Reappraisal of the vomeronasal system of catarrhine primates: Ontogeny, morphology, functionality, and persisting questions

The vomeronasal organ (VNO) is a chemosensory organ that functions in socio sexual communication in many vertebrates. In strepsirhine primates and New World monkeys, the bilateral VNOs are traditionally understood to exist as a well-developed chemosensory epithelial unit. In contrast, the VNOs of cat arrhine primates are thought to be absent or exist only as reduced epitheli al tubes of uncertain function. However, the VNO of New World monkeys shows substantial variation in the extent of sensory epithelium. Recent findings that the chimpanzee (Pan troglodytes) possesses a VNO similar to humans su ggest the variability of the VNO among haplorhine primates may be more exte nsive than previously thought, and perhaps more at par with that observed i n chiropterans. The atypical histologic structure and location of the human /chimpanzee VNO suggest accessory glandular secretion and transport functio ns. Other catarrhine primates (e.g., Macaca spp.), may truly be characteriz ed by VNO absence. Unique aspects of facial growth and development in catar rhine primates may influence the position or even presence of the VNO in ad ults. These recent findings demonstrate that previous investigations on som e catarrhine primates may have missed the VNO and underestimated the extent of variability. As an understanding of this variation increases, our view of VNO functionality and associated terminology is changing. Further invest igations are needed to consider phylogenetic implications of VNO variabilit y and the association of craniofacial form and VNO anatomic position in pri mates. Anat Rec (New Anat) 265:176-192, 2001. (C) 2001 Wiley-Liss, Inc.