Ultrastructure of the sensory epithelium in the chemoreceptor-areas of the tentacle of Onchidella celtica Cuv. (Pulmonata, Onchidiacea)
Wondrak, G.
Zeitschrift für Mikroskopisch-Anatomische Forschung 98(4): 551-565
1984
ISSN/ISBN: 0044-3107 PMID: 6524008 Document Number: 225215
In the investigated O. celtica a transverse furrow divides the surface of the tentacular terminal knob in a dorsal and a ventral chemoreceptor area. Both are covered by a sensory epithelium that consists of support cells, primary sensory cells and glandular collar cells. The perikarya of the sensory cells are situated in a layer underneath the base of the epithelium, separated from that by a thin muscle layer. The apical projections of the columnar support cells are 1-2 times dichotomously branched and thus most projections have 2-6 tips (the average ratio of projections to their tips is 4: 13), referred to as terminal twigs. Only those are enveloped by the surface coat. The cytofila and cilia of dendrites are confined to the underlying space, where they form a spongy layer. Two dendrite types are present. The 1st type has 1-2 cilia and numerous long 70 nm thick cytofila. A 2nd type with .apprx. 10 cilia has few short 110 nm thick cytofila. Underneath the perikarya of the sensory cells are found the somata of glandular collar cells up to 100 .mu.m large. In order to reach the surface, their ducts pierce the layer of sensory cell perikarya, the muscle cell layer of epithalial cells as very fine tubules. All the epithelial cells have apically anular junctions consisting of a zonula adhaerens and a zonula septata. A genetical relationship of O. celtica with that group of pulmonates consisting of archaeopulmonates, systellomatophorans and stylomatophoransis.