Untersuchungen zur Schädel- und Gebisspathologie bei Seehunden (Phoca vitulina) und Kegelrobben (Halichoerus grypus) sowie zur altersabhängigen Veränderung von Knochendichte und Mikroarchitektur im Seehund-Unterkiefer

• Main Author: Kahle, Patricia
• Format: Doctoral or Postdoctoral Thesis
• Language: German
• Published: 2019
• Subjects: ddc:570; harbor seal; Phoca vitulina; seehund
• Online Access: https://hildok.bsz-bw.de/frontdoor/index/index/docId/1090; https://nbn-resolving.org/urn:nbn:de:gbv:hil2-opus4-10900; https://doi.org/10.25528/034; https://hildok.bsz-bw.de/files/1090/Dissertation_Kahle_2019.pdf

Skulls of 1,901 harbor seals from the North Sea were systematically investigated for dental, periodontal and cranial disorders as well as pathological changes of the temporomandibular joint (TMJ). Volumetric bone mineral density (vBMD) and microarchitecture of the mandible of a subsample of these specimens were analyzed in respect to age-related changes. Age at death of examined seals ranged from 1 week to 25 years. Most of the specimens were collected in 1988, when the population suffered from a phocine distemper virus epizootic. Therefore, it is assumed that, contrary to other museum collections, only little overrepresentation of pathological skeletal condition is present in the analyzed death sample. Age- and sex-related differences in the frequency and severity of pathological changes were observed in the dentition and the TMJ. Intravital tooth loss, tooth fracture and periapical lesions were recorded more frequently in male seals than in femals. Lesions consistent with temporomandibular joint osteoarthritis (TMJ-OA) also occurred more frequently in males, while lesion severity tended to be higher in female specimens. Severity of TMJ-OA lesions was positively correlated with age. Significant age-related changes in vBMD and several microarchitectural parameters were observed between individuals of the age classes “young juveniles” (0.5–10 months),“yearlings” (12–23 months),and “adults” (12–25 years),indicating an overall increase in cortical and trabecular area, cortical thickness as well as vBMD with age. For juvenile animals (≤ 23 months), positive correlations with age were observed for cortical area and thickness, trabecular separation, as well as vBMD. Negative correlations with age existed for trabecular number and thickness as well as for trabecular bone volume fraction (BV/TV) in the juveniles. The findings suggest a reduction in BV/TV with age,due to the bone trabeculae becoming thinner,less numerous and more widely spaced. This detailed knowledge of age-related changes in the structure and mineralization of bones is an important prerequisite for interpreting osseous changes in wild mammals caused by external factors, as such as exposure to environmental contaminants. The examination of large skeletal collections enables the observation also of rare pathological conditions. In the present investigation a case of anodontia,diagnosed as a manifestation of hypohidrotic ectodermal dysplasia was for the first time described in the harbor seal. In five juvenile Baltic grey seals,severe osteomyelitis of the jaws was described for the first time. The condition was attributed to disturbed dentin formation,presumably of genetic causation, in the affected individuals. The present study highlights the fact that systematic analyses of museum collections can provide important insights into the dental and skeletal pathology of wild mammals. These data can be used for reconstructing the health situation and living condition of past animal population.