Browsing by Author "Doubell, Narusa Suria"

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    The comparative functional anatomy of the forelimb in two african mole-rat species, bathyergus suillus and heterocephalus glaber.
    (Stellenbosch : Stellenbosch University, 2021-12) Doubell, Narusa Suria; Kotzé, Sanet H.; Sahd, Lauren; Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Biomedical Sciences. Anatomy and Histology. Division of Clinical Anatomy.
    ENGLISH ABSTRACT: Different digging and communication methods are observed in various subterranean mole-rat species. Seismic signalling in the form of hind foot-drumming is the main communication method in most solitary mole-rat species, such as the scratch-digging Bathyergus suillus. The aim of the present study was to determine if hind foot-drumming and scratch-digging influence the morphology of the fore limb muscles in a drumming, scratch-digging species, B. suillus, belonging to the family Bathyergidae and a non-drumming, chisel-tooth digging species, Heterocephalus glaber belonging to the family Heterocephalidae. Furthermore, the secondary aim was to determine if somatosensory mechanisms that may be responsible for the detection of seismic signals could be identified histologically in the foot pads and lateral aspect of the feet in both species. Four muscle architecture parameters were measured and compared in 40 formalin-fixed muscles from the right forelimb of each species (n=6). The composition of type I and II fibres as well as the glycolytic, oxidative glycolytic and oxidative fibres in 21 forelimb muscles were histochemically and immunohistochemically determined in six fresh B. suillus and six fixed H. glaber specimens. The densities of Pacinian corpuscles, Merkel cells, Ruffini corpuscles and Meissner corpuscles were determined within the footpads and the morphology of the robust hairs on the lateral aspect of the feet was described. Muscles involved in the power stroke of digging had higher muscle mass percentage, force output and shortening capacity in B. suillus compared to H. glaber. Significantly higher percentages of glycolytic fibres were observed in the scapular elevators and digital flexors of B. suillus. These results suggest that the forelimb muscles involved in digging in B. suillus provide fast and powerful motions for effective burrowing. The m. sternohyoideus had significantly more oxidative fibres in H. glaber compared to B. suillus. Furthermore, the m. sternocleidomastoideus in H. glaber had significantly higher physiological cross-sectional area (PCSA) and fascicle length values compared to B. suillus. Regionalisation of type I and II fibres was observed in the m. claviculo-scapularis of B. suillus and m. triceps brachii caput medialis in H. glaber. Significantly higher densities of Meissner corpuscles in the drumming B. suillus suggests that this somatosensory mechanism in their footpads may be responsible for detecting seismic signals. The hairs on the lateral aspect of the feet did not have the typical follicle-sinus complex seen in sensory hairs. However, Merkel cells within the outer root sheath and the nervous tissue surrounding the hairs in both species are indicative of functioning either as tactile perception for movement in burrows or moving loosened soil around within the burrows. Stellenbosch University https://scholar.sun.ac.za iv In conclusion, the differences in the muscle architecture and muscle fibre typing between the two species may reflect adaptations for scratch-digging and production of seismic signals in B. suillus. Additionally, the muscle architecture and fibre type compositions in the neck muscles of H. glaber may point toward faster contractions for chisel-tooth digging. However, the phylogeny of the two species may also be responsible for these differences and not just behavioural demands such as hind foot-drumming and digging methods.