Preface

In the present volume, we exhibit a broad panorama of the current status of cnidarian research. On the timescale, the cnidarians are traced from the earliest geological records of their place at the very cradle of the evolution of multicellular organisms in the Earth’s primordial oceans, to their response to present climate change effects in the warming and acidifying oceans. The latter aspects are described on the molecular and physiological responses followed by resulting population level effects. Their evolution is accompanied by their taxonomic diversification and geographic expansion, including their present role among invasive species. Their acquisition of neural networks and development of skeletal elements are described on the background of the evolutionary history of these systems covering both evolutionary and ontogenetic analyses. The uniquely widespread and intimate mutualistic symbiotic associations with algae is described in taxa, such as jellyfishes and corals, revealing the roots of the dependence of so many cnidarian species on photosynthesis. That allows their symbiotic algae – the zooxanthel- lae – to provide most of the metabolic energy needs of the animal algae holobiont. Due to the dominant role of corals in the biogeochemical carbon and calcium cycles, the various aspects of cnidarian calcification are discussed in terms of accepted theories while exposing their difficulties. The relation of the Cnidaria with mankind is approached on several levels, in accordance with the editors’ philosophy of bridging the artificial schism between science, arts and humani- ties. On the direct level, the various encounters with humans result in a broad spectrum of medical emergencies of varying seriousness are reviewed. On a more detached level, humans from the very emergence of our species were fascinated by corals, and various coralline orna- mental objects are found in burial sites in coastal regions in all continents. Chapters are dedi- cated to the history of coral harvesting down to current sustainable culture practices. To the role of “Hydra” and “Medusa” in mythology, art and culture is devoted in the final section of the volume. That section closes the unique, topical, multi-level, interdisciplinary coverage of the wide- spread, predominantly marine taxon, the Cnidaria. The present volume takes the reader through the earliest evolution of the taxon and the ramification of its diversity. It proceeds to the group’s molecular and genomic make-up, through its ecology and physiology, all the way to its use in jewellery and invasion of human imagination in art and myth. Bologna, Italy Stefano Goffredo Ramat-Gan, Israel Zvy Dubinsky