Olfactory epithelium of Necturus maculosus and Ambystoma tigrinum.

The morphological study presented here provides a general description of the elements of the olfactory epithelium in the mud puppy and tiger salamander,, and gives evidence about their dynamic activity and interrelationships. There are morphological indications of local bursts of reduplication and a continual line of differentiation of receptor cells from basal cell progenitors through stages of mature development to senescence (indicated by the accumulation of pigment granules) and cell death and disposal (by expulsion of pycnotic cell nuclei and by phagocytosis by macrophages). The supporting cells probably play several roles: a secretory role which supplements the activity of Bowman's glands, a minor insulating role in which some dendrites are shielded from the surrounding milieu, and a skeletal role in which they facilitate the efficient displacement of dendrites. The dendrites are regularly arranged in organized relationships with one another and are for the most part in direct apposition, separated only by a 200 A intercellular gap, thus suggesting the possibility of functional interrelationships. This study emphasizes the fact that efficient planning of experimental investigations must include knowledge and consideration of the thickness of the particular olfactory epithelium under study. It also suggests that because of the large receptor-cell size, the mud puppy and/or tiger salamander would make good model systems for single cell recording. Further, the olfactory epithelia of these species are suggested as favorable targets for studies of the aging process in nerve cells.