By Alessandro Minelli Cambridge University Press, 2003 FROM THE BACK COVER Contemporary research in the field of evolutionary developmental biology, or 'evo-devo', has to date been predominantly devoted to interpreting basic features of animal architecture in molecular genetics terms. Considerably less time has been spent on the exploitation of the wealth of facts and concepts available from traditional disciplines, such as comparative morphology, even though these traditional approaches can continue to offer a fresh insight into evolutionary developmental questions. The Development of Animal Form aims to integrate traditional morphological and contemporary molecular genetic approaches and to deal with postembryonic development as well. This approach leads to unconventional views on the basic features of animal organization, such as body axes, symmetry, segments, body regions, appendages and related concepts. This book will be of particular interest to graduate students and researchers in evolutionary and developmental biology, as well as to those in related areas of cell biology, genetics and zoology. Alessandro Minelli is a Professor of Zoology at the University of Padova, Italy. An honorary fellow of the Royal Entomological Society, he was a founding member and vice-president of the European Society for Evolutionary Biology. From 1995 to 2001, he served as president of the International Commission on Zoological Nomenclature. He served on the editorial board of multiple learned journals, including Evolution & Development. TABLE OF CONTENTS Preface xiii Acknowledgements xvii 1. The Nature of Development 1 Development for the Sake of Development 1 Developmental Competition between Body Parts 7 The Robustness of Morphogenesis 9 2. Everything Begun to the Service of Development: Cellular Darwinism and the Origin of Animal Form 12 Cilia, Cell Division, and Morphogenesis 12 Epithelia without Cilia 12 Origin of the Ecdysozoan Cuticle 13 Cuticle, Body Size, and Internal Fertilisation 16 Origin of Mineralised Skeletons 18 Organic Matrices 19 Coda 19 3. Development: Generic to Genetic 21 Developmental Genes 21 Master Control Genes? 25 Self-Assembly or Cytotaxis? 27 Default Morphology 30 Generic Forms 32 A Bestiary of Generic Forms 35 The Earthworm and the Ankylosaurus 36 Deceptive Numbers 38 Genetic Assimilation 39 Genes and Phenotype 41 Evolutionary Dissociation between Genes and Phenotypes 42 A Role for the 'Developmental Genes' 44 The Hox Code 44 Organic Codes 50 Universal Genetic Tools 51 Genetic Networks and Morphogenesis 53 4. Periodisation 55 The Primacy of Time 56 Time Schedule: Synchronous Versus Metachronous 57 Units in Time 57 Homology of Developmental Stages or Events 58 Comparing Stages 60 What Is a Larva? 65 Metamorphosis as Metagenesis 67 Postembryonic Development 67 One Life throughout the Metamorphosis 67 Developmental Stages as Units of Competition? 68 The Evolution of Moulting Schedules in the Ecdysozoa 71 Number of Moults, Dyar's Coefficient, and Targeted Growth 73 Lazarus Developmental Features 75 Recapitulation 77 5. Body Regions: Their Boundaries and Complexity 79 Tagmosis 79 Instability of Tagmatic Boundaries 83 Homology of Tagmata 85 Number of Tagmata and Convergence 86 The Complexity of Postembryonic Development 88 Williston's Rule 92 Developmental Time and Body Axes 92 The Time Axis of Development and the Patterning of the Proximo-Distal Axis of the Appendages 97 Topology 99 Morphology and Developmental Topology 99 Topology of Coaptations 102 Topological Breakdown 104 6. Differentiation and Patterning 106 Cells as Units of Differentiation 106 Cell Cycle Length 108 Cell Types 109 Cell Autonomy, Induction, and Repatterning 109 Cell Contacts and Cell Communication 110 Asymmetric Cell Divisions 111 Positional Homology and the Hot Spots of Differentiation 111 Positional Information or Informational Position? 111 Zootype and the Patterning of the Nervous System 112 Cellularity and Positional Information 115 Transpatterning 116 Provisional Scaffolding 116 Segments, Vertebrae, and Scales 119 Guidelines to Follow 121 Phylotypic Stage and Phylotypic Period 123 Morphological Assimilation in Ontogeny and Phylogeny 127 Patterning in Regeneration 130 Embryonic Patterning Versus Patterning in Regeneration 130 Terminal or Apical Control Versus Regeneration 131 7. Size Factors 133 Cell Size Critical for Morphogenesis 133 Size and Cell Number in Embryonic Anlagen 135 Early Because Small or Small Because Early? 135 Critical Number of Cells in Embryonic Anlagen 137 Miniaturisation 139 Miniaturisation and Body Patterning 139 Miniaturisation, Segments, and Cells 140 8. Axes and Symmetries 142 The Animal's Main Body Axis 142 Polyps, Sipunculans, and Squids 143 The Dual Animal 147 Sipunculans and ParaHox Genes 149 Morphological Versus Functional Polarity 150 Cartesian Axes, or Not 152 The Syntax of the Body What Is a Tail? 155 The Time Arrow of Growth and Differentiation 158 The Beginnings of Animal Polarity 159 Tapeworm Polarity 160 Differentiating Back to Front 162 Polarity Reversal 163 Axis Paramorphism and Origin of the Appendages 163 Axis Paramorphism 164 Terminal Control and Axis Paramorphism 173 Gene Co-option 175 Limbs and Genitalia 176 Symmetry and Asymmetry 182 Directional Asymmetry 185 9. Segments 188 What Is a Segment? 188 Virtual Versus Physical Segmental Boundaries 190 How Many Times Did Metazoans Evolve Segmentation? 192 Reconstructing Urbilateria 193 Segments in Annelids, Arthropods, and Vertebrates 195 Limits of a Typological View of Segments 197 Segmentation: One Animal, More than One Mechanism 200 Double Segmentation: Eosegments and Merosegments 200 The Naupliar-Postnaupliar-Meromeric Model of Arthropod Segmentation 204 Reliable Patterning of Eosegments and the Variable Schedule of Merosegmentation 209 Heterogeneous Segments in Vertebrates and Annelids 212 Germ Layers and Segmentation 215 Segmental Mismatches and Resegmentation 216 Dorso-Ventral Mismatches 216 Resegmentation 219 10. Evo-devo Perspectives on Homology 222 Concepts and Interpretations 222 Hierarchies and Beyond 222 Homology: Absolute or Relative? 223 Temporal Serial Homology 227 Genes and Homology 228 Genetic Redundancy, Network Degeneracy, and Homology 231 Evolutionary Novelties 232 Units of Description and Comparison 233 Modules 234 Evolutionary Changes in the Discernibility of Developmental Modules: Fusion Versus Non-disjunction 235 Germ Layers and Homology 236 Lesser Developmental Units 241 Frames of Reference: Muscles and Nerves 243 Muscles and Homology 244 Nerves and Homology 247 Summaries and Conclusions 250 References 255 Index 313 WHERE TO ORDER: Cambridge University Press 110 Midland Avenue Port Chester, NY 10573-4930 General phone: (914)937-9600 General fax: (914)937-4712 www.us.cambridge.org ISBN: 0521808510 (hardcover) $75.00 USD Posted Date: 6/12/2003
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