Evolutionary and comparative anatomical investigations of the autonomic cardiac nervous system in the African...

The purpose of this study was to clarify the general architecture and morphological variations of the autonomic cardiac nervous system (ACNS) in the African Cercopithecidae (Old World monkeys), and to discuss the evolutionary changes between this system in African/Asian Cercopithecidae and humans. A detailed macroscopic comparative morphological investigation of the ACNS was performed by examining the left and right sides of 11 African cercopithecid specimens, including some previously unreported species (Abyssinian colobus, Angola pied colobus, Savanna monkey, and lesser white-nosed guenon). The common characteristics of the ACNS in the African Cercopithecidae are described in detail. Consequently, homologies of the ACNS between Asian (macaques) and African Cercopithecidae, and differences between the Asian/African Cercopithecidae and humans, were found. In particular, differences in the sympathetic (cardiac) systems of the Cercopithecidae and humans were recognized, despite the similar morphology of the parasympathetic vagal (cardiac) system. These differences include the composition of the cervicothoracic ganglion, the lower positions of the middle cervical and cervicothoracic ganglia, and the narrow range for the origin of the cardiac nerves in the Cercopithecidae, compared with that in humans. In conclusion, these findings are considered with regard to the morphology of the last common ancestors of the Cercopithecidae.