GOLGI-STUDY OF THE TELENCEPHALON OF THE SMALL-SPOTTED DOGFISH SCYLIORHINUS-CANICULA L

The telencephalon of the small-spotted dogfish, Scyliorhinus canicula L., was examined by Nissl and Golgi-aldehyde techniques. On the basis of differences in perikaryal and dendritic morphology and size, severa l cell types were distinguished in pallial and subpallial regions, mos t of them reported here for the first time in elasmobranchs. In the pa llium, the pallium dorsalis is the richest in cell types (eight types of neurons), whereas the neuron population of the pallium medialis is the most homogeneous. Dendrites of most neuron types in the pallium ar e smooth or sparsely thorny. Interestingly, the pallium dorsalis and p allium lateralis contain a type of primitive pyramidal cell characteri zed by the dense appearance of its thorny dendrites. In the subpallium , the area superficialis basalis contains a heterogeneous population ( six types of neurons): large radial cells are the most characteristic cell type. Dendrites of these cell types are smooth or sparsely thorny . The cell populations of the nucleus N are roughly similar to those o f the area superficialis basalis, but they lack the large radial cells characteristic of this area. The area centralis subpallialis and stri atum consist of populations of small neurons. The regio septalis conta ins a rather homogeneous population of small cells. The populations in the nucleus entopeduncularis and the nucleus interstitialis of the ba sal forebrain bundle are the least varied and consist of large radial cells and bipolar cells similar to those of the area superficialis bas alis. This investigation reveals important differences in cytoarchitec ture that should be useful in the interpretation of immunocytochemical , tracing, and electrophysiological studies of the telencephalon of el asmobranchs.