OLFACTORY MUCOSA OF THE SOUTH-AMERICAN ARMADILLO CHAETOPHRACTUS-VILLOSUS - AN ULTRASTRUCTURAL-STUDY

The sense of olfaction in armadillos plays an important role, suggeste d by the great development of the nasal structures, olfactory bulbs, a nd related brain regions. The mammalian olfactory mucosa is a privileg ed site of neuronal death and regeneration during the whole Life span. A detailed knowledge of its ultrastructure is convenient for gaining insight into the factors controlling those phenomena. We performed thi s work in species not previously studied in order to provide a firm ba sis for further research on those factors. No information is available on the histology and ultrastructure of the olfactory mucosa in the or der Xenarthra to which armadillos belong. Samples from the endoturbina ls of the armadillo Chaetophractus villosus were prepared for Light an d electron microscopic examination by the usual conventional means. Th e olfactory epithelium of Chaetophractus villosus shows the classical three types of cells: supporting cells, olfactory receptor neurons, an d basal cells. The olfactory neurons and the basal cells were similar to that described in other species. Two different types of supporting cells are described. An outstanding characteristic of the supporting c ells is the normal presence of abundant phagosomes, apical secretory g ranules, apocrine-like protrusions, and highly developed smooth endopl asmic reticulum. Apoptotic bodies are frequently found in the infranuc lear cytoplasm of supporting cells. The ductular epithelium of Bowman' s glands reveals secretory activity. The lamina propria shows mixed Bo wman's glands. Great development of smooth endoplasmic reticulum is ob served in the mucous acinar cells. Evidence for merocrine and apocrine mechanisms in the Bowman's glands is presented. The presence of apopt otic bodies and phagosomes in supporting cells suggests a participatio n in the cellular events induced by cell death and proliferation of th e olfactory epithelium. The variety of characteristics exhibited by th e supporting cells of the olfactory mucosa may contribute to a deeper understanding of their scarcely known functions. Anat. Rec. 252: 325-3 39, 1998. (C) 1998 Wiley-Liss, Inc.