51
|
Dell LA, Spocter MA, Patzke N, Karlson KÆ, Alagaili AN, Bennett NC, Muhammed OB, Bertelsen MF, Siegel JM, Manger PR. Orexinergic bouton density is lower in the cerebral cortex of cetaceans compared to artiodactyls. J Chem Neuroanat 2015; 68:61-76. [DOI: 10.1016/j.jchemneu.2015.07.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Revised: 06/29/2015] [Accepted: 07/22/2015] [Indexed: 12/25/2022]
|
52
|
Gingerich PD. Body Weight and Relative Brain Size (Encephalization) in Eocene Archaeoceti (Cetacea). J MAMM EVOL 2015. [DOI: 10.1007/s10914-015-9304-y] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
53
|
Corfield JR, Price K, Iwaniuk AN, Gutierrez-Ibañez C, Birkhead T, Wylie DR. Diversity in olfactory bulb size in birds reflects allometry, ecology, and phylogeny. Front Neuroanat 2015; 9:102. [PMID: 26283931 PMCID: PMC4518324 DOI: 10.3389/fnana.2015.00102] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Accepted: 07/13/2015] [Indexed: 12/20/2022] Open
Abstract
The relative size of olfactory bulbs (OBs) is correlated with olfactory capabilities across vertebrates and is widely used to assess the relative importance of olfaction to a species’ ecology. In birds, variations in the relative size of OBs are correlated with some behaviors; however, the factors that have led to the high level of diversity seen in OB sizes across birds are still not well understood. In this study, we use the relative size of OBs as a neuroanatomical proxy for olfactory capabilities in 135 species of birds, representing 21 orders. We examine the scaling of OBs with brain size across avian orders, determine likely ancestral states and test for correlations between OB sizes and habitat, ecology, and behavior. The size of avian OBs varied with the size of the brain and this allometric relationship was for the most part isometric, although species did deviate from this trend. Large OBs were characteristic of more basal species and in more recently derived species the OBs were small. Living and foraging in a semi-aquatic environment was the strongest variable driving the evolution of large OBs in birds; olfaction may provide cues for navigation and foraging in this otherwise featureless environment. Some of the diversity in OB sizes was also undoubtedly due to differences in migratory behavior, foraging strategies and social structure. In summary, relative OB size in birds reflect allometry, phylogeny and behavior in ways that parallel that of other vertebrate classes. This provides comparative evidence that supports recent experimental studies into avian olfaction and suggests that olfaction is an important sensory modality for all avian species.
Collapse
Affiliation(s)
- Jeremy R Corfield
- Department of Psychology, University of Alberta, Edmonton AB, Canada ; Department of Neuroscience, University of Lethbridge, Lethbridge AB, Canada
| | - Kasandra Price
- Department of Psychology, University of Alberta, Edmonton AB, Canada
| | - Andrew N Iwaniuk
- Department of Neuroscience, University of Lethbridge, Lethbridge AB, Canada
| | | | - Tim Birkhead
- Department of Animal and Plant Sciences, University of Sheffield Sheffield, UK
| | - Douglas R Wylie
- Department of Psychology, University of Alberta, Edmonton AB, Canada
| |
Collapse
|
54
|
|
55
|
Ridgway S, Samuelson D, Van Alstyne K, Price D. On doing two things at once: dolphin brain and nose coordinate sonar clicks, buzzes, and emotional squeals with social sounds during fish capture. J Exp Biol 2015; 218:3987-95. [DOI: 10.1242/jeb.130559] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Accepted: 10/13/2015] [Indexed: 11/20/2022]
Abstract
Dolphins fishing alone in open waters may whistle without interrupting their sonar clicks as they find and eat or reject fish. Our study is the first to match sound and video from the dolphin with sound and video from near the fish. During search and capture of fish, free-swimming dolphins carried cameras to record video and sound. A hydrophone in the far field near the fish also recorded sound. From these two perspectives, we studied the time course of dolphin sound production during fish capture. Our observations identify the instant of fish capture. There are three consistent acoustic phases: sonar clicks locate the fish; bout 0.4 sec before capture, the dolphin clicks become more rapid to form a second phase, the terminal buzz; at or just before capture, the buzz turns to an emotional squeal-the victory squeal, which may last 0.2 to 20 sec after capture. The squeals are pulse bursts that vary in duration, peak frequency, and amplitude. The victory squeal may be a reflection of emotion triggered by brain dopamine release. It may also affect prey to ease capture and or it may be a way to communicate the presence of food to other dolphins.
Dolphins also use whistles as communication or social sounds. Whistling during sonar clicking suggests that dolphins may be adept at doing two things at once. We know that dolphin brain hemispheres may sleep independently. Our results suggest that the two dolphin brain hemispheres may also act independently in communication.
Collapse
Affiliation(s)
- Sam Ridgway
- National Marine Mammal Foundation, 2240 Shelter Island Drive, Ste 200, San Diego, CA 92106, USA
| | - Dianna Samuelson
- National Marine Mammal Foundation, 2240 Shelter Island Drive, Ste 200, San Diego, CA 92106, USA
| | - Kaitlin Van Alstyne
- National Marine Mammal Foundation, 2240 Shelter Island Drive, Ste 200, San Diego, CA 92106, USA
| | - DruAnn Price
- National Marine Mammal Foundation, 2240 Shelter Island Drive, Ste 200, San Diego, CA 92106, USA
| |
Collapse
|
56
|
Mortensen HS, Pakkenberg B, Dam M, Dietz R, Sonne C, Mikkelsen B, Eriksen N. Quantitative relationships in delphinid neocortex. Front Neuroanat 2014; 8:132. [PMID: 25505387 PMCID: PMC4244864 DOI: 10.3389/fnana.2014.00132] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2014] [Accepted: 10/29/2014] [Indexed: 12/04/2022] Open
Abstract
Possessing large brains and complex behavioral patterns, cetaceans are believed to be highly intelligent. Their brains, which are the largest in the Animal Kingdom and have enormous gyrification compared with terrestrial mammals, have long been of scientific interest. Few studies, however, report total number of brain cells in cetaceans, and even fewer have used unbiased counting methods. In this study, using stereological methods, we estimated the total number of cells in the neocortex of the long-finned pilot whale (Globicephala melas) brain. For the first time, we show that a species of dolphin has more neocortical neurons than any mammal studied to date including humans. These cell numbers are compared across various mammals with different brain sizes, and the function of possessing many neurons is discussed. We found that the long-finned pilot whale neocortex has approximately 37.2 × 109 neurons, which is almost twice as many as humans, and 127 × 109 glial cells. Thus, the absolute number of neurons in the human neocortex is not correlated with the superior cognitive abilities of humans (at least compared to cetaceans) as has previously been hypothesized. However, as neuron density in long-finned pilot whales is lower than that in humans, their higher cell number appears to be due to their larger brain. Accordingly, our findings make an important contribution to the ongoing debate over quantitative relationships in the mammalian brain.
Collapse
Affiliation(s)
- Heidi S Mortensen
- Research Laboratory for Stereology and Neuroscience, Bispebjerg and Frederiksberg University Hospitals Copenhagen, Denmark ; Research Department, Environment Agency Torshavn, Faroe Islands
| | - Bente Pakkenberg
- Research Laboratory for Stereology and Neuroscience, Bispebjerg and Frederiksberg University Hospitals Copenhagen, Denmark
| | - Maria Dam
- Research Department, Environment Agency Torshavn, Faroe Islands
| | - Rune Dietz
- Department of Bioscience, Institute for Bioscience - Arctic Research Centre, Roskilde, University of Aarhus Roskilde, Denmark
| | - Christian Sonne
- Department of Bioscience, Institute for Bioscience - Arctic Research Centre, Roskilde, University of Aarhus Roskilde, Denmark
| | | | - Nina Eriksen
- Research Laboratory for Stereology and Neuroscience, Bispebjerg and Frederiksberg University Hospitals Copenhagen, Denmark
| |
Collapse
|
57
|
Butti C, Janeway CM, Townshend C, Wicinski BA, Reidenberg JS, Ridgway SH, Sherwood CC, Hof PR, Jacobs B. 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). Brain Struct Funct 2014; 220:3339-68. [PMID: 25100560 DOI: 10.1007/s00429-014-0860-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2014] [Accepted: 07/25/2014] [Indexed: 12/12/2022]
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.
Collapse
Affiliation(s)
- Camilla Butti
- 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.
| | - Caroline M Janeway
- Laboratory of Quantitative Neuromorphology, Psychology, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO, 80903, USA
| | - Courtney Townshend
- Laboratory of Quantitative Neuromorphology, Psychology, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO, 80903, USA
| | - Bridget A Wicinski
- 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
| | - Joy S Reidenberg
- Center for Anatomy and Functional Morphology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY, 10029, USA
| | - Sam H Ridgway
- National Marine Mammal Foundation, 2240 Shelter Island Drive, San Diego, CA, 92106, USA
| | - Chet C Sherwood
- Department of Anthropology, The George Washington University, 2110 G Street NW, Washington, DC, 20052, USA
| | - Patrick R Hof
- 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
| | - Bob Jacobs
- Laboratory of Quantitative Neuromorphology, Psychology, Colorado College, 14 E. Cache La Poudre, Colorado Springs, CO, 80903, USA
| |
Collapse
|
58
|
Kelley TC, Higdon JW, Ferguson SH. Large testes and brain sizes in odontocetes (order Cetacea, suborder Odontoceti): the influence of mating system on encephalization. CAN J ZOOL 2014. [DOI: 10.1139/cjz-2014-0044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Little is known about their mating systems, but odontocetes may utilize the same types of mating systems as terrestrial mammals. Species with relatively large testes are likely to be polygynandrous, while species with smaller testes and greater sexual size dimorphism (SSD) are predicted to be polygynous. The “Machiavellian intelligence or sexual conflict” hypothesis predicts that polygynadrous species also evolved larger brains both to coerce conspecifics to mate and to resist mating attempts by undesirable mates. The “costly tissue” hypothesis predicts that species investing heavily in testes invest less in brain tissue and vice versa to conserve energy. Residual testes and brain mass measurements were used to test the sexual conflict and costly tissue hypotheses in 40 species of odontocetes. Correlations were performed on both raw data and independent contrasts to control for phylogeny. There was a significant positive correlation between residual testes mass and SSD in both data sets, and between residual testes mass and residual brain mass in the non-phylogenetically controlled data set. Results indicate a negative relationship between increased testes masses and SSD in odontocetes. There was no support for the costly tissue hypothesis. Support for Machiavellian intelligence or sexual conflict hypothesis was found only when phylogenetic effects were not considered.
Collapse
Affiliation(s)
- Trish C. Kelley
- Department of Environment and Geography, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
| | - Jeff W. Higdon
- Higdon Wildlife Consulting, 912 Ashburn Street, Winnipeg, MB R3G 3C9, Canada
| | - Steven H. Ferguson
- Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB R3T 2N6, Canada
| |
Collapse
|
59
|
Raghanti MA, Spurlock LB, Treichler FR, Weigel SE, Stimmelmayr R, Butti C, Thewissen JGMH, Hof PR. An analysis of von Economo neurons in the cerebral cortex of cetaceans, artiodactyls, and perissodactyls. Brain Struct Funct 2014; 220:2303-14. [PMID: 24852852 DOI: 10.1007/s00429-014-0792-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2014] [Accepted: 04/29/2014] [Indexed: 10/25/2022]
Abstract
Von Economo neurons (VENs) are specialized projection neurons with a characteristic spindle-shaped soma and thick basal and apical dendrites. VENs have been described in restricted cortical regions, with their most frequent appearance in layers III and V of the anterior cingulate cortex, anterior insula, and frontopolar cortex of humans, great apes, macaque monkeys, elephants, and some cetaceans. Recently, a ubiquitous distribution of VENs was reported in various cortical areas in the pygmy hippopotamus, one of the closest living relatives of cetaceans. That finding suggested that VENs might not be unique to only a few species that possess enlarged brains. In the present analysis, we assessed the phylogenetic distribution of VENs within species representative of the superordinal clade that includes cetartiodactyls and perissodactyls, as well as afrotherians. In addition, the distribution of fork cells that are often found in close proximity to VENs was also assessed. Nissl-stained sections from the frontal pole, anterior cingulate cortex, anterior insula, and occipital pole of bowhead whale, cow, sheep, deer, horse, pig, rock hyrax, and human were examined using stereologic methods to quantify VENs and fork cells within layer V of all four cortical regions. VENs and fork cells were found in each of the species examined here with species-specific differences in distributions and densities. The present results demonstrated that VENs and fork cells were not restricted to highly encephalized or socially complex species, and their repeated emergence among distantly related species seems to represent convergent evolution of specialized pyramidal neurons. The widespread phylogenetic presence of VENs and fork cells indicates that these neuron morphologies readily emerged in response to selective forces,whose variety and nature are yet to be identified.
Collapse
Affiliation(s)
- Mary Ann Raghanti
- Department of Anthropology and School of Biomedical Sciences, Kent State University, 750 Hilltop Drive, 222 Lowry Hall, Kent, OH, 44242, USA,
| | | | | | | | | | | | | | | |
Collapse
|
60
|
Cozzi B, Roncon G, Granato A, Giurisato M, Castagna M, Peruffo A, Panin M, Ballarin C, Montelli S, Pirone A. The claustrum of the bottlenose dolphin Tursiops truncatus (Montagu 1821). Front Syst Neurosci 2014; 8:42. [PMID: 24734007 PMCID: PMC3975097 DOI: 10.3389/fnsys.2014.00042] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 03/10/2014] [Indexed: 02/04/2023] Open
Abstract
The mammalian claustrum is involved in processing sensory information from the environment. The claustrum is reciprocally connected to the visual cortex and these projections, at least in carnivores, display a clear retinotopic distribution. The visual cortex of dolphins occupies a position strikingly different from that of land mammals. Whether the reshaping of the functional areas of the cortex of cetaceans involves also modifications of the claustral projections remains hitherto unanswered. The present topographic and immunohistochemical study is based on the brains of eight bottlenose dolphins and a wide array of antisera against: calcium-binding proteins (CBPs) parvalbumin (PV), calretinin (CR), and calbindin (CB); somatostatin (SOM); neuropeptide Y (NPY); and the potential claustral marker Gng2. Our observations confirmed the general topography of the mammalian claustrum also in the bottlenose dolphin, although (a) the reduction of the piriform lobe modifies the ventral relationships of the claustrum with the cortex, and (b) the rotation of the telencephalon along the transverse axis, accompanied by the reduction of the antero-posterior length of the brain, apparently moves the claustrum more rostrally. We observed a strong presence of CR-immunoreactive (-ir) neurons and fibers, a diffuse but weak expression of CB-ir elements and virtually no PV immunostaining. This latter finding agrees with studies that report that PV-ir elements are rare in the visual cortex of the same species. NPY- and somatostatin-containing neurons were evident, while the potential claustral markers Gng2 was not identified in the sections, but no explanation for its absence is currently available. Although no data are available on the projections to and from the claustrum in cetaceans, our results suggest that its neurochemical organization is compatible with the presence of noteworthy cortical inputs and outputs and a persistent role in the general processing of the relative information.
Collapse
Affiliation(s)
- Bruno Cozzi
- Department of Comparative Biomedicine and Food Science, University of Padova Legnaro, Italy
| | - Giulia Roncon
- Department of Comparative Biomedicine and Food Science, University of Padova Legnaro, Italy
| | | | - Maristella Giurisato
- Department of Comparative Biomedicine and Food Science, University of Padova Legnaro, Italy
| | - Maura Castagna
- Department of Translational Research on New Technologies in Medicine and Surgery, University of Pisa Pisa, Italy
| | - Antonella Peruffo
- Department of Comparative Biomedicine and Food Science, University of Padova Legnaro, Italy
| | - Mattia Panin
- Department of Comparative Biomedicine and Food Science, University of Padova Legnaro, Italy
| | - Cristina Ballarin
- Department of Comparative Biomedicine and Food Science, University of Padova Legnaro, Italy
| | - Stefano Montelli
- Department of Comparative Biomedicine and Food Science, University of Padova Legnaro, Italy
| | - Andrea Pirone
- Department of Veterinary Sciences, University of Pisa Pisa, Italy
| |
Collapse
|
61
|
In contrast to many other mammals, cetaceans have relatively small hippocampi that appear to lack adult neurogenesis. Brain Struct Funct 2013; 220:361-83. [PMID: 24178679 DOI: 10.1007/s00429-013-0660-1] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 10/15/2013] [Indexed: 12/16/2022]
Abstract
The hippocampus is essential for the formation and retrieval of memories and is a crucial neural structure sub-serving complex cognition. Adult hippocampal neurogenesis, the birth, migration and integration of new neurons, is thought to contribute to hippocampal circuit plasticity to augment function. We evaluated hippocampal volume in relation to brain volume in 375 mammal species and examined 71 mammal species for the presence of adult hippocampal neurogenesis using immunohistochemistry for doublecortin, an endogenous marker of immature neurons that can be used as a proxy marker for the presence of adult neurogenesis. We identified that the hippocampus in cetaceans (whales, dolphins and porpoises) is both absolutely and relatively small for their overall brain size, and found that the mammalian hippocampus scaled as an exponential function in relation to brain volume. In contrast, the amygdala was found to scale as a linear function of brain volume, but again, the relative size of the amygdala in cetaceans was small. The cetacean hippocampus lacks staining for doublecortin in the dentate gyrus and thus shows no clear signs of adult hippocampal neurogenesis. This lack of evidence of adult hippocampal neurogenesis, along with the small hippocampus, questions current assumptions regarding cognitive abilities associated with hippocampal function in the cetaceans. These anatomical features of the cetacean hippocampus may be related to the lack of postnatal sleep, causing a postnatal cessation of hippocampal neurogenesis.
Collapse
|
62
|
Manger P. Questioning the interpretations of behavioral observations of cetaceans: Is there really support for a special intellectual status for this mammalian order? Neuroscience 2013; 250:664-96. [DOI: 10.1016/j.neuroscience.2013.07.041] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Accepted: 07/17/2013] [Indexed: 11/26/2022]
|
63
|
Manger PR, Spocter MA, Patzke N. The evolutions of large brain size in mammals: the 'over-700-gram club quartet'. BRAIN, BEHAVIOR AND EVOLUTION 2013; 82:68-78. [PMID: 23979457 DOI: 10.1159/000352056] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The current paper details our developing understanding of the evolution of large brains in mammals. In order to do this, we first define brains that we consider to be large--those that have passed the apparent 700-gram ceiling on brain mass evolution in the class Mammalia. The over-700-gram club includes certain species within the genus Homo, order Cetacea, order Proboscidea, and suborder Pinnipedia. Our analysis suggests that selection for body size appears to be the most important factor in the evolution of large brain size, but there also appear to be internal morphophysiological constraints on large brain size evolution that need to be overcome in order for brains to break the 700-gram barrier. These two aspects appear to be common themes in the evolution of large brains. This significantly diminishes the explanatory value of selection for greater cognitive capacities as a principal factor in the evolution of enlarged brain sizes above the 700-gram threshold.
Collapse
Affiliation(s)
- Paul R Manger
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, Republic of South Africa.
| | | | | |
Collapse
|
64
|
Montgomery SH, Geisler JH, McGowen MR, Fox C, Marino L, Gatesy J. The evolutionary history of cetacean brain and body size. Evolution 2013; 67:3339-53. [PMID: 24152011 DOI: 10.1111/evo.12197] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 06/13/2013] [Indexed: 11/30/2022]
Abstract
Cetaceans rival primates in brain size relative to body size and include species with the largest brains and biggest bodies to have ever evolved. Cetaceans are remarkably diverse, varying in both phenotypes by several orders of magnitude, with notable differences between the two extant suborders, Mysticeti and Odontoceti. We analyzed the evolutionary history of brain and body mass, and relative brain size measured by the encephalization quotient (EQ), using a data set of extinct and extant taxa to capture temporal variation in the mode and direction of evolution. Our results suggest that cetacean brain and body mass evolved under strong directional trends to increase through time, but decreases in EQ were widespread. Mysticetes have significantly lower EQs than odontocetes due to a shift in brain:body allometry following the divergence of the suborders, caused by rapid increases in body mass in Mysticeti and a period of body mass reduction in Odontoceti. The pattern in Cetacea contrasts with that in primates, which experienced strong trends to increase brain mass and relative brain size, but not body mass. We discuss what these analyses reveal about the convergent evolution of large brains, and highlight that until recently the most encephalized mammals were odontocetes, not primates.
Collapse
Affiliation(s)
- Stephen H Montgomery
- Department of Zoology, University of Cambridge, Downing Street, Cambridge, United Kingdom.
| | | | | | | | | | | |
Collapse
|
65
|
Kelava I, Lewitus E, Huttner WB. The secondary loss of gyrencephaly as an example of evolutionary phenotypical reversal. Front Neuroanat 2013; 7:16. [PMID: 23805079 PMCID: PMC3693069 DOI: 10.3389/fnana.2013.00016] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 05/20/2013] [Indexed: 11/13/2022] Open
Abstract
Gyrencephaly (the folding of the surface of the neocortex) is a mammalian-specific trait present in almost all mammalian orders. Despite the widespread appearance of the trait, little is known about the mechanism of its genesis or its adaptive significance. Still, most of the hypotheses proposed concentrated on the pattern of connectivity of mature neurons as main components of gyri formation. Recent work on embryonic neurogenesis in several species of mammals revealed different progenitor and stem cells and their neurogenic potential as having important roles in the process of gyrification. Studies in the field of comparative neurogenesis revealed that gyrencephaly is an evolutionarily labile trait, and that some species underwent a secondary loss of a convoluted brain surface and thus reverted to a more ancient form, a less folded brain surface (lissencephaly). This phenotypic reversion provides an excellent system for understanding the phenomenon of secondary loss. In this review, we will outline the theory behind secondary loss and, as specific examples, present species that have undergone this transition with respect to neocortical folding. We will also discuss different possible pathways for obtaining (or losing) gyri. Finally, we will explore the potential adaptive consequence of gyrencephaly relative to lissencephaly and vice versa.
Collapse
Affiliation(s)
| | | | - Wieland B. Huttner
- Max Planck Institute of Molecular Cell Biology and GeneticsDresden, Germany
| |
Collapse
|
66
|
Rial R, González J, Gené L, Akaârir M, Esteban S, Gamundí A, Barceló P, Nicolau C. Asymmetric sleep in apneic human patients. Am J Physiol Regul Integr Comp Physiol 2013. [DOI: 10.1152/ajpregu.00302.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Unilateral sleep in marine mammals has been considered to be a defense against airway obstruction, as a sentinel for pod maintenance, and as a thermoregulatory mechanism. Birds also show asymmetric sleep, probably to avoid predation. The variable function of asymmetric sleep suggests a general capability for independence between brain hemispheres. Patients with obstructive sleep apnea share similar problems with diving mammals, but their eventual sleep asymmetry has received little attention. The present report shows that human sleep apnea patients also present temporary interhemispheric variations in dominance during sleep, with significant differences when comparing periods of open and closed airways. The magnitude of squared coherence, an index of interhemispheric EEG interdependence in phase and amplitude, rises in the delta EEG range during apneic episodes, while the phase lag index, a measure of linear and nonlinear interhemispheric phase synchrony, drops to zero. The L index, which measures generalized nonlinear EEG interhemispheric synchronization, increases during apneic events. Thus, the three indexes show significant and congruent changes in interhemispheric symmetry depending on the state of the airways. In conclusion, when confronted with a respiratory challenge, sleeping humans undergo small, but significant, breathing-related oscillations in interhemispheric dominance, similar to those observed in marine mammals. The evidence points to a relationship between cetacean unihemispheric sleep and their respiratory challenges.
Collapse
Affiliation(s)
- Rubén Rial
- Laboratori de Neurofisiología, Institut Universitari de Ciències de la Salut, Universitat de les Illes Balears, Palma, Majorca; and
| | - Julián González
- Departamento de Fisiología, Instituto de Tecnologías Biomédicas, Universidad de La Laguna, Tenerife, Spain
| | - Lluis Gené
- Laboratori de Neurofisiología, Institut Universitari de Ciències de la Salut, Universitat de les Illes Balears, Palma, Majorca; and
| | - Mourad Akaârir
- Laboratori de Neurofisiología, Institut Universitari de Ciències de la Salut, Universitat de les Illes Balears, Palma, Majorca; and
| | - Susana Esteban
- Laboratori de Neurofisiología, Institut Universitari de Ciències de la Salut, Universitat de les Illes Balears, Palma, Majorca; and
| | - Antoni Gamundí
- Laboratori de Neurofisiología, Institut Universitari de Ciències de la Salut, Universitat de les Illes Balears, Palma, Majorca; and
| | - Pere Barceló
- Laboratori de Neurofisiología, Institut Universitari de Ciències de la Salut, Universitat de les Illes Balears, Palma, Majorca; and
| | - Cristina Nicolau
- Laboratori de Neurofisiología, Institut Universitari de Ciències de la Salut, Universitat de les Illes Balears, Palma, Majorca; and
| |
Collapse
|
67
|
Maseko BC, Jacobs B, Spocter MA, Sherwood CC, Hof PR, Manger PR. Qualitative and Quantitative Aspects of the Microanatomy of the African Elephant Cerebellar Cortex. BRAIN, BEHAVIOR AND EVOLUTION 2013; 81:40-55. [DOI: 10.1159/000345565] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2012] [Accepted: 09/14/2012] [Indexed: 11/19/2022]
|
68
|
Schneuer M, Flachsbarth S, Czech-Damal NU, Folkow LP, Siebert U, Burmester T. Neuroglobin of seals and whales: evidence for a divergent role in the diving brain. Neuroscience 2012; 223:35-44. [PMID: 22864183 DOI: 10.1016/j.neuroscience.2012.07.052] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2012] [Revised: 07/25/2012] [Accepted: 07/25/2012] [Indexed: 11/25/2022]
Abstract
Although many physiological adaptations of diving mammals have been reported, little is known about how their brains sustain the high demands for metabolic energy and thus O(2) when submerged. A recent study revealed in the deep-diving hooded seal (Cystophora cristata) a unique shift of the oxidative energy metabolism and neuroglobin, a respiratory protein that is involved in neuronal hypoxia tolerance, from neurons to astrocytes. Here we have investigated neuroglobin in another pinniped species, the harp seal (Pagophilus groenlandicus), and in two cetaceans, the harbor porpoise (Phocoena phocoena) and the minke whale (Balaenoptera acutorostrata). Neuroglobin sequences, expression levels and patterns were compared with those of terrestrial relatives, the ferret (Mustela putorius furo) and the cattle (Bos taurus), respectively. Neuroglobin sequences of whales and seals only differ in two or three amino acids from those of cattle and ferret, and are unlikely to confer functional differences, e.g. in O(2) affinity. Neuroglobin is expressed in the astrocytes also of P. groenlandicus, suggesting that the shift of neuroglobin and oxidative metabolism is a common adaptation in the brains of deep-diving phocid seals. In the cetacean brain neuroglobin resides in neurons, like in terrestrial mammals. However, neuroglobin mRNA expression levels were 4-15 times higher in the brains of harbor porpoises and minke whales than in terrestrial mammals or in seals. Thus neuroglobin appears to play a specific role in diving mammals, but seals and whales have evolved divergent strategies to cope with cerebral hypoxia. The specific function of neuroglobin that conveys hypoxia tolerance may either relate to oxygen supply or protection from reactive oxygen species. The different strategies in seals and whales resulted from a divergent evolution and an independent adaptation to diving.
Collapse
Affiliation(s)
- M Schneuer
- Institute of Zoology and Zoological Museum, University of Hamburg, Martin-Luther-King-Platz 3, 20146 Hamburg, Germany
| | | | | | | | | | | |
Collapse
|
69
|
Dell LA, Patzke N, Bhagwandin A, Bux F, Fuxe K, Barber G, Siegel JM, Manger PR. Organization and number of orexinergic neurons in the hypothalamus of two species of Cetartiodactyla: a comparison of giraffe (Giraffa camelopardalis) and harbour porpoise (Phocoena phocoena). J Chem Neuroanat 2012; 44:98-109. [PMID: 22683547 PMCID: PMC3551539 DOI: 10.1016/j.jchemneu.2012.06.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 06/01/2012] [Accepted: 06/01/2012] [Indexed: 11/18/2022]
Abstract
The present study describes the organization of the orexinergic (hypocretinergic) neurons in the hypothalamus of the giraffe and harbour porpoise--two members of the mammalian Order Cetartiodactyla which is comprised of the even-toed ungulates and the cetaceans as they share a monophyletic ancestry. Diencephalons from two sub-adult male giraffes and two adult male harbour porpoises were coronally sectioned and immunohistochemically stained for orexin-A. The staining revealed that the orexinergic neurons could be readily divided into two distinct neuronal types based on somal volume, area and length, these being the parvocellular and magnocellular orexin-A immunopositive (OxA+) groups. The magnocellular group could be further subdivided, on topological grounds, into three distinct clusters--a main cluster in the perifornical and lateral hypothalamus, a cluster associated with the zona incerta and a cluster associated with the optic tract. The parvocellular neurons were found in the medial hypothalamus, but could not be subdivided, rather they form a topologically amorphous cluster. The parvocellular cluster appears to be unique to the Cetartiodactyla as these neurons have not been described in other mammals to date, while the magnocellular nuclei appear to be homologous to similar nuclei described in other mammals. The overall size of both the parvocellular and magnocellular neurons (based on somal volume, area and length) were larger in the giraffe than the harbour porpoise, but the harbour porpoise had a higher number of both parvocellular and magnocellular orexinergic neurons than the giraffe despite both having a similar brain mass. The higher number of both parvocellular and magnocellular orexinergic neurons in the harbour porpoise may relate to the unusual sleep mechanisms in the cetaceans.
Collapse
Affiliation(s)
- Leigh-Anne Dell
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, Johannesburg, South Africa
| | - Nina Patzke
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, Johannesburg, South Africa
| | - Adhil Bhagwandin
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, Johannesburg, South Africa
- Department of Psychiatry, University of California, Los Angeles, Neurobiology Research 151A3, Sepulveda VAMC, 16111 Plummer St, North Hills, CA 91343, USA
| | - Faiza Bux
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, Johannesburg, South Africa
| | - Kjell Fuxe
- Department of Neuroscience, Karolinska Institutet, Retzius väg 8, S-171 77 Stockholm, Sweden
| | - Grace Barber
- Department of Psychiatry, University of California, Los Angeles, Neurobiology Research 151A3, Sepulveda VAMC, 16111 Plummer St, North Hills, CA 91343, USA
| | - Jerome M. Siegel
- Department of Psychiatry, University of California, Los Angeles, Neurobiology Research 151A3, Sepulveda VAMC, 16111 Plummer St, North Hills, CA 91343, USA
| | - Paul R. Manger
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, Johannesburg, South Africa
| |
Collapse
|
70
|
Manger PR, Prowse M, Haagensen M, Hemingway J. Quantitative analysis of neocortical gyrencephaly in African elephants (Loxodonta africana) and six species of cetaceans: Comparison with other mammals. J Comp Neurol 2012; 520:2430-9. [DOI: 10.1002/cne.23046] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
71
|
Maseko BC, Spocter MA, Haagensen M, Manger PR. Elephants have relatively the largest cerebellum size of mammals. Anat Rec (Hoboken) 2012; 295:661-72. [PMID: 22282440 DOI: 10.1002/ar.22425] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2011] [Revised: 11/17/2011] [Accepted: 11/23/2011] [Indexed: 11/07/2022]
Abstract
The current study used MR imaging to determine the volume of the cerebellum and its component parts in the brain of three adult male African elephants (Loxodonta africana) and compared this with published data from Asian elephants and other mammalian species including odontocete cetaceans, primates, chiropterans, insectivores, carnivores, and artiodactyls. The cerebellum of the adult elephant has a volume of ∼925 mL (average of both African and Asian species). Allometric analysis indicates that the elephant has the largest relative cerebellum size of all mammals studied to date. In addition, both odontocete cetaceans and microchiropterans appear to have large relative cerebellar sizes. The vermal and hemispheric components of the African elephant cerebellum are both large relative to other mammals of similar brain size, however, for odontocete cetaceans the vermal component is small and the hemispheric component is large. These volumetric observations are related to life-histories and anatomies of the species investigated. The current study provides context for one aspect of the elephant brain in the broader picture of mammalian brain evolution.
Collapse
Affiliation(s)
- Busisiwe C Maseko
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, Johannesburg, Republic of South Africa
| | | | | | | |
Collapse
|
72
|
Bhagwandin A, Gravett N, Hemingway J, Oosthuizen M, Bennett N, Siegel J, Manger P. Orexinergic neuron numbers in three species of African mole rats with rhythmic and arrhythmic chronotypes. Neuroscience 2011; 199:153-65. [DOI: 10.1016/j.neuroscience.2011.10.023] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Revised: 10/06/2011] [Accepted: 10/13/2011] [Indexed: 10/16/2022]
|
73
|
Body and self in dolphins. Conscious Cogn 2011; 21:526-45. [PMID: 22105086 DOI: 10.1016/j.concog.2011.10.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 10/03/2011] [Accepted: 10/07/2011] [Indexed: 02/08/2023]
Abstract
In keeping with recent views of consciousness of self as represented in the body in action, empirical studies are reviewed that demonstrate a bottlenose dolphin's (Tursiops truncatus) conscious awareness of its own body and body parts, implying a representational "body image" system. Additional work reviewed demonstrates an advanced capability of dolphins for motor imitation of self-produced behaviors and of behaviors of others, including imitation of human actions, supporting hypotheses that dolphins have a sense of agency and ownership of their actions and may implicitly attribute those levels of self-awareness to others. Possibly, a mirror-neuron system, or its functional equivalent to that described in monkeys and humans, may mediate both self-awareness and awareness of others.
Collapse
|
74
|
Malkemper EP, Oelschläger HHA, Huggenberger S. The dolphin cochlear nucleus: topography, histology and functional implications. J Morphol 2011; 273:173-85. [PMID: 21987441 DOI: 10.1002/jmor.11013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 07/08/2011] [Accepted: 08/03/2011] [Indexed: 11/12/2022]
Abstract
Despite the outstanding auditory capabilities of dolphins, there is only limited information available on the cytology of the auditory brain stem nuclei in these animals. Here, we investigated the cochlear nuclei (CN) of five brains of common dolphins (Delphinus delphis) and La Plata dolphins (Pontoporia blainvillei) using cell and fiber stain microslide series representing the three main anatomical planes. In general, the CN in dolphins comprise the same set of subnuclei as in other mammals. However, the volume ratio of the dorsal cochlear nucleus (DCN) in relation to the ventral cochlear nucleus (VCN) of dolphins represents a minimum among the mammals examined so far. Because, for example, in cats the DCN is necessary for reflexive orientation of the head and pinnae towards a sound source, the massive restrictions in head movability in dolphins and the absence of outer ears may be correlated with the reduction of the DCN. Moreover, the same set of main neuron types were found in the dolphin CN as in other mammals, including octopus and multipolar cells. Because the latter two types of neurons are thought to be involved in the recognition of complex sounds, including speech, we suggest that, in dolphins, they may be involved in the processing of their communication signals. Comparison of the toothed whale species studied here revealed that large spherical cells were present in the La Plata dolphin but absent in the common dolphin. These neurons are known to be engaged in the processing of low-frequency sounds in terrestrial mammals. Accordingly, in the common dolphin, the absence of large spherical cells seems to be correlated with a shift of its auditory spectrum into the high-frequency range above 20 kHz. The existence of large spherical cells in the VCN of the La Plata dolphin, however, is enigmatic asthis species uses frequencies around 130 kHz.
Collapse
Affiliation(s)
- E P Malkemper
- Department of Anatomy III (Dr. Senckenbergische Anatomie), Johann Wolfgang Goethe University Frankfurt am Main, 60590 Frankfurt am Main, Germany
| | | | | |
Collapse
|
75
|
Butti C, Raghanti MA, Sherwood CC, Hof PR. The neocortex of cetaceans: cytoarchitecture and comparison with other aquatic and terrestrial species. Ann N Y Acad Sci 2011; 1225:47-58. [PMID: 21534992 DOI: 10.1111/j.1749-6632.2011.05980.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
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 three major lineages of marine mammals in comparison to related terrestrial and semiaquatic species. Different groups of marine mammals adopted a wide range of strategies to cope with the challenges of aquatic living. Cetaceans and hippopotamids possess a completely agranular neocortex in contrast to phocids and sirenians; vertical modules are observed in deep layers V and VI in manatees, cetaceans, phocids, and hippopotamids, but in different cortical areas; and clustering in layer II appears in the insular cortex of hippopotamids, phocids, and cetaceans. Finally, von Economo neurons are present in cetaceans, hippopotamids, sirenians, and some phocids, with specific, yet different, cortical distributions. The interpretation of the evolutionary and functional significance of such specializations, and their relationships with the degrees of adaptation to the aquatic environment and phylogeny, remain difficult to trace, at least until comprehensive data, including representative species from all of the major mammalian families, become available.
Collapse
Affiliation(s)
- Camilla Butti
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York, USA.
| | | | | | | |
Collapse
|
76
|
Frieden BR, Gatenby RA. Order in a multidimensional system. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:011128. [PMID: 21867134 PMCID: PMC3990234 DOI: 10.1103/physreve.84.011128] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2011] [Indexed: 05/31/2023]
Abstract
We show that any convex K-dimensional system has a level of order R that is proportional to its level of Fisher information I. The proportionality constant is 1/8 the square of the longest chord connecting two surface points of the system. This result follows solely from the requirement that R decrease under small perturbations caused by a coarse graining of the system. The form for R is generally unitless, allowing the order for different phenomena, or different representations (e.g., using time vs frequency) of a given phenomenom, to be compared objectively. Order R is also invariant to uniform magnification of the system. The monotonic contraction properties of R and I define an arrow of time and imply that they are entropies, in addition to their usual status as informations. This also removes the need for data, and therefore an observer, in derivations of nonparticipatory phenomena that utilize I. Simple graphical examples of the new order measure show that it measures as well the level of "complexity" in the system. Finally, an application to cell growth during enforced distortion shows that a single hydrocarbon chain can be distorted into a membrane having equal order or complexity. Such membranes are prime constituents of living cells.
Collapse
Affiliation(s)
- B Roy Frieden
- College of Optics, University of Arizona, Tucson, Arizona 85721, USA
| | | |
Collapse
|
77
|
McGowen MR, Montgomery SH, Clark C, Gatesy J. Phylogeny and adaptive evolution of the brain-development gene microcephalin (MCPH1) in cetaceans. BMC Evol Biol 2011; 11:98. [PMID: 21492470 PMCID: PMC3101173 DOI: 10.1186/1471-2148-11-98] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 04/14/2011] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Representatives of Cetacea have the greatest absolute brain size among animals, and the largest relative brain size aside from humans. Despite this, genes implicated in the evolution of large brain size in primates have yet to be surveyed in cetaceans. RESULTS We sequenced ~1240 basepairs of the brain development gene microcephalin (MCPH1) in 38 cetacean species. Alignments of these data and a published complete sequence from Tursiops truncatus with primate MCPH1 were utilized in phylogenetic analyses and to estimate ω (rate of nonsynonymous substitution/rate of synonymous substitution) using site and branch models of molecular evolution. We also tested the hypothesis that selection on MCPH1 was correlated with brain size in cetaceans using a continuous regression analysis that accounted for phylogenetic history. Our analyses revealed widespread signals of adaptive evolution in the MCPH1 of Cetacea and in other subclades of Mammalia, however, there was not a significant positive association between ω and brain size within Cetacea. CONCLUSION In conjunction with a recent study of Primates, we find no evidence to support an association between MCPH1 evolution and the evolution of brain size in highly encephalized mammalian species. Our finding of significant positive selection in MCPH1 may be linked to other functions of the gene.
Collapse
Affiliation(s)
- Michael R McGowen
- Department of Biology, University of California, Riverside, 92521, USA.
| | | | | | | |
Collapse
|
78
|
Walløe S, Eriksen N, Dabelsteen T, Pakkenberg B. A neurological comparative study of the harp seal (Pagophilus groenlandicus) and harbor porpoise (Phocoena phocoena) brain. Anat Rec (Hoboken) 2011; 293:2129-35. [PMID: 21077171 DOI: 10.1002/ar.21295] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The cetacean brain is well studied. However, few comparisons have been done with other marine mammals. In this study, we compared the harp seal (Pagophilus groenlandicus) and the harbor porpoise brain (Phocoena phocoena). Stereological methods were applied to compare three areas of interest: the entire neocortex and two subdivisions of the neocortex, the auditory and visual cortices. The total number of neurons and glial cells in the three regions was estimated. The main results showed that the harbor porpoise have an estimated 14.9 × 10(9) neocortical neurons and 34.8 × 10(9) neocortical glial cells, whereas the harp seal have 6.1 × 10(9) neocortical neurons and 17.5 × 10(9) neocortical glial cells. The harbor porpoise have significantly more neurons and glial cells in the auditory cortex than in the visual cortex, whereas the pattern was opposite for the harp seal. These results are the first to provide estimates of the number of neurons and glial cells in the neocortex of the harp seal and harbor porpoise brain and offer new data to the comparative field of mammalian brain evolution.
Collapse
Affiliation(s)
- Solveig Walløe
- Research Laboratory for Stereology and Neuroscience, Bispebjerg University Hospital, Copenhagen, Denmark.
| | | | | | | |
Collapse
|
79
|
Kern A, Siebert U, Cozzi B, Hof P, Oelschläger H. Stereology of the Neocortex in Odontocetes: Qualitative, Quantitative, and Functional Implications. BRAIN, BEHAVIOR AND EVOLUTION 2011; 77:79-90. [DOI: 10.1159/000323674] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2010] [Accepted: 12/13/2010] [Indexed: 11/19/2022]
|
80
|
Manger P, Hemingway J, Haagensen M, Gilissen E. Cross-sectional area of the elephant corpus callosum: comparison to other eutherian mammals. Neuroscience 2010; 167:815-24. [DOI: 10.1016/j.neuroscience.2010.02.066] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Revised: 02/22/2010] [Accepted: 02/23/2010] [Indexed: 10/19/2022]
|
81
|
Roth TC, Rattenborg NC, Pravosudov VV. The ecological relevance of sleep: the trade-off between sleep, memory and energy conservation. Philos Trans R Soc Lond B Biol Sci 2010; 365:945-59. [PMID: 20156818 PMCID: PMC2830243 DOI: 10.1098/rstb.2009.0209] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
All animals in which sleep has been studied express signs of sleep-like behaviour, suggesting that sleep must have some fundamental functions that are sustained by natural selection. Those functions, however, are still not clear. Here, we examine the ecological relevance of sleep from the perspective of behavioural trade-offs that might affect fitness. Specifically, we highlight the advantage of using food-caching animals as a system in which a conflict might occur between engaging in sleep for memory/learning and hypothermia/torpor to conserve energy. We briefly review the evidence for the importance of sleep for memory, the importance of memory for food-caching animals and the conflicts that might occur between sleep and energy conservation in these animals. We suggest that the food-caching paradigm represents a naturalistic and experimentally practical system that provides the opportunity for a new direction in sleep research that will expand our understanding of sleep, especially within the context of ecological and evolutionary processes.
Collapse
Affiliation(s)
- Timothy C Roth
- Department of Biology, University of Nevada, Reno, NV 89557, USA.
| | | | | |
Collapse
|
82
|
Raghanti MA, Spocter MA, Butti C, Hof PR, Sherwood CC. A comparative perspective on minicolumns and inhibitory GABAergic interneurons in the neocortex. Front Neuroanat 2010; 4:3. [PMID: 20161991 PMCID: PMC2820381 DOI: 10.3389/neuro.05.003.2010] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Accepted: 01/07/2010] [Indexed: 11/28/2022] Open
Abstract
Neocortical columns are functional and morphological units whose architecture may have been under selective evolutionary pressure in different mammalian lineages in response to encephalization and specializations of cognitive abilities. Inhibitory interneurons make a substantial contribution to the morphology and distribution of minicolumns within the cortex. In this context, we review differences in minicolumns and GABAergic interneurons among species and discuss possible implications for signaling among and within minicolumns. Furthermore, we discuss how abnormalities of both minicolumn disposition and inhibitory interneurons might be associated with neuropathological processes, such as Alzheimer's disease, autism, and schizophrenia. Specifically, we explore the possibility that phylogenetic variability in calcium-binding protein-expressing interneuron subtypes is directly related to differences in minicolumn morphology among species and might contribute to neuropathological susceptibility in humans.
Collapse
Affiliation(s)
- Mary Ann Raghanti
- Department of Anthropology and School of Biomedical Sciences, Kent State University Kent, OH, USA
| | | | | | | | | |
Collapse
|
83
|
Butti C, Sherwood CC, Hakeem AY, Allman JM, Hof PR. Total number and volume of Von Economo neurons in the cerebral cortex of cetaceans. J Comp Neurol 2009; 515:243-59. [PMID: 19412956 DOI: 10.1002/cne.22055] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Von Economo neurons (VENs) are a type of large, layer V spindle-shaped neurons that were previously described in humans, great apes, elephants, and some large-brained cetaceans. Here we report the presence of Von Economo neurons in the anterior cingulate (ACC), anterior insular (AI), and frontopolar (FP) cortices of small odontocetes, including the bottlenose dolphin (Tursiops truncatus), the Risso's dolphin (Grampus griseus), and the beluga whale (Delphinapterus leucas). The total number and volume of VENs and the volume of neighboring layer V pyramidal neurons and layer VI fusiform neurons were obtained by using a design-based stereologic approach. Two humpback whale (Megaptera novaeangliae) brains were investigated for comparative purposes as representatives of the suborder Mysticeti. Our results show that the distribution of VENs in these cetacean species is comparable to that reported in humans, great apes, and elephants. The number of VENs in these cetaceans is also comparable to data available from great apes, and stereologic estimates indicate that VEN volume follows in these cetacean species a pattern similar to that in hominids, the VENs being larger than neighboring layer V pyramidal cells and conspicuously larger than fusiform neurons of layer VI. The fact that VENs are found in species representative of both cetacean suborders in addition to hominids and elephants suggests that these particular neurons have appeared convergently in phylogenetically unrelated groups of mammals possibly under the influence of comparable selective pressures that influenced specifically the evolution of cortical domains involved in complex cognitive and social/emotional processes.
Collapse
Affiliation(s)
- Camilla Butti
- Department of Neuroscience, Mount Sinai School of Medicine, New York, New York 10029, USA
| | | | | | | | | |
Collapse
|
84
|
Huggenberger S, Rauschmann MA, Vogl TJ, Oelschläger HH. Functional Morphology of the Nasal Complex in the Harbor Porpoise (Phocoena phocoenaL.). Anat Rec (Hoboken) 2009; 292:902-20. [DOI: 10.1002/ar.20854] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
85
|
Marino L, Butti C, Connor RC, Fordyce RE, Herman LM, Hof PR, Lefebvre L, Lusseau D, McCowan B, Nimchinsky EA, Pack AA, Reidenberg JS, Reiss D, Rendell L, Uhen MD, Van der Gucht E, Whitehead H. A claim in search of evidence: reply to Manger's thermogenesis hypothesis of cetacean brain structure. Biol Rev Camb Philos Soc 2008; 83:417-40. [PMID: 18783363 DOI: 10.1111/j.1469-185x.2008.00049.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In a recent publication in Biological Reviews, Manger (2006) made the controversial claim that the large brains of cetaceans evolved to generate heat during oceanic cooling in the Oligocene epoch and not, as is the currently accepted view, as a basis for an increase in cognitive or information-processing capabilities in response to ecological or social pressures. Manger further argued that dolphins and other cetaceans are considerably less intelligent than generally thought. In this review we challenge Manger's arguments and provide abundant evidence that modern cetacean brains are large in order to support complex cognitive abilities driven by social and ecological forces.
Collapse
Affiliation(s)
- Lori Marino
- Neuroscience and Behavioural Biology Program, Emory University, Atlanta, GA, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
86
|
Oelschläger HHA. The dolphin brain--a challenge for synthetic neurobiology. Brain Res Bull 2007; 75:450-9. [PMID: 18331914 DOI: 10.1016/j.brainresbull.2007.10.051] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2007] [Accepted: 10/17/2007] [Indexed: 11/17/2022]
Abstract
Toothed whales (odontocetes) are a promising paradigm for neurobiology and evolutionary biology. The ecophysiological implications and structural adaptations of their brain seem to reflect the necessity of effective underwater hearing for echolocation (sonar), navigation, and communication. However, not all components of the auditory system are equally well developed. Other sensory systems are more or less strongly reduced such as the olfactory system and, as an exception among vertebrates, the vestibular system (the semicircular canals and vestibular nuclei). Additional outstanding features are: (1) the hypertrophy of the neocortex, pons, cerebellum (particularly the paraflocculus), the elliptic nucleus, the facial motor nucleus and the medial accessory inferior olive and (2) the reduction of the hippocampus. The screening of brain structures with respect to shared circuitry and shared size correlations resulted in central loops also known from other mammals which overlap in the cerebellum and serve in the integration and processing of sensory input. It is highly probable that for dolphin navigation the ascending auditory pathway, including the inferior colliculus and the medial geniculate body, is of utmost importance. The extended auditory neocortical fields project to the midbrain and rhombencephalon and may influence premotor and motor areas in such a way as to allow the smooth regulation of sound-induced and sound-controlled locomotor activity as well as sophisticated phonation. This sonar-guided acousticomotor system for navigation and vocalization in the aquatic environment may have been a major factor if not the key feature in the relative size increase seen in dolphin brains.
Collapse
Affiliation(s)
- Helmut H A Oelschläger
- Institute of Anatomy III (Dr. Senckenbergische Anatomie), University of Frankfurt am Main, Germany.
| |
Collapse
|
87
|
Herculano-Houzel S. Encephalization, neuronal excess, and neuronal index in rodents. Anat Rec (Hoboken) 2007; 290:1280-7. [PMID: 17847061 DOI: 10.1002/ar.20598] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Encephalization, or brain size larger than expected from body size, has long been considered to correlate with improved cognitive abilities across species and even intelligence. However, it is still unknown what characteristics of relatively large brains underlie their improved functions. Here, it is shown that more encephalized rodent species have the number of neurons expected for their brain size, but a larger number of neurons than expected for their body size. The number of neurons in excess relative to body size might be available for improved associative functions and, thus, be responsible for the cognitive advantage observed in more encephalized animals. It is further proposed that, if such neuronal excess does provide for improved cognitive abilities, then the total number of excess neurons in each species-here dubbed the neuronal index-should be a better indicator of cognitive abilities than the encephalization quotient (EQ). Because the neuronal index is a function of both the number of neurons expected from the size of the body and the absolute number of neurons in the brain, differences in this parameter across species that share similar EQs might explain why these often have different cognitive capabilities, particularly when comparing across mammalian orders.
Collapse
|
88
|
Oelschläger H, Haas-Rioth M, Fung C, Ridgway S, Knauth M. Morphology and Evolutionary Biology of the Dolphin ( Delphinus sp.) Brain – MR Imaging and Conventional Histology. BRAIN, BEHAVIOR AND EVOLUTION 2007; 71:68-86. [DOI: 10.1159/000110495] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2007] [Accepted: 07/05/2007] [Indexed: 11/19/2022]
|
89
|
Marino L, Connor RC, Fordyce RE, Herman LM, Hof PR, Lefebvre L, Lusseau D, McCowan B, Nimchinsky EA, Pack AA, Rendell L, Reidenberg JS, Reiss D, Uhen MD, Van der Gucht E, Whitehead H. Cetaceans have complex brains for complex cognition. PLoS Biol 2007; 5:e139. [PMID: 17503965 PMCID: PMC1868071 DOI: 10.1371/journal.pbio.0050139] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
A group of eminent cetacean researchers respond to headlines charging that dolphins might be "flippin' idiots". They examine behavioural, anatomical and evolutionary data to conclude that the large brain of cetaceans evolved to support complex cognitive abilities.
Collapse
Affiliation(s)
- Lori Marino
- Neuroscience and Behavioral Biology Program, Emory University, Atlanta, Georgia, United States of America.
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
90
|
Connor RC. Dolphin social intelligence: complex alliance relationships in bottlenose dolphins and a consideration of selective environments for extreme brain size evolution in mammals. Philos Trans R Soc Lond B Biol Sci 2007; 362:587-602. [PMID: 17296597 PMCID: PMC2346519 DOI: 10.1098/rstb.2006.1997] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Bottlenose dolphins in Shark Bay, Australia, live in a large, unbounded society with a fission-fusion grouping pattern. Potential cognitive demands include the need to develop social strategies involving the recognition of a large number of individuals and their relationships with others. Patterns of alliance affiliation among males may be more complex than are currently known for any non-human, with individuals participating in 2-3 levels of shifting alliances. Males mediate alliance relationships with gentle contact behaviours such as petting, but synchrony also plays an important role in affiliative interactions. In general, selection for social intelligence in the context of shifting alliances will depend on the extent to which there are strategic options and risk. Extreme brain size evolution may have occurred more than once in the toothed whales, reaching peaks in the dolphin family and the sperm whale. All three 'peaks' of large brain size evolution in mammals (odontocetes, humans and elephants) shared a common selective environment: extreme mutual dependence based on external threats from predators or conspecific groups. In this context, social competition, and consequently selection for greater cognitive abilities and large brain size, was intense.
Collapse
Affiliation(s)
- Richard C Connor
- Biology Department, University of Massachusetts at Dartmouth, North Dartmouth, MA 02747, USA.
| |
Collapse
|
91
|
Spocter MA, Manger PR. The use of cranial variables for the estimation of body mass in fossil hominins. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2007; 134:92-105. [PMID: 17568446 DOI: 10.1002/ajpa.20641] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Estimating body mass/size/weight remains a crucial precursor to the evaluation of relative brain size and to achieving an understanding of brain evolution in fossil species. Despite the obvious close association between the metrics of postcranial elements and body mass a number of factors combine to reduce their utility. This study examines the feasibility of cranial variables for predicting body mass. The use of traditional regression procedures, independent contrasts analysis, and variance partitioning all support the hypothesis that cranial variables are correlated with body mass even when taking phylogeny into account, with r values typically ranging between 0.52 and 0.98. Body mass estimates derived for fossil hominins using cranial variables are similar to those obtained from previous studies using either cranial or postcranial elements. In particular, upper facial breadth and orbital height display strong predictive capability. Average body masses derived from Least Squares Regression (LSR) equations were used to calculate estimates of body mass for three hominin species. This resulted in estimates of between 30 kg and 47 kg for Australopithecus africanus, 48 kg and 52 kg for Paranthropus robustus, and 75 kg for Homo neanderthalensis. It is proposed that regression equations derived for the order primates are used to estimate body mass for archaic hominins, while hominoid based equations are most suited for Homo.
Collapse
Affiliation(s)
- Muhammad A Spocter
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown 2193, Johannesburg, South Africa.
| | | |
Collapse
|
92
|
Lust A, Fuller A, Maloney SK, Mitchell D, Mitchell G. Thermoregulation in pronghorn antelope (Antilocapra americanaOrd) in the summer. J Exp Biol 2007; 210:2444-52. [PMID: 17601948 DOI: 10.1242/jeb.005587] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARY
We have used thermistor/data logger assemblies to measure temperatures in the brain, carotid artery, jugular vein and abdominal cavity, and subcutaneously, in five pronghorn antelope over a summer in Wyoming. Globe and air temperature varied by up to ∼50°C daily during the summer and maximum solar radiation was ∼900 W m–2. Brain temperature(38.9±0.3°C) was consistently ∼0.2–0.5°C higher than carotid blood temperature (38.6±0.3°C), which was the same as abdominal temperature (38.8±0.4°C). Jugular blood temperature(38.0±0.4°C) varied, probably because of changes in Respiratory Evaporative Heat Loss (REHL), and was lower than other temperatures. Subcutaneous temperature (38.3±0.6°C) varied, probably because of peripheral vasoactivity, but on average was similar to other temperatures. Carotid blood temperature had a circadian/nycthemeral rhythm weakly but significantly (r=0.634) linked to the time of sunrise, of amplitude 0.8±0.1°C. There were daily variations of up to 2.3°C in carotid body temperature in individual animals. An average range of carotid blood temperature of 3.1±0.4°C over the study period was recorded for the group, which was significantly wider than the average variation in brain temperature (2.3±0.6°C). Minimum carotid temperature(36.4±0.8°C) was significantly lower than minimum brain temperature(37.7±0.5°C), but maximum brain and carotid temperatures were similar. Brain temperature was kept relatively constant by a combination of warming at low carotid temperatures and cooling at high carotid temperatures and so varied less than carotid temperature. This regulation of brain temperature may be the origin of the amplitude of the average variation in carotid temperature found, and may confer a survival advantage.
Collapse
Affiliation(s)
- A Lust
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA
| | | | | | | | | |
Collapse
|
93
|
Abstract
Why the extent of cortical gyrification varies across mammals of different brain sizes is a problem that is not clearly understood. The aim of the present study was to test a hypothesis indicating that the order is a significant phylogenetic grouping in terms of quantifiable gyrification indices (GIs) and thus variation between mammals. The GI was determined from serial sections of the brain of 25 different mammalian species, representing four different orders: primates, carnivores, ungulates and rodents. Image J analysis was used to measure the contours of the cerebral cortex, and the GI was calculated using three different methods of analysis: complete vs outer; gyral vs sulcal; and outer vs inner surface contours. The measurements were then computed against the brain weights of each species within the order. An increasing GI correlates with an increasing brain weight in all the mammalian orders. Each order has its own specific allometric pattern that is significantly different from the other orders. The ungulates were the mammals with the most gyrencephalic brains, these species being significantly more gyrencephalic than all other mammals when species of similar brain weights are compared. The North American beaver has an atypically lissencephalic brain for its size, differing from the trend for increased gyrencephaly found in the other rodent species examined. Our results show definite trends and patterns specific to each order; thus, it would seem that the order is a significant phylogenetic grouping in terms of this neural parameter, from which we can predict with a reasonable degree of certainty the GI of any species of a particular order given the brain weight.
Collapse
Affiliation(s)
- Praneshri Pillay
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, 7 York Road, Parktown, 2193, Johannesburg, Republic of South Africa
| | | |
Collapse
|
94
|
Abstract
A new study of contact calls in dolphins shows that individuals can recognize one another using information encoded in the frequency modulation pattern of these calls, in the absence of general voice characteristics.
Collapse
Affiliation(s)
- Robert A Barton
- Evolutionary Anthropology Research Group, Durham University, Durham DH1 3HN, UK.
| |
Collapse
|