Doctoral Degrees (Anatomy and Histology)

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Browsing Doctoral Degrees (Anatomy and Histology) by browse.metadata.advisor "Bennett, Nigel C."

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    The anatomy of seismic signalling: morphological adaptations of the hind limb in drumming and non-drumming African mole-rats (Bathyergidae)
    (Stellenbosch : Stellenbosch University, 2021., 2021-03-31) Sahd, Lauren; Kotze, Sanet H.; Bennett, Nigel C.; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Anatomy and Histology.
    ENGLISH ABSTRACT: Hind foot drumming is one of the most common forms of seismic signalling. The family Bathyergidae (African mole-rats) is well known for exhibiting hind foot drumming during courtship and territorial behaviour. Hind foot drumming in bathyergid species arises as a result of the rapid flexion and extension of the hip and knee joints by either a single or alternating hind limbs. While the ecological context of drumming in these species has been well described, the possible morphological adaptations to enable the production of these seismic signals, have yet to be unravelled. Therefore, the primary aim of the present study was to investigate if morphologically discernible adaptations to the hind limb osteology and muscles could be determined in two drumming (Georychus capensis and Bathyergus suillus) and one non-drumming species (Cryptomys hottentotus natalensis) of African mole-rats using a variety of techniques. The gross anatomy of the hind limb was investigated by undertaking detailed dissections to determine the origin and insertion points as well as the innervation of the muscles of the hind limb. Thereafter, 32 muscles were removed from a single limb (with joint angles closest to 90°) for muscle architecture measurements which included belly length, muscle fascicle length, muscle mass and physiological cross-sectional area. The remaining soft tissue was removed from the specimens by maceration to enable the description of the osteology of the hind limb. Additionally, morpho-functional indices were used to morphometrically compare the bones between species. Twenty-one hind limb muscles were selected to undergo muscle fibre typing using myosin heavy chain slow antibody immunohistochemical staining. The amount of positive fibres was quantified to determine the total percentage of slow muscle fibres in each muscle section. Micro computed tomography (CT) scans of contrast enhanced stained specimens were used to determine accurate volumetric measurements of 26 muscles per sample in all three species as well as to assemble three dimensional reconstructions of the musculature of the limbs. Musculus gracilis anticus may play a key role in hind foot drumming as it was the only muscle that was morphologically different between the drummers and non-drummer. In the two drumming species, m. gracilis was a single muscle, whereas it was double in C. h. natalensis. Additionally, it was the only muscle to be significantly different in G. capensis and C. h. natalensis for all muscle architecture parameters analysed. Furthermore, m. gracilis anticus was the only muscle that had a significant difference in the volume as determined by the micro CT scans between the two drumming species and C. h. natalensis. However, the number of slow fibres of m. gracilis anticus was not significantly different between G. capensis and C. h. natalensis. Furthermore, the robust tibias in the drumming species, as indicated by the tibial robustness index, possibly counter the additional biomechanical load caused by the muscles (specifically m. gracilis anticus) involved with hind foot drumming. Thus, it can be concluded that there are distinct morphological adaptations to the osteology and musculature of the two hind foot drumming species.