing age estimation and processing protocols to ensure that age data remain consistent and reliable.

Bomb radiocarbon dating calibrates beluga (Delphinapterus leucas) age estimates

2006 ◽  
Vol 84 (12) ◽  
pp. 1840-1852 ◽  
Author(s):  
R.E.A. Stewart ◽  
S.E. Campana ◽  
C.M. Jones ◽  
B.E. Stewart
Keyword(s):  
Atomic Bomb ◽  
Growth Increment ◽  
Delphinapterus Leucas ◽  
Age Validation ◽  
Bomb Radiocarbon ◽  
Beluga Whale Delphinapterus Leucas ◽  
Layer Groups ◽  
Free Ranging ◽  
Accurate Indicator ◽  
Age Estimates

The ages of many mammals are estimated by counting growth layers in tooth sections, yet validation of age estimation techniques using free-ranging mammals has been problematic. Contrary to age estimates for most other animals in which it is assumed that one bipartite growth increment forms annually, beluga whale ( Delphinapterus leucas (Pallas, 1776)) age estimates have been calculated assuming that two growth layer groups (GLGs) form each year. Here we report the age validation for belugas based on date-specific incorporation of atomic bomb radiocarbon into tooth GLGs. Radiocarbon assays of dentinal layers formed in belugas harvested between 1895 and 2001 indicated that radiocarbon from atmospheric testing of nuclear weapons was incorporated into growing teeth and retained for the remaining life of the animal. Comparison of age determined by bomb radiocarbon with age determined by GLG counts indicated that GLGs form annually, not semiannually, and provide an accurate indicator of age for belugas up to at least 60 years old. Radiocarbon signatures of belugas were temporally and metabolically stable and were apparently derived more from the radiocarbon content of their prey than from water. Our understanding of many facets of beluga population dynamics is altered by the finding that this species lives twice as long as previously thought.

A comparison of age determination techniques for the harbour porpoise, Phocoena phocoena L.

1989 ◽  
Vol 67 (7) ◽  
pp. 1832-1836 ◽  
Author(s):  
Peter Watts ◽  
David E. Gaskin
Keyword(s):  
North Atlantic ◽  
Age Determination ◽  
Harbour Porpoise ◽  
Phocoena Phocoena ◽  
Growth Layer ◽  
Single Cross Section ◽  
Living Bone ◽  
Layer Groups ◽  
Annual Deposition ◽  
Age Estimates

The maximum life-span of the harbour porpoise has been estimated at 13 years (based upon dentinal growth layer groups in the teeth) and at 21 years (based upon growth layers in the periosteal bone of the mandible). We used both techniques to estimate the ages of 120 harbour porpoises from the western North Atlantic, in an attempt to determine the relative reliability of each technique. Dentinal layering was the better predictor of body length. Mandibular layering was highly variable even within a single cross section in most specimens, as a result of both common bifurcation of the layers and destruction of the inner layers by growth and remodelling of the living bone. Furthermore, mandibular layers appear to be deposited at a rate of 2 layers/year, double the deposition rate of dentinal growth layer groups. Age estimates which assume annual deposition of mandibular layers therefore overestimate true age.

scholarly journals Inter-lab comparison of precision and recommended methods for age estimation of Florida manatee (Trichechus manatus latirostris) using growth layer groups in earbones

2016 ◽  
Vol 8 ◽  
Author(s):  
Katherine Brill ◽  
Miriam Marmontel ◽  
Meghan Bolen-Richardson ◽  
Robert EA Stewart
Keyword(s):  
Age Estimation ◽  
Effective Management ◽  
Growth Layer ◽  
Florida Manatee ◽  
Trichechus Manatus ◽  
Trichechus Manatus Latirostris ◽  
Apparent Source ◽  
Layer Groups ◽  
Age Estimates ◽  
Good Agreement

Manatees are routinely aged by counting Growth Layer Groups (GLGs) in periotic bones (earbones). Manatee carcasses recovered in Florida between 1974 and 2010 provided age-estimation material for three readers and formed the base for a retrospective analysis of aging precision (repeatability). All readers were in good agreement (high precision) with the greatest apparent source of variation being the result of earbone remodelling with increasing manatee age. Over the same period, methods of sample preparation and of determining a final age estimate changed. We examined the effects of altering methods on ease of reading GLGs and found no statistical differences. Accurate age estimates are an important component for effective management of the species and for better models of population trends and we summarize the currently recommended methods for estimating manatee ages using earbones. 

Ageing live New Zealand sea lions (Phocarctos hookeri) using the first post-canine tooth

2004 ◽  
Vol 31 (2) ◽  
pp. 177 ◽  
Author(s):  
S. Childerhouse ◽  
G. Dickie ◽  
G. Hessel
Keyword(s):  
New Zealand ◽  
Age Estimation ◽  
Growth Layer ◽  
Canine Tooth ◽  
Sea Lions ◽  
Glass Slides ◽  
Significant Difference ◽  
Layer Groups ◽  
Phocarctos Hookeri ◽  
Age Estimates

Live New Zealand sea lions (Phocarctos hookeri) were aged from growth layer groups (GLGs) in the cementum of a lower first post-canine tooth. A single post-canine (PC1) was removed from individuals of known-age (n = 74) between 1997 and 2001 while under a full anaesthetic. Teeth were decalcified, sectioned on a cryostat, stained and then mounted on glass slides. Age was estimated by counting GLGs in the cementum multiple times. Age estimates were calibrated with known-aged individuals and confirmed the annual formation of cementum annuli in PC1 tooth. While there is some variation in assigning exact age to individuals, it was possible to age 94% of teeth to the exact year or to within 1 year of actual age. There was no significant difference in the slope of regression lines associated with actual and estimated age using this technique (t-test, t = 0.309, d.f. = 144, P < 0.05). Accuracy in ageing was improved by discarding sets of readings with low precision and re-reading the tooth until a precise set of estimates was made. GLGs in the cementum were more accurate and robust for age estimation than using GLGs in the dentine. This paper describes a reliable method for the preparation and ageing of the first post-canine tooth (PC1) from live New Zealand sea lions.

scholarly journals Growth of the skull of the bottlenose dolphin, Tursiops truncatus, in the Southwest Atlantic Ocean

10.5597/00229 ◽  
2017 ◽  
Vol 11 (1-2) ◽  
pp. 199-211 ◽  
Author(s):  
André Silva Barreto
Keyword(s):  
Bottlenose Dolphin ◽  
Tursiops Truncatus ◽  
Growth Equation ◽  
Growth Layer ◽  
Southwest Atlantic ◽  
Development Patterns ◽  
Skull Measurements ◽  
The One ◽  
Layer Groups ◽  
Mature Size

Defining the age of attainment of physical maturity is important for many studies, including identification of stocks, populations or species. In order to identify the age when the skull of the bottlenose dolphin, Tursiops truncatus, reaches maturity, skulls of fifty-three specimens found stranded along the coasts of southern Brazil, Uruguay and northern Argentina (27o35’S, 48o34’W-36o49’S, 55o19’W) were analyzed. Sixty skull measurements were taken to compare the growth rate of the different functional apparatuses. Age was estimated by counts of growth layer groups in the dentine of decalcified, stained longitudinal sections of teeth. Von Bertalanffy’s equation was applied to assess the growth and determine the age at maturity of each apparatus. Generally the maturation of skull starts at age two and stabilizes at age five, and the age of reaching the mature size varies amongst different characters. The braincase is the most precocious apparatus, while the feeding is the one that last stabilizes. The development patterns observed for the hearing, vision and breathing apparatuses were similar. Statistic analysis revealed significant differences among the ages at maturity, but not for von Bertalanffy’s growth equation parameters for each functional apparatus. For the studied population it is suggested that skulls can be considered mature in animals with more than five years. 

COUNTS OF GROWTH LAYER GROUPS IN CEMENTUM AND DENTINE IN RINGED SEALS (PHOCA HISPIDA)

1996 ◽  
Vol 12 (3) ◽  
pp. 383-401 ◽  
Author(s):  
Robert E. A. Stewart ◽  
Barbara E. Stewart ◽  
Ian Stirling ◽  
Elaine Street
Keyword(s):  
Growth Layer ◽  
Phoca Hispida ◽  
Ringed Seals ◽  
Layer Groups

scholarly journals Mixed odontogenic tumors in four young dogs: ameloblastic fibroma and ameloblastic fibro-odontoma

2018 ◽  
Vol 31 (1) ◽  
pp. 98-102 ◽  
Author(s):  
Patrick Huang ◽  
Cynthia Bell ◽  
Vanessa Wallace ◽  
Brian G. Murphy
Keyword(s):  
Dental Pulp ◽  
Tooth Development ◽  
Odontogenic Tumors ◽  
Diagnostic Features ◽  
Early Stages ◽  
Odontogenic Epithelium ◽  
Ameloblastic Fibroma ◽  
Mixed Odontogenic Tumors

Ameloblastic fibroma (AF) and ameloblastic fibro-odontoma (AFO) are mixed odontogenic tumors (odontogenic tumors with induction) that are reported only rarely in dogs. These tumors are histologically complex and, to a degree, recapitulate the early stages of tooth development, comprising 2 types of tissue: neoplastic odontogenic epithelium, and induced ectomesenchyme (dental pulp). AFOs are distinguished from AFs by the additional presence of hard dental matrices such as dentin. Herein, we describe the key diagnostic features of AF and AFO in 4 young dogs.

scholarly journals Methodological and applied aspects of classification and typology of international geopolitical conflicts

2020 ◽  
pp. 38-53
Author(s):  
Aleksandr Aleksandrovich Tikhov
Keyword(s):  
Integral Approach ◽  
Modern World ◽  
Key Factors ◽  
Diagnostic Features ◽  
Geographical Environment ◽  
The Matrix ◽  
Conflict Interaction ◽  
Qualitative Changes

This article is dedicated to the development of methods and applied aspects of the typology of international geopolitical conflicts in modern world. Relevance of this topic is substantiated by intensification of intergovernmental conflicts on the regional and transregional levels, as well as escalation of sociopolitical tension. The author offers a method of classification of geopolitical conflicts that considers spatial and time specificity of such forms of cooperation and is based on the comprehensive analysis of all components of the process. As one of the key factors, the author highlights the causes and prerequisites for formation of a conflict. An integral approach towards typology of the forms of conflict interaction between the countries is being developed on the basis of three-way classification matrix. The matrix is based on the three diagnostic features that characterize the key factors of formation and development of a conflict, and substantiate a subsequent model of intensification of a conflict. This allows achieving the necessary level of objectivity for conducting further complex diagnostics of geopolitical conflict and precision of the result of typology using the instruments and methodology of different scientific approaches towards studying such type of processes. The proposed method may be used in studying certain types of geopolitical conflicts of the past and present, forecasting the development and qualitative changes of a certain conflict in future, as well as comprehensive assessment of conflict potential of a particular territory of region as a whole. In the course of this work, the author established and confirmed interpretation and interdependence between the political decisions of one or another country and the corresponding geographical environment. Determination of causal lings allow viewing the method as a foundation for future examination of conflicts and forecast their development.

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