Micro-CT Imaging Techniques for Visualising Pinniped Mystacial Pad Musculature

Pinnipeds, including seals, sea lions and walruses, heavily rely on their vibrissae (whiskers), for foraging, hunting and navigation. Despite their specialised vibrissae anatomy, comprehensive descriptions of vibrissae musculature remain scarce. The three-dimensional curved structure of pinniped mystacial pad presents challenges when describing their vibrissal musculature, vital for understanding the relationship between muscle morphology and sensory control in pinnipeds. Traditional histology methods offer limited and potentially distorted insights due to their two-dimensional nature, necessitating alternative imaging approaches. Advanced imaging techniques, like X-ray computed tomography (CT), have revolutionised our understanding of anatomical structures, particularly in evolutionary biology and comparative anatomy. Employing micro-CT and diceCT to provide detailed visualisations of musculature of mystacial pads in harbour seals (Phoca vitulina), our objectives include optimising scanning methodology and establishing repeatable data analysis workflow. Optimisation involved adjusting scan parameters such as X-ray voltage, power, filtering settings and staining conditions, while workflow development encompasses testing diverse data filtering and segmentation methods, including automated, semi-automated and manual segmentation combinations. While solely conducted in Avizo-Amira, principles are applicable to other image processing packages. Stained mystacial pads yielded clearer visualizations of the vibrissae musculature, enhancing insights into their intricate muscle morphology. Despite challenges, micro-CT proves invaluable for understanding sensory anatomy in pinnipeds. diceCT could therefore contribute significantly to pinniped musculature research, providing a comprehensive understanding of their sensory systems. This study significantly advances our ability to determine pinniped anatomy through imaging technologies. Accurate identification of musculature is crucial, unraveling sensory anatomy in pinnipeds, emphasizing the importance for refining methodologies for future research.