Light and electron microscopic investigation of the sensory dendrites in the epidermis of the foot of the snail, Helix pomatia L.

The fine structure of epithelial cells, supporting cells and the sensory dendrites running toward the surface between the former two was investigated in the epidermis of the foot of Helix pomatia. Cilia orienting in regular lines and possessing 9 + 2 tubular structure occur on the surface of the cylindrical epithelial cells lying on the basal lamina. The cilia terminate in basal bodies. The epithelial cells can first of all be characterized by a well-developed Golgi-apparatus and endoplasmic reticulum system as well as a developed tonofibrillar system. The supporting cells differ from the epithelial cells mainly in the poorly-developed tonofibrillar system and small number of cilia. Septate desmosome and zonula adherens are the common connecting structures between the cells composing the epithelium. According to the surface specialization, two types of sensory dendrites running toward the surface were distinguished: dendrites with and dendrites without cilia. On the surface of the former cilia with 9 + 2 tubular structure are randlomly distributed and are present in varying number. In their cytoplasm there are many mitochondria, few clear vesicles and multivesicular bodies. From the surface of the dendrites without cilia, microvilli of different diameter originate and sometimes a centriole was observed below the distal membrane. Their cytoplasm contains many clear vesicles, a well developed smooth endoplasmic reticulum system and few mitochondria. Comparing our results with literary data, we suppose that the differences between the two dendrite types in the presence and number of cilia as well as in the diameter of the microvilli show different forms of appearance of one type of dendritic terminal.