The Atlas of Comparative Invertebrate Embryology has two aims. Firstly, it describes embryonic development or ontogeny of several species within a phylum. Secondly, by comparing the different ontogenies this collection supplies a basis for phylogenetic reflections about phylum-level relationships in lower Metazoa. Diversity of ontogenies, embryos and larvae can be an important source for well-founded phylogenetic theories. Like comparative morphology and anatomy, comparative embryology plays a central role for the analysis of evolution.
The Atlas of Comparative Invertebrate Embryology presents a wealth of embryonic and larval developmental processes to emphasize the great variety of ontogenies in the animal kingdom. Like the adult organisms, larvae are also of an enormous diversity owing to the varied requirements of their environment. Within a phylum, embryonic and larval development may be uniform to a large degree, but also deviations are known. In comparing the different ontogenies of an animal phylum, embryologists try to find out the common ancestor and to reconstruct the phylogeny of the group.
Establishing a phylogenetic system of the animal kingdom on the basis of comparative embryology requires a sound theory to integrate far reaching steps in evolution of the animal phyla. Two theories, which are founded in simple events that equally occur in many embryonic developmental courses of different phyla, are the Gastraea–theory of Haeckel (1874) and the Archicoelomata–theory of Masterman (1898). In the Atlas of Comparative Invertebrate Embryology, the phylogenetic system proposed by comparison of the different ontogenies is based on these two theories.
The atlas offers a broad view about the diversity of embryos and larvae and may be useful in looking for a suitable species of special interest. Naturally, an exhaustive description of all ontogenies of animals is impossible. Ontogenies of well known species and detailed research work of their embryos have been chosen. Besides this, embryological research work of some Metazoan phyla is incomplete. Our knowledge of the ontogeny of animals is mainly founded on the classical investigations between 1860 and 1960. In the Atlas of Comparative Invertebrate Embryology, in the chapters concerning phylogenetic interrelationships of phyla, results of studies on morphological or biochemical composition of structures of the adults and of modern gene sequence data may be included into discussion.
Phylum Lophophorata 8
Class Phoronida 8
Phoronis buskii (McINTOSH) 9
Phoronis muelleri (de SELYS-LONGCHAMPS) 15
Phoronis psammophila (CORI) 19
Phoronis vancouverensis (PIXELL) 23
Phoronis ovalis (S. WRIGHT) 25
Phoronopsis harmeri (PIXELL) 27
Summary of Embryonic Development in Phoronida 30
Fertilization, cleavage and gastrulation 30
Mesoderm formation in larva 30
Larva 31
Metamorphosis 32
Embryonic development in Phoronida 32
Class- and phylum-level relationships of Phoronida 33
Prosoma 33
Mesosoma 34
Metasoma 34
Nervous system of the actinotrocha 35
Ciliary bands 35
Literature 36
Class Brachiopoda 38
Ecardines 39
Lingula unguis (LINNÉ) 39
Glottidia pyramidata (STIMPSON) 41
Discinisca strigata (BRODERIP) 44
Discinisca atlantica (KING) 46
Crania anomala (O. F. MÜLLER) 48
Testicardines 52
Notosaria nigrcans (SOWERBY) 52
Terebratulina septentrionalis (COUTHOUY) 55
Terebratulina retusa (LINNÉ) 60
Argyrotheca cordata (RISSO) 63
Waltonia inconspicua (SOWERBY) 65
Pumilus antiquatus (ATKINS) 68
Terebratalia transversa (SOWERBY) 70
Summary of Embryonic Development in Brachiopoda 73
Embryonic development 73
Larval development in Testicardines 73
Juvenile development in Ecardines: Lingula, Glottidia, and Discinisca 74
Larval development in Ecardines: Crania 75
Adult morphology, embryonic and larval development in Brachiopoda and evolutionary interpretation 75
Morphology 75
Embryology 76
Larvae and juveniles 76
Class and phylum level relationship of Brachiopoda 77
Mode of mesoderm formation 77
Protocoel and prosoma 77
Apical ganglion 77
Mesocoel and lophophore 78
Metacoel and metasoma 78
Literature 79
Class Bryozoa 82
Gymnolaemata 83
Ctenostomata – species with planktotrophic shelled cyphonautes larvae 83
Alcyonidium albidum (ALDER) 83
Hypophorella expansa (EHLERS) 85
Farrella repens (FARRE) 86
Ctenostomata – species with lecithotrophic shelled coronate larvae 87
Flustrellidra hispida (FABRICIUS) 87
Pherusella tubulosa (ELLIS & SOLANDER) 94
Ctenostomata – species with lecithotrophic coronate larvae without shell 95
Alcyonidium gelatinosum (LINNÉ) 95
Triticella flava (DALYELL) 100
Bowerbankia gracilis (LEIDY) 101
Bulbella abscondita (BRAEM) 106
Victorella muelleri (KRAEPELIN) 106
Paludicella articulata (EHRENBERG) 109
Cheilostomata 110
Anasca – species with planktotrophic shelled cyphonautes larvae 110
Electra pilosa (LINNÉ) 110
Membranipora membranacea (LINNÉ) 115
Electra crustulenta (PALLAS) 118
Electra monostachys (BUSK) 120
Conopeum seurati (CANU) 120
Conopeum reticulum (LINNÉ) 120
Anasca – species with lecithotrophic coronate larvae 120
Bugula flabellata (THOMPSON) 120
Bugula neritina (LINNÉ) 123
Tricellaria occidentalis (TRASK) 128
Cheilostomata 129
Ascophora – species with lecithotrophic coronate larvae 129
Watersipora cucullata (BUSK) 129
Watersipora arcuata (BANTA) 130
Stenolaemata 132
Stenostomata – species with polyembryony and lecithotrophic coronate larvae 132
Crisia ramosa (HARMER) 132
Crisia eburnea (LINNÉ) 135
Lichenopora verrucaria (FABRICIUS) 137
Phylactolaemata 141
Plumatella fungosa (PALLAS) 141
Fredericella sultana (BLUMENBACH) 146
Summary of Embryonic Development in Bryozoa 151
Gametes and fertilization 151
Brooding mechanisms in Gymnolaemata 151
Brooding mechanisms in Stenolaemata 152
Brooding mechanisms in Phylactolaemata 152
Embryogenesis in Gymnolaemata 153
Cleavage and gastrulation 153
Larvae of Gymnolaemata 153
Cyphonautes larvae 153
Coronate larvae 154
Metamorphosis of gymnolaemate larvae 155
Embryogenesis in Stenolaemata 155
Embryogenesis in Phylactolaemata 156
Embryonic development in Bryozoa and evolutionary interpretation 156
Hypothetical gymnolaemate larva 157
Coelom cavities in bryozoan larvae 157
Class level relationships of Bryozoa 158
Embryonic and larval features 158
Biradial symmetry in cleavage 158
Endoderm and digestive tract 158
Mesoderm and coelom 158
Metasomal or adhesive sac 159
Pyriform organ 159
Larval corona 159
Ciliated ridge of cyphonautes 160
Adult features 160
Lophophore 160
Coelom cavities 160
Phylum level relationships of Bryozoa 161
Literature 162
Glossary 167