Cetacean brains: How aquatic are they?

  title={Cetacean brains: How aquatic are they?},
  author={Lori Marino},
  journal={The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology},
  • L. Marino
  • Published 1 June 2007
  • Biology, Environmental Science
  • The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology
The adaptation of cetaceans to a fully aquatic lifestyle represents one of the most dramatic transformations in mammalian evolutionary history. Two of the most salient features of modern cetaceans are their fully aquatic lifestyle and their large brains. This review article will offer an overview of comparative neuroanatomical research on aquatic mammals, including analyses of odontocete cetacean, sirenian, pinniped, and fossil archaeocete brains. In particular, the question of whether a… 
The neocortex of cetaceans: cytoarchitecture and comparison with other aquatic and terrestrial species
The evolutionary process of readaptation to the aquatic environment was accompanied by extreme anatomical and physiological changes in the brain. This review discusses cortical specializations in the
Co‐evolution of cerebral and cerebellar expansion in cetaceans
The results suggest that major increases in both cerebrum and cerebellum size occurred early in cetacean evolution, prior to the origin of the major extant clades, and predate the evolution of echolocation.
It is suggested that cetacean brain and body mass evolved under strong directional trends to increase through time, but decreases in EQ were widespread, and that until recently the most encephalized mammals were odontocetes, not primates.
The size and complexity of dolphin brains—a paradox?
  • S. Huggenberger
  • Biology
    Journal of the Marine Biological Association of the United Kingdom
  • 2008
It is suggested that the evolution of the large dolphin brain was possible due to a combination of different prerequisites based on adaptations to the aquatic environment including the sonar system and the rudimentary pelvic girdle did not limit brain size at birth.
The Cerebral Cortex of the Pygmy Hippopotamus, Hexaprotodon liberiensis (Cetartiodactyla, Hippopotamidae): MRI, Cytoarchitecture, and Neuronal Morphology
The present study provides a comprehensive dataset of the neuroanatomy of H. liberiensis that sets the ground for future comparative studies including the larger Hippopotamus amphibius.
The pattern of brain-size change in the early evolution of cetaceans
The data show that brain size increased at the origin of basilosaurids, 5 million years before the Eocene-Oligocene transition, and it is suggested that cetacean relative brain size is most accurately portrayed using EQs based on the scaling coefficients as observed in the closely related terrestrial artiodactyls.
Positive selection at the ASPM gene coincides with brain size enlargements in cetaceans
It is of particular interest to find that positive selection was restricted to cetaceans and primates, two distant lineages both characterized by a massive expansion of brain size.
Anatomical adaptations of aquatic mammals
The articles in this issue are a blend of literature review and new, hypothesis‐driven anatomical research, which highlight the special nature of anatomical form and function in aquatic mammals that enables their exquisite adaptation for life in such a challenging environment.
The Evolution of Brains and Cognitive Abilities
It is proposed that the weight of evidence suggests that social intelligence is limited to relatively fewTaxa, such as primates and cetaceans, and that across other taxa, a variety of other factors have driven the evolution of advanced intelligence in animals.
Delphinid brain development from neonate to adulthood with comparisons to other cetaceans and artiodactyls
Delphinids’ larger brain growth dur- ing life at sea may be explained by at least three differences from artiodactyls’ life on land, which likely result in a larger delphinid brain.


Cortical complexity in cetacean brains.
  • P. Hof, R. Chanis, L. Marino
  • Biology, Psychology
    The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology
  • 2005
Data on brain size and hemisphere surface configuration in several cetacean species are summarized and an overview of the cytoarchitectural complexity of the cerebral cortex of the bottlenose dolphin is presented.
Origin and evolution of large brains in toothed whales.
  • L. Marino, D. McShea, M. Uhen
  • Biology, Environmental Science
    The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology
  • 2004
It is shown that brain size increased significantly in two critical phases in the evolution of odontocetes, and was accompanied by a decrease in body size in Delphinoidea only by 15 million years ago.
Brain Size Evolution
Evolution of marine mammals: Back to the sea after 300 million years
  • M. Uhen
  • Environmental Science, Biology
    Anatomical record
  • 2007
The earliest representatives of these clades all show morphological features that indicate they were feeding while in the water, suggesting that feeding ecology is a key factor in the evolution of marine mammals.
Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls
Cladistic analysis of the skeletons of two early Eocene pakicetid cetaceans, the fox-sized Ichthyolestes pinfoldi, and the wolf-sized Pakicetus attocki, indicates that cetACEans are more closely related to artiodactyls than to any mesonychian, and supports monophyly of artiodACTyls.
A Comparison of Encephalization between Odontocete Cetaceans and Anthropoid Primates
  • L. Marino
  • Psychology, Biology
    Brain, Behavior and Evolution
  • 1998
Results show that the encephalization level of Homo sapiens is still extraordinary relative to that of nonhuman species, but a subset of delphinid odontocetes are significantly more highly encephalized than the most highlyEncephalized anthropoid primates and narrow the gap in encephalizations between humans and nonhumans substantially.
Morphogenesis of the brain in the harbour porpoise
Investigation of reconstructions from serial sections of successive prenatal stages of the harbour porpoise revealed that a common ontogenetic plan regarding the chronological sequence of morphogenetic events exists in mammalian orders as different as primates and odontocetes.
The Auditory Central Nervous System of Dolphins
Although there have been no specific studies on hearing by the cetacean fetus, clearly other mammals have demonstrated a capability to hear in the womb well before birth.
Magnetic resonance images of the brain of a dwarf sperm whale (Kogia simus)
This paper represents the first MRI‐based anatomically labelled three‐dimensional description of the dwarf sperm whale brain and displays the proportions and positions of major neuroanatomical features.