Mesencephalic and diencephalic cobalt-lysine injections in an elasmobranch: evidence for two parallel electrosensory pathways.

Iontophoretic injections of cobaltous lysine have revealed a direct projection from the electroreceptive lateral mesencephalic nucleus to the ipsilateral diencephalic posterior lateral nucleus in the thornback ray, Platyrhinoidis triseriata. Since it is known that the latter nucleus projects to the contralateral pallium, this completes the anatomical description of an electrosensory pathway from receptors to telencephalon in an elasmobranch. In addition, diencephalic injections into the electroreceptive anterior nucleus indicate there is a second, parallel electrosensory system which projects to the hypothalamus.