Summary
The marginal epithelium of the lateral auricles of the planarian, Dugesia tigrina, includes a cell type with surface cilia and microvilli, a basal nucleus, and dense cytoplasm containing secretory vacuoles, Golgi elements, mitochondria and ribosomes. Through channels within the epithelial cytoplasm, cellular processes, interpreted as extensions of neurosensory receptor cells located in the subepidermis, project to the surface. The receptor processes, containing microtubules, mitochondria, vesicles and an agranular tubular reticulum, project beyond the epithelial cell surface; one or two cilia each emerge from a basal body in the apex of the projection. Close to the point of emergence to the epithelial surface, each cylindrical receptor process is surrounded by a collar-like septate junction between adjacent plasma membranes. The cilia of the projections differ from those of the epithelial cells in diameter, density of matrix and in the banding patterns of the rootlets. A few projections appear with the apex and basal body retracted below the epithelial surface. The possible function of these ciliated processes in sensory reception is discussed.
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To Professor Arthur Wagg Pollister, I respectfully dedicate this article on the occasion of his retirement from Columbia University.
This work was supported by Grant No. SO 1 FR 5369 from the U.S. Public Health Service to the University of Illinois at the Medical Center.
I thank Dr. J. P. Marbarger, Director of the Research Resources Laboratory, for use of the electron microscope facilities, Miss Irena Kairys for technical help, Miss Marie Jaeger for assistance with photography, and Mr. Robert Parshall for the drawing.
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MacRae, E.K. The fine structure of sensory receptor processes in the auricular epithelium of the planarian, Dugesia tigrina . Z. Zellforsch. 82, 479–494 (1967). https://doi.org/10.1007/BF00337119
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DOI: https://doi.org/10.1007/BF00337119