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.
Preface 9
Acknowledgement 10
Introduction 11
Characteristics of comparative embryology 11
Biological systematics 12
Eggs and embryos 12
Cleavage 12
Blastula 12
Gastrulation, second germ layer formation 12
Mesoderm, third germ layer formation 13
Organ differentiation 13
Larvae 13
Molecular biology and development 14
Literature 15
Diploblastic Organisms – Animals with two germ layers 16
Phylum Porifera 16
Symplasma* – Class Hexactinellida 16
Cellularia 17
Calcarea 17
Calcaronea 17
Leucosolenia botryoides (ELLIS & SOLANDER) 17
Sycon raphanus (O. SCHMIDT) 20
Grantia compressa (FABRICIUS) 24
Calcinea 26
Ascandra minchini (BOROJEVIC) 26
Clathrina falcata (HAECKEL) 28
Clathrina coriacea (MONTAGU) 28
Demospongiae 30
Homoscleromorpha 30
Oscarella lobularis (O. SCHMIDT) 30
Tetractinomorpha 30
Tethya aurantium (PALLAS) 30
Polymastia robusta (BOWERBANK) 33
Raspailia pumila (BOWERBANK) 34
Ceractinomorpha 35
Myxilla rosea (LIEBERKÜHN) 35
Halisarca dujardini (JOHNSTON) 36
Ephydatia fluviatilis (LINNÉ) 37
Summary of the Ontogenesis in Porifera 40
Cleavage, morula, coeloblastula, amphiblastula 40
Reorganization process of germ layers, parenchymulae, gastrulation, metamorphosis 40
Polarity of the sponge egg and rudiment of germ layers 41
Comparison of ontogenies in Porifera 42
Embryonic development in Porifera and evolutionary interpretation 43
Phylogenetic Transition between Protozoans and Metazoans 44
Comparative embryology 44
Comparative morphology 44
Morphogens 45
Biochemistry of the extracellular matrix 45
Literature 46
Phylum Cnidaria 49
Class Anthozoa 49
Hexacorallia 50
Ceriantharia 50
Cerianthus lloydii (GOSSE) 50
Pachycerianthus multiplicatus (CALGREN) 50
Actinaria 52
Metridium senile var. dianthus (ELLIS) 52
Aiptasia mutabilis (GOSSE) 55
Anthopleura xanthogrammica (BRANDT) 55
Tealia crassicornis (MÜLLER) 56
Madreporaria 56
Favia fragum (ESPER) 56
Platygyra sinensis (EHRENBERG) 57
Zoantharia 58
Protopalythoa spec. 58
Octocorallia 60
Alcyonaria 60
Alcyonium digitatum (LINNÉ) 60
Sympodium coralloides (MILNE EDWARDS) 62
Pennatularia 62
Ptilosarcus guerneyi (GRAY) 62
Helioporida 64
Heliopora coerula (PALLAS) 64
Summary of Ontogenesis in Anthozoa 65
Cleavage and gastrulation 65
Anthozoan larvae 65
Embryonic development in Anthozoa and evolutionary interpretation 66
Comparative embryology 66
Nucleotide sequence data 67
Structure of the mitochondrial genome 67
Literature 67
Class Scyphozoa 69
Coronata 71
Linuche unguiculata (SCHWARTZ) 71
Semaeostomea 71
Chrysaora hysoscella (LINNÈ) 71
Cyanea capillata (LINNÈ) 72
Aurelia aurita (LAMARCK) 73
Rhizostomea 75
Cassiopea andromeda (FORSKAL) 75
Cotylorhiza tuberculata (MACRI) 76
Mastigias papua (LINNÉ) 78
Stauromedusida 78
Haliclystus octoradiatus (LAMARCK) 80
Class Cubozoa 80
Tripedalia cystophora (CONANT) 80
Carybdea rastoni (HAACKE) 82
Summary of Ontogenesis in Scyphozoa and Cubozoa 82
Cleavage and gastrulation 82
Scyphozoan and cubozoan larvae 82
Embryonic development in Scyphozoa and Cubozoa and evolutionary interpretation 82
Comparative embryology 82
Comparative morphology 83
Nucleotide sequence data 83
Literature 83
Class Hydrozoa 84
Hydroidea 84
Thecata – Leptomedusae 84
Aequorea aequorea (PÉRON & LESUEUR) 84
Eucheilota maculata (HARTLAUB) 86
Clytia gregaria (AGASSIZ) 86
Phialidium hemisphaericum (LINNÈ) 87
Obelia longissima (PALLAS) and Obelia geniculata (LINNÉ) 88
Athecata – Anthomedusae 90
Clava multicornis (O. F. MÜLLER) 90
Cordylophora caspia (PALLAS) 93
Podocoryne carnea (SARS) 93
Hydractinia echinata (FLEMING) 96
Eudendrium armatum (TICHOMIROV) 96
Coryne muscoides (LINNÉ) 98
Sarsia eximia (ALLMAN) 100
Tubularia mesembryanthemum (ALLMAN) 100
Tubularia crocea (AGASSIZ) 100
Hydrina 103
Hydra grisea (LINNÉ) 103
Hydra carnea (AGASSIZ) 103
Hydra vulgaris (PALLAS) 104
Lymnohydrina 104
Gonionemus vertens (AGASSIZ) 104
Trachylida 104
Geryonia fungiformis (METSCHNIKOFF) 104
Summary of Ontogenesis in Hydrozoa 106
Cleavage and gastrulation 106
Endoderm 107
Hydrozoan larvae 107
Composition of the extracellular matrix (mesogloea) 107
Embryonic development in Hydrozoa and evolutionary interpretation 107
Literature 108
Class level relationships in the phylum Cnidaria 110
Comparative embryology 110
Comparative morphology 110
Structure of the mitochondrial genome 111
Phylogeny of Cnidaria 111
Literature 111
Phylum Ctenophora 113
Tentaculifera 114
Cydippida 114
Pleurobrachia pileus (O. F. MÜLLER) 114
Callianira bialata (DELLE CHIAJE) 114
Lobata 115
Mnemiopsis leidyi (AGASSIZ) 115
Ocyropsis maculata (RANG) and Ocyropsis crystallina (RANG) 119
Atentaculata 120
Beroida 120
Beroe ovata (CHAMISSO and EYSENHARDT) 120
Summary of the Ontogenesis in Ctenophora 123
Cleavage and gastrulation 123
Embryonic development in Ctenophora and evolutionary interpretation 123
Mesogloea in Ctenophora 123
Comparative embryology 123
Comparative morphology 124
Nucleotide sequence data 124
Literature 124
Phylum Placozoa 126
Literature 126
Ancestral mode of ontogeny in diploblastic animals 127
Cleavage pattern 127
Gastrulation 127
Second germ layer hypothesis 127
The bilaterogastraea-theory 130
Blastopore formation 130
Phylum-level relationships, molecular biology and traditional homology 131
Protostomia versus Deuterostomia 131
Comparative embryology 131
Molecular biology 131
Developmental genetics and “homology” 132
Literature 132
Glossary 135