# Anatomical Behaviour of the Phrenic Nerve and Innervation of the Diaphragm in the Maned Wolf ( Chrysocyon brachyurus )

## TL;DR

This study describes the phrenic nerve anatomy and diaphragm innervation in maned wolves, revealing unique features compared to other carnivores.

## Contribution

The study provides the first detailed anatomical description of the phrenic nerve in the maned wolf.

## Key findings

- The phrenic nerve in maned wolves originates from the ventral branches of C5, C6, and C7.
- The nerve splits into the lumbocostal trunk and sternal branch, with no innervation of the central tendon or caudal vena cava.
- The findings show similarities to the crab-eating fox but significant differences from the domestic dog.

## Abstract

The phrenic nerve is responsible for the motor innervation of the diaphragm, which is essential for breathing. The literature lacks data regarding the nervous and respiratory systems of wild animals, especially the maned wolf (
Chrysocyon brachyurus
). Therefore, this study aimed to describe the origin and terminal distribution of the phrenic nerve in the diaphragm of
Chrysocyon brachyurus
. Seven maned wolf specimens were preserved by a 10% formaldehyde solution and were later dissected. The phrenic nerve most frequently originated from the ventral branches of C5, C6, and C7, forming trunks that merged when they reached the first rib. Upon the diaphragm, the phrenic nerve exhibited a terminal bifurcation into the lumbocostal trunk and the sternal branch. The distribution of the branches was symmetrical and specific to the lumbar, costal, and sternal portions of the diaphragm, with no innervation of the central tendon or caudal vena cava. It was not observed contributions from the intercostal nerves to the diaphragm innervation. It is concluded that the phrenic nerve of the maned wolf originates from the ventral branches of C5, C6, and C7, showing unisegmental or plurisegmental characteristics and representing the sole nervous supply to the diaphragm in this species. The findings demonstrate similarities with what is described in the crab‐eating fox, but there are significant differences compared to the domestic dog, indicating interspecies variability in phrenic nerve morphology among carnivores and highlighting the need for further comparative studies.