Innervation Patterns of Harp Seal (Pagophilus groenlandicus) Vibrissal Sensory Systems

The study investigated the innervation and microanatomy of harp seal vibrissal Follicle-Sinus Complexes (F-SCs), revealing that harp seals had 88-105 F-SCs with a tripartite blood organization system. Medial F-SCs had more symmetrical dermal capsule thicknesses and fewer axons compared to lateral F-SCs, which had higher axon counts, averaging 1221 axons/F-SC. The study found that conventional analyses overestimated innervation by about 10-20% due to focusing only on lateral vibrissae. The relationship between axon count and F-SC surface area was non-linear, and axon densities were consistent across the snout. The findings supported the idea of functional compartmentalization between medial and lateral vibrissae and suggested that vibrissal innervation variation among mammals diverged due to phylogeny and environmental factors.