Invertebrates SECOND EDITION Richard C. Brusca Director of Conservation and Science, Arizona-Sonora Desert Museum Gary J. Brusca Late, Professor of Zoology, Humboldt State University with illustrations by Nancy Haver Sinauer Associates, Inc., Publishers Sunderland, Massachusetts 01375 © Sinauer Associates, Inc. This material cannot be copied, reproduced, manufactured or disseminated in any form without express written permission from the publisher. Brief Contents 1 Introduction 1 2 Classification, Systematics, and Phylogeny 23 3 Animal Architecture and the Bauplan Concept 41 4 Animal Development, Life Histories, and Origins 93 5 The Protists 121 6 Phylum Porifera: The Sponges 179 7 Four Phyla of Uncertain Affinity 209 8 Phylum Cnidaria 219 9 Phylum Ctenophora: The Comb Jellies 269 10 Phylum Platyhelminthes 285 11 Phylum Nemertea: The Ribbon Worms 319 12 Blastocoelomates and Other Phyla 337 13 Phylum Annelida: The Segmented Worms 389 14 Sipuncula and Echiura 447 15 The Emergence of the Arthropods: Onychophorans, Tardigrades, Trilobites, and the Arthropod Bauplan 463 16 Phylum Arthropoda: The Crustacea 513 17 Phylum Arthropoda: The Hexapoda (Insects and Their Kin) 591 18 Phylum Arthropoda: The Myriapods (Centipedes, Millipedes, and Their Kin) 639 19 Phylum Arthropoda: The Cheliceriformes 655 20 Phylum Mollusca 703 21 Lophophorates 773 22 Phylum Echinodermata 803 23 Other Deuterostomes: Chaetognatha, Hemichordata, Chordata 841 24 Perspectives on Invertebrate Phylogeny 875 © Sinauer Associates, Inc. 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Contents Preface xvii Acknowledgments xix 1 Introduction 1 Where Did Invertebrates Come From? 4 Freshwater Habitats 13 The Dawn of Life 4 Terrestrial Habitats 14 The Ediacaran Epoch and the Origin of Animals 5 A Special Type of Environment: Symbiosis 14 The Paleozoic Era (570–250 mya) 6 Some Comments On Evolution 15 The Mesozoic Era (250–65 mya) 7 Microevolution 15 The Cenozoic Era (65 mya–present) 7 Macroevolution 16 Where Do Invertebrates Live? 9 A Final Introductory Message to the Reader Marine Habitats 9 19 Estuaries and Coastal Marshlands 13 2 Classification, Systematics, and Phylogeny 23 Biological Classification 24 Important Concepts and Terms 28 Nomenclature 24 Constructing Phylogenies and Classifications Systematics 27 31 3 Animal Architecture and the Bauplan Concept 41 Body Symmetry 43 Feeding Strategies 57 Cellularity, Body Size, Germ Layers, and Excretion and Osmoregulation 66 Body Cavities 46 Nitrogenous Wastes and Water Conservation 66 Locomotion and Support 49 Osmoregulation and Habitat 67 Ameboid Locomotion 50 Excretory and Osmoregulatory Structures 68 Cilia and Flagella 50 Circulation and Gas Exchange 71 Muscles and Skeletons 52 Internal Transport 71 Feeding Mechanisms 56 Circulatory Systems 71 Intracellular and Extracellular Digestion 56 Hearts and Other Pumping Mechanisms 73 © Sinauer Associates, Inc. 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VIII CONTENTS Gas Exchange and Transport 73 Nervous Systems and Sense Organs 77 Invertebrate Sense Organs 77 Sense Organs 78 Independent Effectors 82 Bioluminescence 82 Nervous Systems and Body Plans 82 Hormones and Pheromones 84 Reproduction 84 Asexual Reproduction 85 Sexual Reproduction 86 Parthenogenesis 88 4 Animal Development, Life Histories, and Origins 93 Eggs and Embryos 93 Mixed Development 105 Eggs 94 Adaptations to Land and Fresh Water 106 Cleavage 94 Parasite Life Cycles 106 The Problem of Cell Fates 98 The Relationships between Ontogeny and Blastula Types 98 Phylogeny 106 Gastrulation and Germ Layer Formation 99 The Concept of Recapitulation 107 Mesoderm and Body Cavities 100 Heterochrony and Paedomorphosis 108 Life Cycles: Sequences and Strategies 102 Origins of Major Groups of Metazoa 108 Classification of Life Cycles 102 Origin of the Metazoa 108 Indirect Development 103 Origin of the Bilateral Condition 112 Settling and Metamorphosis 104 Origin of the Coelomic Condition 112 Direct Development 105 5 The Protists 121 Taxonomic History and Classification 123 Reproduction and Life Cycles 135 Classification of the Protista 123 Phylum Ciliophora (The Ciliates) 135 The Protist Bauplan 124 Support and Locomotion 135 Body Structure, Excretion, and Gas Exchange 124 Nutrition 139 Support and Locomotion 125 Reproduction 142 Nutrition 125 Phylum Apicomplexa (The Gregarines, Activity and Sensitivity 125 Coccidians, Haemosporidians, and Reproduction 127 Piroplasms) 145 Phylum Euglenida 129 Support and Locomotion 146 Support and Locomotion 130 Nutrition 146 Nutrition 131 Reproduction and Life Cycles 147 Reproduction 131 Phylum Dinoflagellata 148 Phylum Kinetoplastida (The Trypanosomes Support and Locomotion 151 and Their Relatives) 131 Nutrition 151 Support and Locomotion 133 Reproduction 152 Nutrition 134 © Sinauer Associates, Inc. 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CONTENTS IX Phylum Stramenopila 153 Phylum Diplomonadida 167 Support and Locomotion 154 Support and Locomotion 168 Nutrition 154 Nutrition 169 Reproduction 155 Reproduction 169 Phylum Rhizopoda (Amebas) 155 Phylum Parabasilida (The Trichomonads Support and Locomotion 157 and Hypermastigotes) 169 Nutrition 159 Support and Locomotion 170 Reproduction 160 Nutrition 171 Phylum Actinopoda 161 Reproduction 171 Support and Locomotion 162 Phylum Cryptomonada 172 Nutrition 163 Phylum Microspora 172 Reproduction 164 Phylum Ascetospora 173 Phylum Granuloreticulosa (Foraminifera and Phylum Choanoflagellata 173 Their Kin) 165 Phylum Chlorophyta 173 Support and Locomotion 166 Nutrition 166 Phylum Opalinida 173 Reproduction and Some Life Cycles 167 Genus Stephanopogon 174 Protist Phylogeny 174 6 Phylum Porifera: The Sponges 179 Taxonomic History and Classification 180 Growth Rates 202 The Poriferan Bauplan 182 Symbioses 202 Body Structure and the Aquiferous System 183 Poriferan Phylogeny 203 Cell Types 188 The Origin of Sponges 203 Cell Aggregation 191 Evolution within the Porifera 204 Support 191 Nutrition, Excretion, and Gas Exchange 192 Activity and Sensitivity 194 Reproduction and Development 196 Some Additional Aspects of Sponge Biology 201 Distribution and Ecology 201 Biochemical Agents 201 7 Four Phyla of Uncertain Affinity 209 Taxonomic History 209 Phylum Rhombozoa 211 Mesozoan Bauplans 210 Phylum Orthonectida 215 Phylum Placozoa 210 Mesozoan Phylogeny 216 Phylum Monoblastozoa 210 © Sinauer Associates, Inc. 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X CONTENTS 8 Phylum Cnidaria 219 The Body Wall 226 Support 236 Movement 239 Cnidae 242 Feeding and Digestion 244 Defense, Interactions, and Symbiosis 246 Circulation, Gas Exchange, Excretion, and Osmoregulation 250 Nervous System and Sense Organs 250 Reproduction and Development 253 Cnidarian Phylogeny 261 Taxonomic History and Classification 222 The Cnidarian Bauplan 225 9 Phylum Ctenophora: The Comb Jellies 269 Taxonomic History and Classification 271 Circulation, Excretion, Gas Exchange, and The Ctenophoran Bauplan 274 Osmoregulation 279 Nervous System and Sense Organs 279 Support and Locomotion 274 Reproduction and Development 280 Feeding and Digestion 276 Ctenophoran Phylogeny 281 10 Phylum Platyhelminthes 285 Taxonomic History and Classification 286 Circulation and Gas Exchange 299 The Platyhelminth Bauplan 289 Excretion and Osmoregulation 299 Body Wall 291 Nervous System and Sense Organs 300 Support, Locomotion, and Attachment 294 Reproduction and Development 303 Feeding and Digestion 295 Platyhelminth Phylogeny 313 11 Phylum Nemertea: The Ribbon Worms 319 Taxonomic History and Classification 321 Circulation and Gas Exchange 327 Classification 321 Excretion and Osmoregulation 328 The Nemertean Bauplan 322 Nervous System and Sense Organs 329 Body Wall 322 Reproduction and Development 331 Support and Locomotion 322 Nemertean Phylogeny 333 Feeding and Digestion 323 © Sinauer Associates, Inc. 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CONTENTS XI 12 Blastocoelomates and Other Phyla 337 Taxonomic History 338 Phylum Priapula: The Blastocoelomate Condition 338 The Priapulans 365 Phylum Rotifera: Body Wall, Support, and Locomotion 367 The Rotifers 338 Feeding and Digestion 367 General External Anatomy and Details of the Circulation, Gas Exchange, Excretion, and Corona 340 Osmoregulation 368 Body Wall, Body Cavity, Support, and Locomotion Nervous System and Sense Organs 368 341 Reproduction and Development 368 Feeding and Digestion 341 Phylum Acanthocephala: Circulation, Gas Exchange, Excretion, and The Acanthocephalans 368 Osmoregulation 343 Body Wall, Support, Attachment, and Nutrition Nervous System and Sense Organs 343 369 Reproduction and Development 343 Circulation, Gas Exchange, and Excretion 370 Phylum Gastrotricha: Nervous System 370 The Gastrotrichs 345 Reproduction and Development 370 Body Wall, Support, and Locomotion 346 Phylum Entoprocta: Feeding and Digestion 347 The Entoprocts 371 Circulation, Gas Exchange, Excretion, and Body Wall, Support, and Movement 373 Osmoregulation 347 Feeding and Digestion 373 Nervous System and Sense Organs 347 Circulation, Gas Exchange, and Excretion 374 Reproduction and Development 347 Nervous System