52 - Cats vs. Dogs: Exploring the Evolutionary Divergence of Facial Muscles in Wild Felids and Canids

Poster Board Number: 52
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Co-authors:

Anne Burrows, Ph.D. - Professor, Physical Therapy, Duquesne University; Sarah Downing, B.S. - Lab Manager, Physical Therapy, Duquesne University

Abstract Body : Prior research has established that the facial musculature of the gray wolf, a wild canid, predominantly clusters around the ear and oral regions. These social mammals exhibit an extensive repertoire of facial expressions using these muscles and are characterized by their long-distance vocalizations that specifically exercise the musculature surrounding the upper and lower lip regions. In contrast, our current knowledge of the facial musculature in wild felids is less understood and lacking in defined region(s) of divergence. The current study aims to enhance our insight of wild felid facial musculature by performing facial dissections on several felid species including the tiger (Panthera tigris), the Amur leopard (Panthera pardus), the cougar (Puma concolor,) and caracal (Caracal caracal), and comparing these findings with those in the gray wolf. We hypothesized that wild felid facial muscles would primarily cluster in the ear region because these species are nocturnal and more solitary than the wolf. Additionally, we expected immunohistochemical techniques to reveal mostly fast-twitch muscle fibers in the wild felid face, as most mammals have shown a majority of fast-twitch fibers in facial muscles. Dissections were performed with traditional tools. A midline incision was made in each face starting at the dorsal cervical region and passing through the occipital, frontal, nasal, and oral regions to uncover the facial musculature. The resulting facial ‘masks’ were set aside to dry before connective tissue and fascia were removed. Gross dissections revealed a similar but less abundant repertoire of facial musculature in the ocular, nasal, and oral regions of the felids as found in the wolves, with many of the muscles clustered around the ear regions. Histological samples were taken from the ear regions of each species and immunohistochemistry was used to identify fast and slow-twitch myosin fibers. Unexpectedly, about 50% of the fibers were fast-reacting and 50% were slow-reacting. These results reflect the divergence in the evolutionary ecology of felids and canids, and correlate with their social behavior.