Quantitative analysis of neocortical gyrencephaly in African elephants (Loxodonta africana) and six species of cetaceans: Comparison with other mammals
Version of Record online: 14 MAY 2012
Copyright © 2012 Wiley Periodicals, Inc.
Journal of Comparative Neurology
Volume 520, Issue 11, pages 2430–2439, 1 August 2012
How to Cite
Manger, P. R., Prowse, M., Haagensen, M. and Hemingway, J. (2012), Quantitative analysis of neocortical gyrencephaly in African elephants (Loxodonta africana) and six species of cetaceans: Comparison with other mammals. J. Comp. Neurol., 520: 2430–2439. doi: 10.1002/cne.23046
- Issue online: 14 MAY 2012
- Version of Record online: 14 MAY 2012
- Accepted manuscript online: 11 JAN 2012 07:23AM EST
- Manuscript Accepted: 7 JAN 2012
- Manuscript Revised: 10 DEC 2011
- Manuscript Received: 7 NOV 2011
- South African National Research Foundation. Grant Number: FA2005033100004
- cerebral hemisphere;
This study provides quantitative data on the extent of gyrencephaly in the large-brained African elephant and several species of cetaceans (from smaller to larger brained) in comparison with other mammals. Across three mammalian orders (primates, carnivores, and artiodactyls), the species with the larger brains are more gyrencephalic with each order, exhibiting a specific negative allometry. The African elephant, with a 5-kg brain, has a gyrencephalic index (GI) of 3.89, which, though highly gyrencephalic, is not more so than would be predicted for a mammal with a 5-kg brain. The cetaceans had an average GI of 5.43, are the most gyrencephalic mammals studied to date, and are more gyrencephalic than one would predict based on comparison with other mammals. No relationship between brain mass and GI was evident in the cetaceans as seen in other mammals, with all cetaceans showing similar GIs irrespective of brain mass (range of GI 5.23–5.70, range of brain mass 577–5617 g). This is yet another parameter indicating cetaceans to be neuroanatomical outliers. Two species of pinnipeds studied had GIs that were well above those seen for terrestrial carnivores, and the aquatic manatee was close to lissencephalic. Thus, all three groups of marine mammals showed unusual extents of cortical gyrencephaly, indicating a morphological alteration of the telencephalon associated with the return to the marine environment. The analysis suggests that cortical thickness and neuronal density are important factors in determining the extent of gyrencephaly across mammalian species. J. Comp. Neurol. 520:2430–2439, 2012. © 2012 Wiley Periodicals Inc.