3D Anatomy of the Jaw Muscles of the Spiny‐Tailed Dogfish ( Squalus acanthius )

Abstract

New technologies are enabling anatomists to see inside animals to better understand the organization and function of the musculoskeletal system. Among the great transformations in vertebrate evolution is the acquisition and diversification of jaws and jaw musculature. Sharks are key species used in anatomy courses as well as research in organismal evolutionary biology where there is considerable diversity in cranial function and feeding behavior in the clade. Here, we use contrast imaging and 3D muscle fiber architecture visualization approaches to model and demonstrate the jaws and jaw muscles of the spinytailed dogfish (Sqaulus acanthius). A specimen was microCTed following immersion in an iodine-ethanol solution. Muscles and cartilages were segmented using Avizo. Muscle fascicles were then modeled using automated methods followed by manual noise reduction approaches. Colors of modeled fascicles were modeled to reflect orientations of muscles to reveal qualitative patterns in fiber organization. These segmented models of fascicles were then projected in quantitative space to show the orientations of muscle fascicles and moments of the quadratomandibularis, preorbitalis and levator hyomandibulae muscles among others. This 3D model will be shared with educators to include in comparative vertebrate anatomy courses. The results from the muscle architecture and mechanics data will be used to compare with other fishes and tetrapods as part of a growing study on the evolution of jaw muscles in vertebrates.