The vomeronasal organ of New World monkeys (platyrrhini)

Although all platyrrhine primates possess a vomeronasal organ (VNO), few species have been studied in detail. Here, we revisit the microanatomy of the VNO and related features in serially sectioned samples from 41 platyrrhine cadavers (14 species) of mixed age. Procedures to identify terminally differentiated vomeronasal sensory neurons (VSNs) via immunolabeling of olfactory marker protein (OMP) were used on selected specimens. The VNO varies from an elongated epithelial tube (e.g., Ateles fusciceps) to a dorsoventrally expanded sac (e.g., Saguinus spp.). The cartilage that surrounds the VNO is J-shaped or U-shaped in most species, and articulates with a groove on the bony palate. Preliminary results indicate a significant correlation between the length of this groove and length of the VNO neuroepithelium, indicating this feature may serve as a skeletal correlate. The VNO neuroepithelium could be identified in all adult primates except Alouatta, in which poor preservation prevented determination. The VNO of Ateles, described in detail for the first time, had several rows of VSNs and nerves in the surrounding lamina propria. Patterns of OMP-reactivity in the VNO of perinatal platyrrhines indicate that few or no terminally differentiated VSNs are present at birth, thus supporting the hypothesis that some platyrrhines may have delayed maturation of the VNO. From a functional perspective, all platyrrhines studied possess structures required for chemoreception (VSNs, vomeronasal nerves). However, some microanatomical findings, such as limited reactivity to OMP in some species, indicate that some lineages of New World monkeys may have a reduced or vestigial vomeronasal system.

Light microscopic and ultrastructural observations on the vomeronasal organ of Anoura (Chiroptera: Phyllostomidae)

The vomeronasal organ (VNO) is known to be present in bats of the family Phyllostomidae, but in most species this is inferred from the presence of accessory olfactory bulbs. Like primates, bats have profound intergroup variations in the vomeronasal system. Of the family Phyllostomidae (49 genera, 143 species) the VNO of approximately 60 species has been studied. Here, we report light microscopic observations of the VNO of Anoura geoffroyi (fetus and adult), A. caudifer, and A. cultrata, as well as ultrastructural observations of the VNO in adult A. geoffroyi. The organ is crescent-shaped, with a wide lumen encroached by a "mushroom body" that contains a venous sinus. In adults, the vomeronasal cartilage is reduced, being longer in absolute length in fetal A. geoffroyi compared with the adult. In the neuroepithelium, the receptor cell microvilli are dark, distinct, and short, emerging from a vesicular tuft; the supporting cell microvilli are relatively much longer. Large paravomeronasal ganglia are observed. The receptor-free epithelium is undulating and lacks cilia or microvilli. Some characteristics of the VNO in Anoura have not been reported in other chiropterans to date, such as the marked reduction of the vomeronasal cartilage and absence of cilia in the receptor-free epithelium. Moreover, if A. geoffroyi is representative, the genus has an adult neuroepithelial volume similar to other mammals of its body size. Further examination of uninvestigated phyllostomid VNOs may elucidate a phylogenetic history of the family, as well as ecological or social correlates of the VNO in the order Chiroptera.