Quarterly Journal of Microscopical Science, Vol s3-103, 211-226, Copyright © 1962 by Company of Biologists

Neurosecretory Cells in the Optic Tentacles of Certain Pulmonates

¹ Cytological Laboratory, Department of Zoology, University Museum, Oxford

Cells considered to be neurosecretory have been observed in the optic tentacles of certain stylommatophoran pulmonates. Such cells are divisible into three distinct types, of which those called the ‘collar’ cells surround the central digitate ganglion and eye. The other two types, the ‘lateral oval’ and the ‘lateral processed’ cells, lie laterally in the tentacle, on the inner edge of the outer dermo-muscular sheath. All three cell-types have branching dendritic processes, containing granules. The dendrites of the collar and of the lateral cells apparently extend from the cell-body to the surface of the epithelium. The axonal processes of all three types are thick and contain granules.

The ground cytoplasm of these cells is scarcely visible owing to the great number of homogeneous, spheroidal granules that are present. The granules are sudanophil, and the ones in the collar cells contain phospholipid (probably cerebroside as well). All three types of cells contain a much smaller number of lipid droplets, with sudanophil and osmiophil externum and sudanophobe and osmiophobe internum; these are dispersed through the cytoplasm. Special ‘perinuclear bodies’, also binary in structure, are present in the collar cells and lateral oval cells.

Cells of the types described in this paper have not been found in other sub-classes of the Gastropoda, nor in the Basommatophora, but only in the pulmonate order, Stylommatophora. They appear to form an area of active neurosecretion in the retractile tentacles of these animals.