Ultrastructure of the osphradium of Aplysia californica |
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Authors: | J -M Theier V F Castellucci Dr A J Baertschi |
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Institution: | (1) Department of Physiology, University of Virginia, School of Medicine, Charlottesville, Virginia, USA;(2) Columbia University, New York, USA;(3) Department of Physiology, School of Medicine, University of Virginia, Jordan Hall, Box 449, 22908 Charlottesville, VA, USA |
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Abstract: | Summary The osphradium of Aplysia californica, a sensory organ, is a small yellow-brown epithelial patch located in the mantle cavity immediately anterior to the rostral attachment of the gill. Scanning electron microscopy reveals a round ellipsoid structure of 0.6–1 mm in diameter with a central, occasionally folded, sensory epithelium. The central area is covered with microvilli and surrounded by a densely ciliated epithelium. Transmission electron micrographs show that the columnar supporting cells in the sensory epithelium contain an abundance of apical pigment granules and microvilli. Between the epithelial-supporting cells, the putative sensory elements consist of thin neurites (0.4–1.5 m in diameter) that reach the sea-water side of the osphradium. The neurites contain many neurotubules, mitochondria, vesicles and cilia in their apices. The nerve endings originate from cell bodies up to 40 m below the epithelium or in the osphradial ganglion itself, as revealed by electron microscopy and retrograde labeling with Lucifer yellow. There appear to be two populations of putative sensory cells, a large population of heavily stained cell bodies 4–10 m in diameter and a few scattered cells of large diameter (25–60 m). Following lanthanum impregnation, septate junctions can be seen between all types of cells in the epithelium, 3–5 m below the sea-water surface. This study provides new information for further investigation of osmo- and mechanosensation in Aplysia californica. |
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Keywords: | Osmoreceptors Osphradium Retrograde labeling Septate junctions Aplysia californica |
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