Segmental composition and nerve distribution of the brachial plexus in Galictis cuja

Galictis cuja is a neotropical mustelid with terrestrial locomotor habits, yet the anatomy of its brachial plexus has remained undescribed. This study characterizes the origin, organization, and distribution of the brachial plexus nerves in 15 adult specimens (30 antimeres). Dissections revealed a consistently compact plexus formed by the ventral branches of the cervical and thoracic spinal nerves (C6-T1), with high bilateral symmetry and predominance of plurisegmental nerves. Segmental contributions were uneven, with C7 representing the most frequent contributor, followed by C6, C8, and T1. Principal component analysis demonstrated a clear craniocaudal modular organization of the plexus, separating a cranial group of nerves associated with scapular stabilization and proximal limb control (dominated by C6-C7) from a caudal group supplying the more distal intrinsic muscles (dominated by C8-T1). The first two principal components accounted for 91.97% of the total variance, with PC1 reflecting a strong craniocaudal gradient in segmental input. Compared with other mustelids, G. cuja showed a C6-T1 configuration, differing from species in which the plexus extends caudally to T2, while still exhibiting pronounced internal modularity. These findings provide a comprehensive description of the brachial plexus in G. cuja, contribute to comparative interpretations of mustelid forelimb innervation, and offer an anatomical basis for clinical and experimental applications involving wild carnivorans.