Three-dimensional morphology of the vibrissal array of the harbor seal (Phoca vitulina)

Abstract

AbstractNearly all mammals have specialized facial hairs known as vibrissae (whiskers) that serve a variety of functions, including tactile exploration and flow sensing. The geometric arrangement of the whiskers on an animal’s face as well as each whisker’s individual geometry will play a critical role in determining the sensory information that the animal acquires. To date, however, the relationships between vibrissal morphology and functional use remain largely unexplored. In the present work, we quantify the three-dimensional morphology of the vibrissal array of the harbor seal (Phoca vitulina). Specifically, we develop relationships between a whisker’s basepoint location and its arc length, its intrinsic curvature, and the angles at which it emerges from the mystacial pad. Results show that the arc length of seal whisker ranges between 20 – 120 mm, and the shape of a seal whisker is well-described by a cubic equation. The orientation at which each whisker emerges from the seal’s face can be described by three angles. The angle of emergence in the horizontal plane depends on both the whisker’s dorsal-ventral as well as its rostral-caudal basepoint location. In contrast, the angle of emergence in the elevation plane depends only on the whisker’s dorsal-ventral basepoint location. Finally, the angle that the whisker “twists” about its own axis again depends on both dorsal-ventral and rostral-caudal basepoint location. We discuss how the morphology of the array could create a range of mechanical responses specialized for tactile or flow sensing.SUMMARY STATEMENTWe quantify the three-dimensional position and orientation of the whiskers across the face of the harbor seal and discuss how this geometrical arrangement could aid in flow sensing and touch.