Comparative anatomy and evolution of the cardiac innervation in New World monkeys (Platyrrhini, e. Geoffroy, 1812)

Abstract

The morphology of the autonomic cardiac nervous system (ACNS) was examined in 24 sides of 12 New World monkeys (Platyrrhini) of all four families to document the morphology systematically and to study the evolutionary changes of the ACNS in this primate lineage. We report the following: (1) Although several trivial intra- and inter-specific variations are present, a family-dependent morphology of the ACNS does not exist in New World monkeys. (2) The sympathetic ganglia in New World monkeys consist of the superior cervical, the middle cervical, and the cervicothoracic which is composed of the inferior cervical and first and second thoracic, and the thoracic ganglia starting with the third thoracic. The general cardiac nervous system is the sympathetic middle and inferior cardiac nerves and all parasympathetic vagal cardiac branches. (3) The morphology of the ACNS in the New World monkeys is almost consistent regardless of the number of vertebrae, the cardiac position and deviation (axis), and the great arterial branching pattern of the aortic arch, and it is very similar to that in the Old World monkeys, with only one difference: the superior cervical ganglion in the New World monkeys tends to be relatively smaller, higher, and provides a narrower contribution to the spinal nerves than in the Old World monkeys. The ACNS morphology exhibits significant evolutionary changes within the primate lineage from New and Old World monkeys to humans. The comparative morphology within the lineage is concordant with the phylogeny, suggesting that the primate ACNS preserves its evolutionary history in close alignment with phylogeny.