Neurobiology of monotremes : brain evolution in our distant mammalian cousins PDF
Preview Neurobiology of monotremes : brain evolution in our distant mammalian cousins
N E U R O B I The monotremes are an unusual and evolutionarily important group O of mammals showing striking behavioural and physiological L adaptations to their niches. They are the only mammals exhibiting O electroreception (in the trigeminal sensory pathways) and the echidna About the editor shows distinctive olfactory specialisations. This book brings together Ken Ashwell has over 33 years’ G experience in the neurosciences. He has current information on the development, structure, function and Y published over 110 papers in international behavioural ecology of the monotremes. refereed journals, 23 book chapters and O six books. He has also published four NEUROBIOLOGY Neurobiology of Monotremes aims to close the current gap in atlases in collaboration with George F knowledge between the genes and developmental biology of Paxinos and contributed many chapters to prestigious and defi nitive works on the M monotremes on the one hand, and the adult structure, function and structure, function and development of ecology of monotremes on the other. It explores how the sequence O OF MONOTREMES the human and mouse nervous systems. ‘embryonic structure > adult structure > behaviour’ is achieved He has published over 50 major works N (papers, books, book chapters) on in monotremes and how this differs from other mammals. The work comparative neuroscience of Australasian O also combines a detailed review of the neurobiology of monotremes mammals and birds; 26 of these have Brain Evolution in Our Distant with photographic and diagrammatic atlases of the sectioned adult been on monotreme neuroscience and T brains and peripheral nervous system of the short-beaked echidna 26 on marsupial neuroscience. R Mammalian Cousins and platypus. Pairing of a detailed review of the fi eld with the fi rst E published brain atlases of two of the three living monotremes will allow M the reader to immediately relate key points in the text to features in E the atlases and will extend a universal system of brain nomenclature S developed in eutherian brain atlases by George Paxinos and colleagues to monotremes. ASHWELL Editor: Ken Ashwell Neurobiology of Monotremes Final.indd 1 27/08/13 9:38 AM Neurobiology of MoNotreMes To Mark Joseph Rowe 1943–2011 Friend, colleague and mentor Neurobiology of MoNotreMes Brain Evolution in Our Distant Mammalian Cousins Editor: Ken Ashwell © Ken Ashwell 2013 All rights reserved. Except under the conditions described in the Australian Copyright Act 1968 and subsequent amend- ments, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, duplicating or otherwise, without the prior permission of the copyright owner. Contact CSIRO PUBLISHING for all permission requests. National Library of Australia Cataloguing-in-Publication entry Ashwell, Ken W. S., editor. Neurobiology of monotremes : brain evolution in our distant mammalian cousins / edited by Ken Ashwell. 9780643103115 (hardback) 9780643103153 (epdf) 9780643103160 (epub) Includes bibliographical references and index. Monotremes. Neurobiology. Neuroanatomy. Neurophysiology. Ashwell, Ken W. S., editor. 599.1 Published by CSIRO PUBLISHING 150 Oxford Street (PO Box 1139) Collingwood VIC 3066 Australia Telephone: +61 3 9662 7666 Local call: 1300 788 000 (Australia only) Fax: +61 3 9662 7555 Email: [email protected] Website: www.publish.csiro.au Front cover and title page: illustrations by Anne Musser Set in 10/13 Palatino Edited by Joy Window Cover and text design by James Kelly Typeset by Thomson Digital Printed in China by 1010 Printing International Ltd CSIRO PUBLISHING publishes and distributes scientific, technical and health science books, magazines and journals from Australia to a worldwide audience and conducts these activities autonomously from the research activities of the Common- wealth Scientific and Industrial Research Organisation (CSIRO). The views expressed in this publication are those of the author(s) and do not necessarily represent those of, and should not be attributed to, the publisher or CSIRO. The copyright owner shall not be liable for technical or other errors or omissions contained herein. The reader/user accepts all risks and responsibility for losses, damages, costs and other consequences resulting directly or indirectly from using this information. Original print edition: The paper this book is printed on is in accordance with the rules of the Forest Stewardship Council®. The FSC® promotes environmentally responsible, socially beneficial and eco- nomically viable management of the world’s forests. Contents List of contributors vii Preface ix Acknowledgements xi 1 Classification and evolution of the monotremes 1 A. M. Musser 2 Behaviour and ecology of monotremes 17 Stewart C. Nicol 3 embryology and post-hatching development of the monotremes 31 Ken W. S. Ashwell 4 overview of monotreme nervous system structure and evolution 47 Ken W. S. Ashwell 5 Peripheral nervous system, spinal cord, brainstem and cerebellum 69 Ken W. S. Ashwell 6 Diencephalon and deep telencephalic structures 107 Ken W. S. Ashwell 7 Cerebral cortex and claustrum/endopiriform complex 131 Ken W. S. Ashwell 8 Visual system 161 Ken W. S. Ashwell 9 somatosensory and electrosensory systems 179 Ken W. S. Ashwell and Craig D. Hardman 10 Auditory and vestibular systems 219 Ken W. S. Ashwell 11 Chemical senses: olfactory and gustatory systems 235 Ken W. S. Ashwell vi NeurobioLogy of MoNotreMes 12 the hypothalamus, neuroendocrine interface and autonomic regulation 251 Ken W. S. Ashwell 13 Monotremes and the evolution of sleep 275 Ken W. S. Ashwell 14 Reflections: monotreme neurobiology in context 285 Ken W. S. Ashwell 15 Atlas and tables of peripheral nervous system anatomy 299 Ken W. S. Ashwell and Anne M. Musser 16 Atlas of the adult and developing brain and spinal cord of the short-beaked echidna (Tachyglossus aculeatus aculeatus) 315 Ken W. S. Ashwell and Craig D. Hardman 17 Atlas of the adult and developing brain of the platypus (Ornithorhynchus anatinus) 387 Ken W. S. Ashwell and Craig D. Hardman List of abbreviations used in brain and embryo atlas plates 437 Index of brain and embryo atlas plates 447 References 465 Glossary 495 Appendix tables and figures 505 Index 515 LIst of ContRIButoRs Ken W. S. Ashwell Department of Anatomy, School of Medical Sci- ences, University of New South Wales Craig D. Hardman Department of Anatomy, School of Medical Sci- ences, University of New South Wales A. M. Musser Australian Museum, Sydney Stewart C. Nicol School of Zoology, University of Tasmania This page intentionally left blank PRefACe What is the place of the modern monotremes in mam- earlier studies, the pendulum of scientific opinion has malian brain evolution? For many years during the perhaps swung too far, in that electroreception is now 19th and 20th century they were seen as quaint rem- seen almost as the defining and characteristic sen- nants of the ancestral mammalian condition, indica- sory modality of the modern monotremes, at the tive of the original state of the mammalian body plan. expense of olfaction and general somato- or touch The platypus was seen as a bizarre, almost chimeric, sensation in the head, trunk and limbs. Electrorecep- pastiche of features familiar from Northern Hemi- tion has taken on almost mythic stature in the popu- sphere mammals, while the short-beaked echidna lar scientific literature, so much so that the story of was viewed as a shambling, animated pincushion. the clever platypus navigating its stream bed habitat Adjectives such as ‘prototypical’ and ‘primitive’ were using nothing more than an uncanny sense for elec- often used in the neuroscience literature in associa- trical fields is familiar to every Australian school tion with both the platypus and echidnas. It was felt child. These cute and cosy wildlife stories ignore the that if we could understand the nervous systems of fact that most of the prey of the platypus emit little or these supposedly ‘archaic’, ‘archetypal’, ‘ancient’, ‘pre- no electrical signals and that the evidence for field historic’ and ‘primordial’ mammals, then we would navigation with electroreception in the wild is non- be able to glean clues not just as to how the first mam- existent. The evidence for use of electroreception by malian brains were built and worked, but how the echidnas in the natural setting is even weaker. brains of so-called advanced mammals (i.e. primates The focus on electroreception has also strongly and of course humans) subsequently evolved. influenced conceptions of monotreme evolutionary Far from being primitive mammals, the modern history, with several authors maintaining that the monotremes are extraordinarily successful creatures earliest monotremes were electroreceptive and essen- with remarkable adaptations to their environment. tially platypus-like in both morphology and habits. Certainly the monotremes have many anatomical fea- As will be argued in this book, this contention flies in tures in common with extinct primitive mammals, the face of the embryological evidence and is founded but then so do humans (look at your own primitive on a logical flaw, i.e. the absence of fossil evidence to and generalised forelimb). Any modern creature is a the contrary. As such, the platypus first hypothesis is a mosaic of primitive and advanced characteristics. misconception that arises from the patchy tachyglos- Primitive features are inherited unchanged from a sid fossil record. distant ancestor, simply because those features served I hope that the reader will come to share some- their purpose well enough in the competition for sur- thing of the fascination that I feel for the remarkable vival, whereas advanced features or specialisations monotremes and their extraordinary nervous sys- are critically important for continued existence and tems and behaviour. In the absence of a complete have been relentlessly honed for their purpose by fossil record, we can only indirectly infer much of natural selection. their neural evolution. Nevertheless, the modern The remarkable specialisations of the living monotremes are critically important animals for monotremes are nowhere more evident than in their understanding mammalian brain evolution, not nervous systems. The discovery of mammalian elec- because they are primitive living fossils, but because troreception in, first, the platypus and then the short- their story tells a tale of ancient origins and astonish- beaked echidna highlighted the highly specialised ing sensory adaptations to their environment. nature of the monotreme nervous system. Although a welcome improvement over the chauvinistic bias of Ken Ashwell
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