Evolutionary Developmental Biology of Invertebrates 1 : Introduction, Non-Bilateria, Acoelomorpha, Xenoturbellida, Chaetognatha

This multi-author, six-volume work summarizes our current knowledge on the developmental biology of all major invertebrate animal phyla. The main aspects of cleavage, embryogenesis, organogenesis and gene expression are discussed in an evolutionary framework. Each chapter presents an in-depth yet concise overview of both classical and recent literature, supplemented by numerous color illustrations and micrographs of a given animal group. The largely taxon-based chapters are supplemented by essays on topical aspects relevant to modern-day EvoDevo research such as regeneration, embryos in the fossil record, homology in the age of genomics and the role of EvoDevo in the context of reconstructing evolutionary and phylogenetic scenarios. A list of open questions at the end of each chapter may serve as a source of inspiration for the next generation of EvoDevo scientists. __Evolutionary Developmental Biology of Invertebrates__ is a must-have for any scientist, teacher or student interested in developmental and evolutionary biology as well as in general invertebrate zoology. This volume starts off with three chapters that set the stage for the entire work by covering general aspects of EvoDevo research, including its relevance for animal phylogeny, homology issues in the age of developmental genomics, and embryological data in the fossil record. These are followed by taxon-based chapters on the animals that are commonly considered to have branched off the Animal Tree of Life before the evolution of the Bilateria: the Porifera, Placozoa, Cnidaria (with the Myxozoa being treated separately) and Ctenophora. In addition, the Acoelomorpha, Xenoturbellida and Chaetognatha are examined, including their currently hotly debated phylogenetic affinities. Preface 6 Contents 8 1: EvoDevo and Its Significance for Animal Evolution and Phylogeny 9 Ontogeny vs Phylogeny 10 Evolutionary Developmental Biology 10 Recapitulation vs Cladistic Assessments of Character Polarity 11 Developmental Genes and Phylogenetic Inference 12 Gene-Based Homology 12 The Genotype→Phenotype Map 12 Convergence 12 From Gene Phylogeny to a Comparison of Gene Expression Patterns 13 miRNA and Phylogeny 14 Conservation of Gene Function and Developmental System Drift 14 Evolving Gene Functions 14 Gene Regulatory Networks and Their Evolution 15 Gene Loss and Character Loss 16 Gene and Gene Network Co-option vs Paramorphism 17 Segmentation: Genes and Bilaterian Phylogeny 18 Rethinking Embryological Evidence of Phylogenetic Relationships 19 The Phylogenetic Signal of Cleavage Patterns 19 Germ Layer Homology 19 Primary vs Secondary Larvae 20 Tempo and Mode in Evolution 21 Heterochrony in Phylogenetics: Noise or Data? 21 Growth Heterochrony vs Sequence Heterochrony 22 Hot Points of Change Along the Developmental Schedule 22 Saltational Evolution and Discontinuous Variation 23 References 24 2: Homology in the Age of Developmental Genomics 32 Introduction 33 Challenges 34 Individuality 35 Character Identity and Character States 36 Homology Is a Narrower Concept Than Apomorphy 36 The Genetic Basis of Character Identity 38 Character Modalities 40 Characterization of Character Identity Networks 42 The Experimental Study of Character Identity 43 Technical Issues in the Use of Transcriptomes for the Study of Innovation 45 Gene Regulatory Network Reconstruction 47 Coda 48 References 48 3: Embryology in Deep Time 51 Introduction 51 Disinterring the Biology of Fossil Embryos 52 Ontogeny and Taphonomy 54 Fossil Invertebrate Embryos 56 Markuelia 56 Olivooides and Quadrapyrgites 58 Pseudooides 60 Tianzhushania 61 Spiralicellula and Helicoforamina 64 Other Candidate Embryos from the Doushantuo Biota 64 Other Records of Fossil Embryos 65 The Nature of the Fossil Record of Embryos 65 References 66 4: Porifera 70 Introduction 71 Phylogenetic Position of Porifera 71 Phylogenetic Relationships of Poriferan Classes 73 Developmental Commonalities Within the Porifera 73 The Demosponge Amphimedon queenslandica and the Calcareous Sponge Sycon ciliatum 75 The Amphimedon queenslandica Brood Chamber: Gametogenesis and Fertilisation 77 Early Embryonic Development in Amphimedon queenslandica 79 Cleavage 79 Asymmetric Cell Division and Transcript Localisation 82 Cell Layer Formation and Establishment of Axial Polarity 87 Localisation of Wnt and TGF-β Transcripts in the Early Embryo 88 Late Embryonic Development in Amphimedon queenslandica 91 Spot Stage and Commencement of Larval Tissue Formation 91 Pigment Ring Formation 92 Autonomous Formation of Pigment Spots and Rings 96 Localised and Cell Type-Specific Gene Expression in Late Stage Embryos and Larvae 96 Localised Expression of Conserved Developmental Genes During Pigment Ring Formation 99 Settlement and Metamorphosis in Amphimedon queenslandica 99 The Calcareous Sponge Sycon ciliatum 102 Sycon ciliatum Development 105 Open Questions 108 References 108 5: Placozoa 112 Introduction 113 Sexual Reproduction 114 Oogenesis 114 Spermatogenesis 116 Early Embryonic Development 116 Vegetative Reproduction 116 Developmental Genes 117 Open Questions 118 References 118 6: Cnidaria 120 Introduction 121 General Aspects of Cnidarian Early Development 125 General Aspects of Cnidarian Late Development 125 General Questions of Development and Body Plan Evolution 125 Medusozoan Model Systems 126 Hydra 126 Hydra Gametogenesis and Embryonic Development 127 The Head Organizer and Axis Formation 129 Interstitial Stem Cell in Hydra: Maintenance and Differentiation 134 Hydractinia echinata and Hydractinia symbilongicarpus 138 Podocoryne carnea 141 Clytia hemisphaerica 141 Aurelia aurita and Tripedalia sp. 145 Anthozoans 148 Acropora spec 148 Nematostella vectensis 150 Molecular Tools and Genomic Features 150 Normal Development 152 Germ Layer Formation and the Evolution of the Mesoderm 155 Axis Formation: The Role of Wnt and BMP Signaling 155 Hox Genes 156 The Development of the Nervous System 157 Beyond Development: Cnidarians and the Environment 158 Concluding Remarks: Cnidarian and Bilaterian EvoDevo 159 Open Questions 160 References 160 7: Myxozoa 169 Introduction 170 Development 174 Development in the Invertebrate Host 174 Malacosporea 174 Myxosporea 176 Development in the Vertebrate Host 177 Malacosporea 177 Myxosporea 178 Experimental and Gene Expression Studies 178 Open Questions 179 References 179 8: Ctenophora 182 Introduction 183 Early Development 186 Ctenophore Fate Mapping 189 Experimental Embryology 191 The Role of the Cleavage Program in the Establishment of Spatial Organization 192 Late Development 193 Adult Regeneration 193 Evidence for Quadrant-Specific Positional Information 194 Post-generation 194 Dissogeny 196 Gene Expression 197 Open Questions 201 References 201 9: Acoelomorpha and Xenoturbellida 205 Introduction 206 Development of Xenoturbellida 206 Development of Acoelomorpha 207 Acoela 209 Cleavage 209 Gastrulation 211 Organogenesis 211 Postembryonic Development 212 Molecular Approaches 212 Nemertodermatida 214 Open Questions 214 References 214 10: Chaetognatha 217 Introduction 218 Early Development 221 Germ Plasm, Primary Germ Cells, and Fertilisation 221 Cleavage and Gastrulation 224 Chaetognath Gastrulation in the Light of Their Presumed Phylogenetic Position 227 Late Development 228 Ontogeny of Mesoderm-Derived Tissues and Organisation of the Internal Body Cavities: Are Chaetognaths Bipartite Animals? 228 Neurogenesis 234 Gene Expression 238 Open Questions 239 References 239 Index 243 Front Matter....Pages i-vii EvoDevo and Its Significance for Animal Evolution and Phylogeny....Pages 1-23 Homology in the Age of Developmental Genomics....Pages 25-43 Embryology in Deep Time....Pages 45-63 Porifera....Pages 65-106 Placozoa....Pages 107-114 Cnidaria....Pages 115-163 Myxozoa....Pages 165-177 Ctenophora....Pages 179-201 Acoelomorpha and Xenoturbellida....Pages 203-214 Chaetognatha....Pages 215-240 Back Matter....Pages 241-251