title: The neocortex of cetartiodactyls: I. A comparative Golgi analysis of neuronal morphology in the bottlenose dolphin (Tursiops truncatus), the minke whale (Balaenoptera acutorostrata), and the humpback whale (Megaptera novaeangliae).
abstract: The present study documents the morphology of neurons in several regions of the neocortex from the bottlenose dolphin (Tursiops truncatus), the North Atlantic minke whale (Balaenoptera acutorostrata), and the humpback whale (Megaptera novaeangliae). Golgi-stained neurons (n = 210) were analyzed in the frontal and temporal neocortex as well as in the primary visual and primary motor areas. Qualitatively, all three species exhibited a diversity of neuronal morphologies, with spiny neurons including typical pyramidal types, similar to those observed in primates and rodents, as well as other spiny neuron types that had more variable morphology and/or orientation. Five neuron types, with a vertical apical dendrite, approximated the general pyramidal neuron morphology (i.e., typical pyramidal, extraverted, magnopyramidal, multiapical, and bitufted neurons), with a predominance of typical and extraverted pyramidal neurons. In what may represent a cetacean morphological apomorphy, both typical pyramidal and magnopyramidal neurons frequently exhibited a tri-tufted variant. In the humpback whale, there were also large, star-like neurons with no discernable apical dendrite. Aspiny bipolar and multipolar interneurons were morphologically consistent with those reported previously in other mammals. Quantitative analyses showed that neuronal size and dendritic extent increased in association with body size and brain mass (bottlenose dolphin < minke whale < humpback whale). The present data thus suggest that certain spiny neuron morphologies may be apomorphies in the neocortex of cetaceans as compared to other mammals and that neuronal dendritic extent covaries with brain and body size.
authors.affiliation: Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, Box 1639, One Gustave L. Levy Place, New York, NY, 10029, USA. butticamilla@gmail.com.
authors.forename: Camilla
authors.initials: C
authors.lastname: Butti
authors.affiliation: Laboratory of Quantitative Neuromorphology, Psychology, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO, 80903, USA.
authors.forename: Caroline M
authors.initials: CM
authors.lastname: Janeway
authors.affiliation: Laboratory of Quantitative Neuromorphology, Psychology, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO, 80903, USA.
authors.forename: Courtney
authors.initials: C
authors.lastname: Townshend
authors.affiliation: Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, Box 1639, One Gustave L. Levy Place, New York, NY, 10029, USA.
authors.forename: Bridget A
authors.initials: BA
authors.lastname: Wicinski
authors.affiliation: Center for Anatomy and Functional Morphology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA.
authors.forename: Joy S
authors.initials: JS
authors.lastname: Reidenberg
authors.affiliation: National Marine Mammal Foundation, 2240 Shelter Island Drive, San Diego, CA, 92106, USA.
authors.forename: Sam H
authors.initials: SH
authors.lastname: Ridgway
authors.affiliation: Department of Anthropology, The George Washington University, 2110 G Street NW, Washington, DC, 20052, USA.
authors.forename: Chet C
authors.initials: CC
authors.lastname: Sherwood
authors.affiliation: Fishberg Department of Neuroscience and Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, Box 1639, One Gustave L. Levy Place, New York, NY, 10029, USA.
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Hof
authors.affiliation: Laboratory of Quantitative Neuromorphology, Psychology, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO, 80903, USA.
authors.forename: Bob
authors.initials: B
authors.lastname: Jacobs
mesh_terms: D000818:Animals; D050681:Bottle-Nosed Dolphin / Q000033:anatomy & histology* / Q000502:physiology; D003712:Dendrites / Q000502:physiology / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000502:physiology*; D050640:Humpback Whale / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D050636:Minke Whale / Q000033:anatomy & histology* / Q000502:physiology; D019579:Neocortex / Q000033:anatomy & histology / Q000166:cytology* / Q000648:ultrastructure; D009474:Neurons / Q000166:cytology / Q000648:ultrastructure; D017966:Pyramidal Cells / Q000166:cytology / Q000648:ultrastructure
keywords: Brain evolution; Cetacean neocortex; Golgi method; Neuronal morphology