Evolution of the brain in fishes.
Résumé
Study of brain evolution across and within each of the major radiations of fishes reveals a Bauplan or morphotype of the fish brain that exhibits many common ancestral neural traits – e.g. cranial nerves, brain subdivisions and the basic organization of ascending sensory pathways and of neurochemical phenotype distribution – shared by all craniates/vertebrates. At the same time many variations are revealed. The latter include substantial differences in pallial cytoarchitecture, tectal and cerebellar organization and emphasis of primary sensory centers. In sum, these findings are not consistent with the previously held notion of a linear Scala naturae in vertebrate brain evolution but rather with an appreciation of independent evolutionary events that have occurred on the foundations of the morphotype across and within different vertebrate radiations.