A Comparison of the Cortical Structure of the Bowhead Whale ( Balaena mysticetus ), a Basal Mysticete, with Other Cetaceans

Mary Ann Raghanti, Bridget Wicinski, Rachel Meierovich, Tahia Warda, Dara L. Dickstein, Joy S. Reidenberg, Cheuk Y. Tang, John C. George, J.G.M. Hans Thewissen, Camilla Butti, Patrick R. Hof
2018 The Anatomical Record  
Few studies exist of the bowhead whale brain and virtually nothing is known about its cortical cytoarchitecture or how it compares to other cetaceans. Bowhead whales are one of the least encephalized cetaceans and occupy a basal phylogenetic position among mysticetes. Therefore, the bowhead whale is an important specimen for understanding the evolutionary specializations of cetacean brains. Here, we present an overview of the structure and cytoarchitecture of the bowhead whale cerebral cortex
more » ... eaned from Nissl-stained sections and magnetic resonance imaging (MRI) in comparison with other mysticetes and odontocetes. In general, the cytoarchitecture of cetacean cortex is consistent in displaying a thin cortex, a thick, prominent layer I, and absence of a granular layer IV. Cell density, composition, and width of layers III, V, and VI vary among cortical regions, and cetacean cortex is cell-sparse relative to that of terrestrial mammals. Notably, all regions of the bowhead cortex possess high numbers of von Economo neurons and fork neurons, with the highest numbers observed at the apex of gyri. The bowhead whale is also distinctive in having a significantly reduced hippocampus that occupies a space below the corpus callosum within the lateral ventricle. Consistent with other balaenids, bowhead
doi:10.1002/ar.23991 pmid:30332717 fatcat:vgqvn527cjhvdihbzvrhzn43sa