Do Innervation Patterns of Mystacial Vibrissae in Harbor Seals, Phoca Vitulina, Explain Specialization in Trail Following Behavior?

• Main Author: Jones, Aubree Elizabeth
• Other Authors: Marshall, Christopher
• Format: Thesis
• Language: unknown
• Published: 2019
• Subjects: Vibrissae; whiskers; pinniped sensory systems; foraging; Erignathus barbatus; harbor seal; Phoca vitulina
• Online Access: https://hdl.handle.net/1969.1/177572

The microstructure of vibrissae, or whiskers, of terrestrial mammals has been well-studied, but the study of marine mammal vibrissae is relatively overlooked. The lack of comparative data regarding the vibrissae, or follicle-sinus complex (F-SC) of marine mammals has hampered the ability to answer questions about the function and evolution of these sensory structures. Harbor seals, Phoca vitulina, are a well-studied pinniped species with readily available data regarding their feeding ecology and prey tracking behavior using vibrissae. This latter behavior termed “hydrodynamic trail following” behavior is well documented. To best understand the functional use of harbor seal vibrissae, however, the microstructure and innervation patterns need to be understood to compare harbor seals to phocids for which neurological data is already available. To close this gap in the phocid dataset, the largest F-SCs from five individuals were processed histologically. Axon counts were obtained to study innervation investment, while morphometric data was collected to study the microstructure of F-SCs. Harbor seal vibrissae had similar axon counts/F-SC and microstructure to other phocid species. Axon counts were converted to densities in the lateral columns of vibrissae, to correct for size, and compared to harp seals. The lateral vibrissae of harbor seals had more axons per mm2 than harp seals, which accounts for the harbor seals specialization for trail following. Whether this difference in is typical for phocids needs to be better understood by comparing innervation investment to other pinnipeds, such as otariids, and phocid species that diverge from the phocid pattern, like bearded seals (Erignathus barbatus).