New Horizons in Meiobenthos Research: Profiles, Patterns and Potentials

Description

Since research on meiobenthos was last compiled in a textbook (2008/2009), the number of theoretical and applied studies has been growing rapidly. Supported by new methods and digital evaluation, meiobenthology has developed into a wide field, with more and more researchers studying cross-disciplinary aspects. New perspectives were summarized in a booklet (2019) to draw attention to promising research directions. The present book, written by leading experts, is a compilation of new thinking, data, methods and approaches in many relevant fields of recent meiobenthos research. The topics addressed range from bacteria and biofilms to globally changing processes, from polar regions to the deep-sea and from freshwater ecosystems to the ocean. So, this book is not simply another meiobenthos textbook - it is an attempt to identify new horizons in meiobenthos research, driven by the vision of advancing knowledge and understanding of benthic ecosystems. Acknowledgements Preface Contents 1 Evolution of Bilateria from a Meiofauna Perspective—Miniaturization in the Focus 1.1 Introduction 1.2 Where to Find Meiofauna on the Metazoan Tree of Life? 1.3 Do Common Structural and Functional Traits Exist in Meiofauna? 1.4 Pathways Towards a Secondarily Miniaturized Body 1.4.1 Paedomorphosis 1.4.2 Genetic Mechanisms Underlying Paedomorphosis 1.5 What Can the Fossils Tell Us? 1.5.1 Taphonomy and Windows to Preservation of Meiofauna 1.6 Taphonomic Biases May Explain Distribution Patterns of Fossil Meiofauna 1.6.1 Fossil Evidence for Macroscopic Ancestries to Meiofauna 1.7 Meiofauna Evolution—How to Trace Back Animal Miniatures References 2 Meiofauna Shaping Biogeochemical Processes 2.1 Sediment Biogeochemistry—Of Basic Relevance to Meiobenthos 2.2 The Concept of Meiofauna bioturbation—The “Benthic Fusion” 2.3 Meiofauna and Dominant Chemical Cycling Processes 2.3.1 Carbon Cycle 2.3.2 Sulfur Cycle 2.3.3 Nitrogen Cycle 2.4 Knowledge Gaps and New Research Horizons 2.5 Conclusions References 3 Meiofauna and Biofilms—The Slimy Universe 3.1 Introduction—The Slimy Universe 3.2 What Are the Benefits of Living in the Slimy Universe? 3.2.1 Main Features of the Slimy Universe 3.2.2 The Biofilm Food Web 3.2.3 The Biofilm as a Habitat—A Safe Haven in Stressful and Extreme Environments? 3.3 How Do Meiofauna Contribute to Biofilm Functions? 3.3.1 Biofilm–Meiofauna Systems: A Trophic Powerhouse? 3.3.2 On the Roles of Poking Holes 3.3.3 On the Roles of Mucus 3.4 Applied Research on Biofilm–Meiofauna 3.4.1 Improving Water Purification Processes 3.4.2 Biogenic Stabilization 3.5 Frontiers and Future Horizons References 4 Meiofauna Meets Microbes— Chemosynthetic Symbioses 4.1 Introducing a Special Relation 4.1.1 Why Study Chemosynthetic Symbioses in Meiofauna? 4.2 Ecological Settings 4.3 Introduction to the Organisms Included in this Chapter 4.4 Symbiont Transmission and Physical Integration in Chemosymbiotic Meiofauna 4.4.1 Host-Symbiont Interfaces and Transmission in the Different Taxa 4.5 Structure and Function of Host—Symbiont Interfaces 4.5.1 Symbiosis as a One-Way Street? 4.6 Symbiotic Associations Are a Window into Environmental Bacterial Cell Biology 4.7 Should I Stay or Should I Go? How Chemosynthetic Bacteria Are Chosen by Their Meiofauna Hosts 4.7.1 Immune Receptors 4.7.2 Toll-Like Receptors (TLRs) 4.7.3 G Protein-Coupled Receptors (GPCRs) 4.7.4 Peptidoglycan Receptors (PGRPs) 4.7.5 C-Type Lectin Domain-Containing Proteins (CTLD-Containing Proteins) 4.7.6 Effector Molecules 4.7.7 Environmental Regulation of Host Immunity 4.7.8 Conclusions 4.8 New Insights from the Physiology of Chemosynthetic Symbionts in Meiofauna 4.8.1 Carbon and Energy Sources 4.8.2 Autotrophs, Mixotrophs or Heterotrophs? 4.8.3 Anaplerosis as a New Force to Reckon with in Chemosymbiosis 4.8.4 A Call for Precise and Detailed Physiological Data 4.8.5 Nitrogen Sources 4.8.6 Biomass Transfer and Storage 4.8.7 The Role of the Hosts 4.8.8 Ca. Thiosymbion—The Archetypical Chemosynthetic Symbiont in Meiofaunal Hosts 4.9 Intricate Symbiotic Relationships—Present Frontiers, Emerging Challenges, and Future Research References 5 Marine Meiofauna Diversity and Biogeography—Paradigms and Challenges 5.1 Why Study the Biodiversity and Biogeography of Meiofauna? 5.2 Studying an Invisible World: Sampling and Measuring Meiofauna Biodiversity 5.3 Meiofauna Biodiversity Patterns Across Benthic Habitats 5.4 Environment-Related Drivers of Meiofauna Diversity Patterns 5.5 The Function of Meiofauna Biodiversity 5.6 Looking into the Past to Understand the Future: Fossil Records 5.7 Biogeography of Meiofauna: Hypotheses and Evidence 5.8 The Future of Meiofauna Biogeography and Biodiversity Research: Gaps in Our Knowledge and Research Frontiers References 6 Freshwater Meiofauna—A Biota with Different Rules? 6.1 Introduction 6.2 Research on Meiofauna Species—a New ‘Frontier in Biodiversity’? 6.3 Do Freshwater Meiofauna Hold the Key for Understanding Food Web Topology and Benthic Energy Fluxes? 6.4 Inclusion of Meiobenthos, a Pathway Towards New Metabolic Perspectives of Freshwater Ecology? 6.5 Conclusions References 7 Hidden Players—Meiofauna Mediate Ecosystem Effects of Anthropogenic Disturbances in the Ocean 7.1 Disturbance: A Multifaceted Phenomenon 7.1.1 Under Pressure: Anthropogenic Disturbances in Marine Ecosystems 7.1.2 The Small Majority: Adding Meiofauna to the Bigger Picture 7.2 Fishing for Answers: Response of Meiofauna to Bottom-fishing 7.3 Cohabiting with Harmful Substances: Response of Meiofauna to Pollution 7.3.1 Nutrients and Organic Enrichment 7.3.2 Persistent Chemical Pollutants 7.3.3 Petroleum Hydrocarbons 7.3.4 Resilience to Pollution 7.4 Invaders Among Locals: Response of Meiofauna to the Introduction of Invasive Species 7.5 Living in a Hot, Sour, Breathless, and Disturbed Ocean: Response of Meiofauna to Climate Change 7.6 Scale Matters: Observing the Response of Meiofauna to Anthropogenic Disturbances 7.7 Invisible Allies: New Horizons for Future Meiofauna Research 7.8 Concluding Remarks References 8 Deep-Sea Meiofauna—A World on Its Own or Deeply Connected? 8.1 Introduction 8.2 Trophic Interactions of Deep-Sea Meiofauna: “You Are What You Eat” But What Do Deep-Sea Meiofauna Eat? 8.3 Meiofauna Biodiversity and Ecosystem Function in the Deep Sea 8.4 Distribution and Diversity of Deep-Sea Meiofauna: Local to Global Scale Patterns 8.5 Connectivity, Dispersal, and Origins of Deep-Sea Meiofauna 8.6 Conclusions, Thoughts, and Future Perspectives References 9 Polar Meiofauna—Antipoles or Parallels? 9.1 An Old Continent and a Young Ocean—How Different or Similar Are the Poles? 9.2 Brief Historical Perspective on Polar Meiobenthic Research 9.3 Meiofauna Along Polar Seascapes—From Coasts to Shelf and the Deep Sea, Including Sympagic Ecology 9.3.1 Polar Coastal Areas and Fjords 9.3.2 Polar Continental Shelves and Ice Shelves 9.3.3 Sea Ice and Sympagic Meiofauna 9.3.4 Polar Deep Seas 9.4 Polar Meiofauna and Climate Change—Observations, Conclusions, Prognoses 9.5 Gaps, Directions, and Methods in Polar Meiofauna Research 9.5.1 Future Field Work 9.5.2 Future Experimental Work 9.5.3 Tracking Ecosystem Change in Polar Regions 9.5.4 Adaptations to ‘Extreme’ Polar Environments References 10 Cave Meiofauna—Models for Ecology and Evolution 10.1 Introduction 10.2 An Overview on Cave Meiofauna 10.2.1 Regional Aspects 10.2.2 Taxonomic Composition of Cave Meiofauna: Which Animals Are Found in Caves? 10.2.3 Distribution Patterns of Cave Meiofauna: Different from Other Subterranean Organisms? 10.2.4 What Do We Know About the Phylogenetic Position of Cave Meiofaunal Species? 10.2.5 Evolutionary Origin of Cave Meiofauna: What Do We Know About the Processes Leading to the Origin of Cave Meiofauna? 10.3 An Overview of Cave Meiofaunal Communities 10.4 Emerging from the Dark: New Horizons for the Study of Cave Meiofauna References 11 Meiofauna—Adapted to Life at the Limits 11.1 Extreme Environments and Meiofauna 11.2 ‘Toughest Animals on Earth’ (Erdmann and Kaczmarek 2017) 11.3 Why Are Nematodes so Successful Under Extreme Conditions? 11.4 Adaptive Responses of Nematodes to Extreme Environments 11.4.1 Prevalent Stressors for Nematodes 11.4.2 Interaction Between Stress Factors 11.4.3 A Better Survival with Partners? Nematodes and Their Microbiomes 11.5 Meiofauna Surviving at the Limits 11.5.1 Tardigrada 11.5.2 Rotifera 11.5.3 Foraminifera 11.5.4 Loricifera 11.6 Advantages of Extremobionts and Why to Study Them? New Horizons and Some Conclusions References Concluding Remarks: New Horizons in Meiobenthos Research—Profiles, Patterns and Potentials References Index