The Connections of the Telencephalic Pallium in the White Sturgeon, Acipenser transmontanus : An Experimental Study

ABSTRACT

Sturgeons are an ancient and basal group of ray‐finned fishes whose morphology is critical to our understanding of the evolution of teleosts, which form most of the ray‐finned fish radiation. In sturgeons, the pallium, or area dorsalis, consists of lateral, medial, and posterior divisions. The connections of these pallial divisions were determined by injections of biotinylated dextran amine and DiI. All three divisions receive olfactory input, with the posterior division receiving the bulk of the secondary olfactory projections. All three pallial divisions also have extensive intratelencephalic connections, as well as input from the thalamus and the posterior tubercle. The posterior division also receives sparse input from the midbrain and secondary gustatory nucleus of the isthmus. All three pallial divisions project heavily to the hypothalamus of the ipsilateral inferior lobe, and more sparsely to the ipsilateral optic tectum, posterior tubercle, and midbrain tegmentum. Cytological and connectional data provide no evidence that either a dorsal or central pallial division exists in sturgeons, and these pallial divisions likely arose in ancestral teleosts.