POSSIBLE MULTIPLE EVOLUTION OF INDIRECT TELENCEPHALO-CEREBELLAR PATHWAYS IN TELEOSTS - STUDIES IN CARASSIUS-AURATUS AND PANTODON BUCHHOLZI

Among vertebrates, telencephalo-pontine systems exist only in birds an d mammals. However, three nuclei in the diencephalon and mesencephalon of teleost fishes have been indicated - analogous to the pons - to re present relay stations between telencephalon and cerebellum. Since two of these nuclei (dorsal preglomerular nucleus, dorsal tegmental nucle us) have only been described in the highly derived, electrosensory mor myrids, we investigated telencephalic connections in two nonelectrosen sory teleosts, the goldfish Carassius auratus and the freshwater butte rflyfish Pantodon buchholzi, and cerebellar connections only in the la tter species, since for C. auratus these connections are already estab lished. Horseradish peroxidase tracing reveals that C. auratus has a d orsal tegmental nucleus and a paracommissural nucleus both of which ar e telencephalo-recipient and project to the cerebellum, and that P. bu chholzi has a dorsal preglomerular nucleus with such connections. Thes e results extend our knowlegde of the distribution and, therefore, the phylogeny of telencephalo-cerebellar systems in teleosts. Similar to tetrapods, teleosts appear to have developed telencephalo-cerebellar s ystems several times independently.