Thorp and Covich's Freshwater Invertebrates: Volume 4: Keys to Palaearctic Fauna

By James H. Thorp

Thorp and Covich's Freshwater Invertebrates: Keys to Palaearctic Fauna, Fourth Edition, is part of a multivolume series covering inland water invertebrates of the world that began with Vol. I: Ecology and General Biology (2015), then Vol. II (2016) Keys to Nearctic Fauna, and finally in Vol. III (2018) Keys to Neotropical Hexapoda (insects and springtails). It now continues with identification keys for Palearctic invertebrates in Vol. IV. Two other volumes currently in development focus on general invertebrates of the Neotropical/Antarctic, and Australasian Bioregions. Other volumes in the early planning stages include Afrotropical and Oriental/Oceanic Bioregions. All volumes are designed for multiple uses and levels of expertise by professionals in universities, government agencies and private companies, as well as by graduate and undergraduate students.

• Provides identification keys for inland water (fresh to saline) invertebrates of the Palearctic Zoogeographic Region, from Iceland to Russia, and from the northern Pole region to Saharan Africa in the west, through the Middle East, and to the central China and Japan in the east
• Presents identification keys for aquatic invertebrates to the genus or species level for many groups and to family for Hexapoda, with the keys progressing from higher to lower taxonomic levels
• Includes a general introduction and sections on limitations, terminology and morphology, material preparation and preservation and references

• Language: English
• Publisher: Academic Press
• Release date: Mar 31, 2019
• ISBN: 9780123850256

Book preview

Keys to Palaearctic Fauna

Thorp and Covich’s Freshwater Invertebrates – Volume IV

Fourth Edition

Editors

D. Christopher Rogers

Kansas Biological Survey and The Biodiversity Institute, University of Kansas, Lawrence, KS, USA

James H. Thorp

Kansas Biological Survey and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA

Table of Contents

Cover image

Title page

Thorp and Covich's Freshwater Invertebrates

Copyright

Dedications From the Editors

Contributors to Volume IV

About the Editors

Preface to the Fourth Edition

Preface to Volume IV

Acknowledgments for Volume IV

Chapter 1. Introduction

Introduction to This Series, Volume, and Chapter

Nature and Fauna of the Palaearctic Bioregion

Components of Taxonomic Chapters

How to Use This Volume

Keys to Major Taxa of Inland Water Invertebrates of the Palaearctic

Part I

Chapter 2. Protozoa

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Acknowledgments

Keys to Protozoa

Chapter 3. Phylum Porifera

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Acknowledgments

Keys to Spongillida

Chapter 4. Phylum Cnidaria

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Keys to Cnidaria

Chapter 5. Phylum Platyhelminthes

Introduction

Limitations

Terminology and Morphology

Abbreviations Used in Figures

Material Preparation and Preservation

Keys to Platyhelminthes

Chapter 6. Phylum Nemertea

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Keys to Nemertea

Chapter 7. Phylum Gastrotricha

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Keys to Gastrotricha

Chapter 8. Phylum Rotifera

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Key to Rotifers

Chapter 9. Phylum Nematoda

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Keys to Nematoda

Chapter 10. Phylum Nematomorpha

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Keys to Gordiida

Chapter 11. Phylum Mollusca

Introduction to the Phylum

Class Gastropoda

Class Bivalvia

Chapter 13. Phylum Ectoprocta

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Keys to Ectoprocta (Bryozoa)

Chapter 14. Phylum Entoprocta

Introduction

Terminology and Morphology

Material Preparation and Preservation

Chapter 15. Phylum Tardigrada

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Keys to Tardigrada

Part II

Chapter 16. Phylum Arthropoda: Introduction and Arachnida

Introduction to Arthropoda

Arachnida: Acari: Trombidiformes: Halacaridae

Chapter 16.1. Arthropoda: Introduction to Crustacea and Hexapoda

Introduction to the Subphylum Crustacea

Crustacea: Hexapoda

Chapter 16.2. Arthropoda: Class Branchiopoda

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Keys to Branchiopoda

Chapter 16.3. Arthropoda: Ostracoda

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Acknowledgments

Keys to Ostracoda

Chapter 16.4. Arthropoda: Copepoda

Introduction

Limitations

Terminology and Morphology

Material Preparation and Preservation

Keys to Copepoda

Chapter 16.5. Arthropoda: Thecostraca

Introduction to Thecostraca

Thecostraca: Subclass Sessilia

Chapter 16.6. Phylum Arthropoda: Malacostraca

Introduction to Malacostraca

Malacostraca: Cumacea

Malacostraca: Bathynellacea

Malacostraca: Amphipoda

Malacostraca: Tanaidacea

Malacostraca: Isopoda

Malacostraca: Thermosbanacea

Malacostraca: Decapoda

Malacostraca: Mysida and Stygiomysida

Taxonomic Index

Thorp and Covich's Freshwater Invertebrates

A Global Series of Books on the Identification, Ecology, and General Biology of Inland Water Invertebrates by Experts from Around the World

Fourth Edition

Series Editor: James H. Thorp

Volume I: Ecology and General Biology

Edited by James H. Thorp and D. Christopher Rogers

Published 2015

Volume II: Keys to Nearctic Fauna

Edited by James H. Thorp and D. Christopher Rogers

Published 2016

Volume III: Keys to Neotropical Hexapoda

Edited by Neusa Hamada, James H. Thorp, and D. Christopher Rogers

Published 2018

Volume IV: Keys to Palaearctic Fauna

Edited by D. Christopher Rogers and James H. Thorp

Published 2019

Volumes in Preparation for Future Publication

Keys to Neotropical and Antarctic Fauna (2019)

Keys to Australasian Fauna (2020)

Keys to Afrotropical Fauna (2023)

Planned Future Volumes

Keys to Oriental and Oceana Hexapoda

Keys to Oriental and Oceana Fauna

Keys to Palaearctic Hexapoda

Keys to Nearctic Hexapoda

Related Publications

Field Guide to Freshwater Invertebrates of North America

James H. Thorp and D. Christopher Rogers

First Edition (2011)

Copyright

Academic Press is an imprint of Elsevier

125 London Wall, London EC2Y 5AS, United Kingdom

525 B Street, Suite 1650, San Diego, CA 92101, United States

50 Hampshire Street, 5th Floor, Cambridge, MA 02139, United States

The Boulevard, Langford Lane, Kidlington, Oxford OX5 1GB, United Kingdom

Copyright © 2019 Elsevier Inc. All rights reserved.

No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Details on how to seek permission, further information about the Publisher’s permissions policies and our arrangements with organizations such as the Copyright Clearance Center and the Copyright Licensing Agency, can be found at our website: www.elsevier.com/permissions.

This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein).

Notices

Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.

Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.

To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein.

Library of Congress Cataloging-in-Publication Data

A catalog record for this book is available from the Library of Congress

British Library Cataloguing-in-Publication Data

A catalogue record for this book is available from the British Library

ISBN: 978-0-12-385024-9

For information on all Academic Press publications visit our website at https://www.elsevier.com/books-and-journals

Publisher: Candice Janco

Acquisitions Editor: Louisa Munro

Editorial Project Manager: Emily Thomson

Production Project Manager: Paul Prasad Chandramohan

Cover Designer: Greg Harris

Cover Photographs courtesy of (from top): Vadim Takhteev, Rafael Araujo, and Gintautas Steiblys

Typeset by TNQ Technologies

Dedications From the Editors

To our authors who made this book possible.

D. Christopher Rogers

To my loving wife of nearly half a century who has tolerated my occasional frustrations with my profession while showing great interest in my studies, and to the students working in my lab over the decades who have never failed to inspire and challenge me while reinforcing in my mind the true value of being a professor.

James H. Thorp

Contributors to Volume IV

Eyualem Abebe email address: [e-mail] [Chapter 9],     Department of Natural Sciences, Pharmacy and Health Professions, Elizabeth State University, Elizabeth City, NC, United States

Boris Anokhin email address: [e-mail] [Chapter 4],     Zoological Institute RAS, Universitetskaya nab. 1, St. Petersburg, Russia

Rafael Araujo email address: [e-mail] [Chapter 11 (Bivalvia)],     Museo Nacional de Ciencias Naturales, Madrid, Spain

Bonnie A. Bain email address: [e-mail] [Chapter 12 (Hirudinida)],     Department of Biological Sciences, Southern Utah University, Cedar City, UT, United States

Maria Balsamo email address: [e-mail] [Chapter 7],     Department of Biomolecular Sciences (DISB), University of Urbino, Carlo Bo, Urbino, Italy

Ilse Bartsch email address: [e-mail] [Chapter 16],     Forschungsinstitut Senckenberg, Hamburg, Germany

Eugeniya I. Bekker email address: [e-mail] [Chapter 16.2],     A. N. Severtsov Institute of Ecology and Evolution, Moscow, Russia

Aleksander Bielecki email address: [e-mail] [Chapter 12 (Hirudinida)],     Department of Zoology, Faculty of Biology and Biotechnology, University of Warmia and Mazury in Olsztyn, Olsztyn, Poland

Dirk Brandis email address: [e-mail] [Chapter 16.6 (Decapoda)],     Zoological Museum, University of Kiel, Kiel, Germany

Mikhail E. Daneliya email address: [e-mail] [Chapter 16.6 (Mysida and Stygomysida)],     Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland

Wilfrida Decraemer email address: [e-mail] [Chapter 9]

Department of Biology, Ghent University, Ghent, Belgium

Department of Taxonomy & Phylogeny, Royal Belgian Institute of Natural Sciences, Brussels, Belgium

R. Edward DeWalt email address: [e-mail] [Chapter 16.1],     University of Illinois, Prairie Research Institute, Illinois Natural History Survey, Champaign, IL, United States

Jean-Loup d’Hondt email address: [e-mail] [Chapter 7],     Département Milieux et Peuplements Aquatiques, Muséum National d'Histoire Naturelle, Paris, France

Ursula Eisendle-Flöckner email address: [e-mail] [Chapter 9],     Department of Cell Biology and Physiology, University of Salzburg, Salzburg, Austria

Genoveva F. Esteban email address: [e-mail] [Chapter 2],     Bournemouth University, Faculty of Science and Technology, Department of Life and Environmental Sciences, Dorset, United Kingdom

Stuart R. Gelder email address: [e-mail] [Chapter 12 (Branchiobdellida)],     Department of Science and Math, University of Maine at Presque Isle, Presque Isle, ME, United States

João Gil email address: [e-mail] [Chapter 12 (Aphanoneura; Polychaeta)],     CCMAR, Universidade do Algarve, Faro, Portugal

Sergei M. Glagolev email address: [e-mail] [Chapter 16.2],     Moscow South-West High School, Moscow, Russia

Christopher J. Glasby email address: [e-mail] [Chapter 12 (Aphanoneura; Polychaeta)],     Museum & Art Gallery Northern Territory, Darwin, NT, Australia

Fredric R. Govedich email address: [e-mail] [Chapter 12 (Hirudinida)],     Department of Biological Sciences, Southern Utah University, Cedar City, UT, United States

Paolo Grilli email address: [e-mail] [Chapter 7],     Department of Biomolecular Sciences (DISB), University of Urbino Carlo Bo, Urbino, Italy

Roberto Guidetti email address: [e-mail] [Chapter 15],     Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy

Tom Hansknecht email address: [e-mail] [Chapter 16.6 (Tanaidacea)],     Barry Vittor & Associates, Inc., Mobile, AL, United States

David J. Horne email address: [e-mail] [Chapter 16.3],     School of Geography, Queen Mary, University of London, London, United Kingdom

Thomas Jankowski email address: [e-mail] [Chapter 4],     Teningen, Germany

Sebastian Klaus email address: [e-mail] [Chapter 16.6 (Decapoda)],     Department of Ecology & Evolution, Goethe-University – Biologicum, Frankfurt am Main, Germany

Nikolai M. Korovchinsky email address: [e-mail] [Chapter 16.2],     A. N. Severtsov Institute of Ecology and Evolution, Moscow, Russia

Alexey A. Kotov email address: [e-mail] [Chapter 16.2],     A. N. Severtsov Institute of Ecology and Evolution, Moscow, Russia

Dong Ju Lee email address: [e-mail] [Chapter 16.4],     Department of Life Science, Hanyang University, Seoul, Republic of Korea

Wonchoel Lee email address: [e-mail] [Chapter 16.4],     Department of Life Science, Hanyang University, Seoul, Republic of Korea

Julian J. Lewis email address: [e-mail] [Chapter 16.6 (Isopoda)],     Lewis & Associates LLC, Borden, IN, United States

Lawrence L. Lovell email address: [e-mail] [Chapter 12 (Introduction to the Phylum)],     Research and Collections, Natural History Museum of Los Angeles County, Los Angeles, CA, United States

Renata Manconi email address: [e-mail] [Chapter 3],     Dipartimento di Medicina Veterinaria, Università di Sassari, Sassari, Italy

Koen Martens email address: [e-mail] [Chapter 16.3],     Royal Belgian Institute of Natural Sciences, Freshwater Biology, Brussels, Belgium

Daniel Martin email address: [e-mail] [Chapter 12 (Aphanoneura; Polychaeta)],     CEAB-CSIC, Blanes, Catalunya, Spain

Patrick Martin email address: [e-mail] [Chapter 12 (Oligochaeta)],     Royal Belgian Institute of Natural Sciences, Operational Directorate Taxonomy & Phylogeny, Brussels, Belgium

Claude Meisch email address: [e-mail] [Chapter 16.3],     Musée national d'histoire naturelle, Luxembourg

Hiroshi Morino email address: [e-mail] [Chapter 16.6 (Amphipoda)],     Department of Zoology, National Museum of Nature and Science, Tsukuba, Ibaraki, Japan

William E. Moser email address: [e-mail] [Chapter 12 (Hirudinida)],     Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Suitland, MD, United States

Takafumi Nakano email address: [e-mail] [Chapter 12 (Hirudinida)]

Department of Science Education, Graduate School of Education, Hiroshima University, Higashihiroshima, Japan

Department of Zoology, Graduate School of Science, Kyoto University, Kyoto, Japan

Tohru Naruse email address: [e-mail] [Chapter 16.6 (Decapoda)],     Tropical Biosphere Research Center, University of the Ryukyus, Taketomi, Japan

Diane R. Nelson email address: [e-mail] [Chapter 15],     Department of Biological Sciences, East Tennessee State University, Johnson City, TN, United States

Ngan Kee Ng email address: [e-mail] [Chapter 16.6 (Decapoda)],     Department of Biological Sciences, National University of Singapore, Republic of Singapore

Carolina Noreña email address: [e-mail] [Chapter 5],     Departamento Biodiversidad y Biología Evolutiva, Museo Nacional de Ciencias Naturales (CSIC), Madrid, España

Sameer Kumar Pati email address: [e-mail] [Chapter 16.6 (Decapoda)],     Zoological Survey of India, Western Regional Centre, Pune, India

Victor V. Petryashov email address: [e-mail] [Chapter 16.6. (Mysida and Stygiomysida)],     Zoological Institute of the Russian Academy of Sciences, Saint Petersburg, Russia

Andrey Porfiriev email address: [e-mail] [Chapter 5],     Kazan State University, Kazan, Russia

Roberto Pronzato email address: [e-mail] [Chapter 3],     Dipartimento di Scienze della Terra, dell'Ambiente e della Vita (DISTAV), Università di Genova, Genova, Italy

Lorena Rebecchi email address: [e-mail] [Chapter 15],     Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy

Vincent H. Resh email address: [e-mail] [Chapter 16.1 (Hexapoda)],     Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, United States

D. Christopher Rogers email address: [e-mail] [Chapters 1, 11, 16, 16.1, 16.2, 16.5, 16.6],     Kansas Biological Survey and The Biodiversity Institute, University of Kansas, Lawrence, KS, United States

S.S.S. Sarma email address: [e-mail] [Chapter 8],     Universidad Naćional Autónoma de México Campus Iztacala, México City, México

Andreas Schmidt-Rhaesa email address: [e-mail] [Chapter 10],     Zoological Museum, University Hamburg, Hamburg, Germany

Hendrik Segers email address: [e-mail] [Chapter 8],     Royal Belgian Institute of Natural Sciences, Brussels, Belgium

Artem Y. Sinev email address: [e-mail] [Chapter 16.2],     Department of Invertebrate Zoology, Biological Faculty, M.V. Lomonosov Moscow State University, Leninskie Gory, Moscow, Russia

Boris Sket email address: [e-mail] [Chapter 16.6 (Amphipoda)],     Biology department, Biotechnical Faculty, Univerza v Ljubljani, Slovenia

Nikolai N. Smirnov email address: [e-mail] [Chapter 16.2],     A. N. Severtsov Institute of Ecology and Evolution, Moscow, Russia

T.W. Snell email address: [e-mail] [Chapter 8],     School of Biology, Georgia Institute of Technology, Atlanta, GA, United States

Malin Strand email address: [e-mail] [Chapter 6],     The Swedish Species Information Centre, Swedish University of Agricultural Sciences, Uppsala, Sweden

Per Sundberg email address: [e-mail] [Chapter 6],     Department of Marine Sciences, University of Gothenburg, Gothenburg, Sweden

Vadim Takhteev email address: [e-mail] [Chapter 16.6 (Amphipoda)],     Department of Invertebrate Zoology & Hydrobiology, Irkutsk State University, Russia

James H. Thorp email address: [e-mail] [Chapters 1, 12],     Kansas Biological Survey and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, United States

Tarmo Timm email address: [e-mail] [Chapter 12 (Oligochaeta)],     Institute of Agricultural and Environmental Sciences, Centre for Limnology, Estonian University of Life Sciences, Tartu, Estonia

Oleg Timoshkin email address: [e-mail] [Chapter 5],     Limnological Institute, Ulan-Batorskaya, Irkutsk, Russia

Serge Utevsky email address: [e-mail] [Chapter 12 (Hirudinida)],     Department of Zoology and Animal Ecology, V.N. Karazin Kharkiv National University, Kharkiv, Ukraine

Risto Väinölä email address: [e-mail] [Chapter 16.6 (Mysida and Stygiomysida)],     Finnish Museum of Natural History, University of Helsinki, Helsinki, Finland

Robert J. Van Syoc email address: [e-mail] [Chapter 16.5 (Sessilia)],     California Academy of Sciences, San Francisco, CA, United States

Maxim V. Vinarski email address: [e-mail] [Chapter 11 (Gastropoda)],     Saint-Petersburg State University, Saint-Petersburg, Russia

Robert L. Wallace email address: [e-mail] [Chapter 8],     Department of Biology, Ripon College, Ripon, WI, United States

E.J. Walsh email address: [e-mail] [Chapter 8],     Department of Biological Science, University of Texas at El Paso, El Paso, TX, United States

Alan Warren email address: [e-mail] [Chapter 2],     Department of Life Sciences, Natural History Museum, London, United Kingdom

Les Watling email address: [e-mail] [Chapter 16.6 (Cumacea)],     Department of Biology, University of Hawaii at Mānoa, Honolulu, HI, United States

Timothy S. Wood email address: [e-mail] [Chapters 13-14],     Department of Biological Sciences, Wright State University, Dayton, OH, United States

Darren C.J. Yeo email address: [e-mail] [Chapter 16.6 (Decapoda)],     Department of Biological Sciences, National University of Singapore, Republic of Singapore

About the Editors

Dr. D. Christopher Rogers is a research zoologist at the University of Kansas with the Kansas Biological Survey and is affiliated with the Biodiversity Institute. He received his Ph.D. degree from the University of New England in Armidale, NSW, Australia. Christopher specializes in freshwater crustaceans (particularly Branchiopoda and Malacostraca) and the invertebrate fauna of seasonally astatic wetlands on a global scale. He has numerous peer-reviewed publications in crustacean taxonomy and invertebrate ecology, as well as published popular and scientific field guides and identification manuals to freshwater invertebrates. Christopher is an Associate Editor for the Journal of Crustacean Biology and a founding member of the Southwest Association of Freshwater Invertebrate Taxonomists. He has been involved in aquatic invertebrate conservation efforts all over the world.

Dr. James H. Thorp has been a Professor in the Department of Ecology and Evolutionary Biology at the University of Kansas (Lawrence, KS, USA) and a Senior Scientist in the Kansas Biological Survey since 2001. Prior to returning to his alma mater, Prof. Thorp was a Distinguished Professor and Dean at Clarkson University, Department Chair and Professor at the University of Louisville, Associate Professor and Director of the Calder Ecology Center of Fordham University, Visiting Associate Professor at Cornell, and Research Ecologist at the University of Georgia's Savannah River Ecology Laboratory. He received his Baccalaureate from the University of Kansas (KU) and both Masters and Ph.D. degrees from North Carolina State. Those degrees focused on zoology, ecology, and marine biology, with an emphasis on the ecology of freshwater and marine invertebrates. Dr. Thorp has been on the editorial board of three freshwater journals and is a former President of the International Society for River Science. He teaches freshwater, marine, and invertebrate courses at KU, and his Masters and Doctoral graduate students work on various aspects of the ecology of communities through macrosystems in rivers, reservoirs, and wetlands. Prof. Thorp's research interests and background are highly diverse and span the gamut from organismal biology to community, ecosystem, and macrosystem ecology. He works on both fundamental and applied research topics using descriptive, experimental, and modeling approaches in the field and lab. While his research emphasizes aquatic invertebrates, he also studies fish ecology, especially as related to food webs. He has published more than one hundred refereed journal articles, books, and chapters, including three single-volume editions of Ecology and Classification of North American Freshwater Invertebrates (edited by J.H. Thorp and A.P. Covich) and three volumes in the current fourth edition of Thorp and Covich's Freshwater Invertebrates.

Preface to the Fourth Edition

Those readers familiar with the first three editions of our invertebrate book (Ecology and Classification of North American Freshwater Invertebrates, edited by J.H. Thorp and A.P. Covich) will note that the fourth edition has expanded from a North American focus to worldwide coverage of inland water invertebrates. We gave our book series on inland water invertebrates the name Thorp and Covich's Freshwater Invertebrates to: (1) associate present with past editions, unite current volumes, and link to future editions; (2) establish a connection between the ecological and general biology coverage in Volume I with the taxonomic keys in the remaining volumes; and (3) give credit to Professor Alan Covich for his work on the first three editions. For the sake of brevity, we refer to the current edition as T&C IV. Whether a fifth edition of T&C will ever appear is certainly problematic, but who knows? At present we are considering producing up to 12 volumes in the fourth edition.

While I am the sole editor of the series at this point, Dr. D. Christopher Rogers has been a major and highly valued partner in developing ideas for the fourth edition and is thus far a coeditor on the first four volumes in print (senior editor on the fourth) as well as on the three volumes in development. He is also likely to play a major role in many of the remaining volumes because of his diverse and global knowledge of freshwater invertebrates, especially in the area of taxonomy. As we made significant progress on the first seven volumes, we began contacting potential coeditors to develop two more volumes for another zoogeographic region, and negotiations with those potential editors are now underway. However, we are still seeking experts in fields of invertebrate taxonomy for various zoogeographic regions to serve as highly dependable coeditors, especially those who both work and live in the zoogeographic regions covered by the various future volumes.

Our concept for T&C IV included producing one book (Vol. I in 2015) with six chapters on general environmental issues applicable to many invertebrates, followed by 35 chapters devoted to individual taxa at various levels (order to phylum, or even multiple phyla in the case of the protozoa). Volume I was designed both as an independent book on ecology and general biology of the various freshwater invertebrate taxa and as a companion volume for users of the keys in the regional taxonomic volumes, thereby reducing the amount of information duplicated in the taxonomic volumes. The perhaps 11 taxonomic volumes we foresee publishing in this series will contain both keys for identifying invertebrates in specific zoogeographic regions and descriptions of detailed anatomical features needed to employ those keys.

While the vast majority of authors in T&C I–III were from the USA or Canada, we attempted in the global volumes of T&C IV to attract authors from many additional countries on six continents. Although we largely succeeded in this goal, we expect the fifth edition of T&C—if it is ever published—to continue increasing the proportion of authors from outside North America as our books become better known internationally.

Our goals for T&C IV are to improve the state of taxonomic and ecological knowledge of inland water invertebrates, to help protect our aquatic biodiversity, and to encourage more students to devote their careers to working with these fascinating organisms. These goals are especially important because the verified and probable losses of species in wetlands, ponds, lakes, creeks, and rivers around the globe exceed those in most terrestrial habitats.

James H. Thorp

Preface to Volume IV

This is the fourth volume of the fourth edition of Thorp and Covich's Freshwater Invertebrates (T&C IV), and the second to focus on a bioregion outside the Nearctic. Information on the ecology and general biology of the groups can be found in Volume I (Ecology and General Biology, edited by Thorp & Rogers, 2015), the companion text for the current and all remaining books in this series. All taxonomic volumes (other than those focused exclusively on Hexapoda) are expected to consist of an introductory chapter, a chapter on protozoa (multiple kingdoms), and multiple chapters on individual phyla from Cnidaria to various groups within Arthropoda. Some of the chapters are very small (e.g., Chapter 14 on Entoprocta), whereas others are quite large. A major change in Volume IV is the division of the single chapter on Arthropoda found in Volume II (which represented more than half the pages of that volume) into a separate section encompassing six chapters.

A typical chapter includes a short introduction, a brief discussion of limits to identification of taxa in that chapter, important information on terminology and morphology that is needed to use the keys, techniques for preparing and preserving material for identification (also covered in Volume I), the taxonomic keys, and a few references. In the large chapters on Mollusca (11), Annelida (12), and Arthropoda (16–22), different individuals have contributed separate sections, and thus there are multiple sections on introduction through keys and references. While this may confuse some readers, it has allowed us to gain contributions from an increased number of experts around the world.

The multilevel keys are formatted to enable users to work easily at the level of their taxonomic expertise and the needs of their project. For that reason, we separated keys by major taxonomic divisions. For example, a student in a college course might work through one or more of the initial crustacean keys to determine the family in which a freshwater shrimp belongs. In contrast, someone working on an environmental monitoring project might need to identify a crayfish or crab to genus or even species, and thus would use the relevant, detailed keys that require more background experience. We also designed most keys, where possible, to proceed from a general to a specific character within a couplet.

We have asked authors to include only taxa that are recognized internationally by publication in reputable scientific journals which follow the International Code of Zoological Nomenclature. Thus, no taxa that have merely been proposed should have been included, even if they have been identified by the world's expert on that group. Common species are not designated in the keys themselves because a common species in one area may not be common in another, and this designation can lead to overly frequent and false identifications. Authors have been encouraged to end the keys at the point where further identification without genetic analysis is not practical or when it is clear that too many of the extant fauna have yet to be described in scientific publications.

Users of these keys need to realize that taxonomy is a growing and vibrant field in which new taxa are being described and previously accepted relationships re-evaluated. For some users, this volume may be sufficient for their needs, but for others a companion text listing known species in a smaller geographic region may also be helpful.

This edition is strongly focused on species found in fresh through saline inland waters, with a nonexclusive emphasis on surface waters, thereby reflecting the bias of existing scientific literature. Again, most estuarine and parasitic species are not covered in this book, but we do discuss species whose life cycle includes a free-living stage (e.g., Nematomorpha) and species that live in hard freshwaters through to brackish waters, even though they may be normally associated with estuarine or marine habitats in some parts of their life cycles (e.g., some shrimp and crabs).

It is our hope that scientists and students from around the world will benefit from this volume, especially those studying organisms in the Palaearctic. Suggestions for improving future volumes are welcomed.

Editors

D. Christopher Rogers

James H. Thorp

Acknowledgments for Volume IV

Many people contributed to this volume in addition to the chapter authors and those acknowledged in individual chapters. We greatly appreciate all our colleagues who have contributed information, figures, or reviews to Volume III and also thank those who provided similar services for the earlier editions, upon which the present book partially relies. We are again grateful to the highly competent people at Academic Press/Elsevier who helped in many aspects of the book's production from the original concept to the final marketing. In particular, we appreciate our association with Elsevier editors including Emily Thomson and Louisa Munro and earlier Laura Kelleher, as well as the entire global production teams for Elsevier.

D. Christopher Rogers

James H. Thorp

Chapter 1

Introduction ¹

James H. Thorp     Kansas Biological Survey and Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, United States

D. Christopher Rogers     Kansas Biological Survey and The Biodiversity Institute, University of Kansas, Lawrence, KS, United States

Abstract

Chapter 1 introduces the reader to our series on inland water invertebrates, with the focus of this volume on invertebrates found from Iceland in the west to western Russia, and the Arctic coastline in the north to northern Africa in the south. This chapter introduces the nature and fauna of the Palaearctic Bioregion, discusses the components of the following taxonomic chapters, describes how to use the taxonomic keys in this volume and provides a key to phyla and individual chapters.

Keywords

Fauna of the Palaearctic; Use of taxonomic keys; Phyla of the Palaearctic

Chapter Outline

Introduction to This Series, Volume, and Chapter

Nature and Fauna of the Palaearctic Bioregion

Components of Taxonomic Chapters

How to Use This Volume

Keys to Major Taxa of Inland Water Invertebrates of the Palaearctic

References

Introduction to This Series, Volume, and Chapter

The first volume of Thorp and Covich's Freshwater Invertebrates (Thorp & Rogers, 2015) provided global coverage of the ecology, general biology, phylogeny, and collection techniques for inland water invertebrates. The focus of all volumes in our series after Volume I has been or will be on taxonomic keys for individual bioregions of the world. The taxonomic keys provide users with means to work at their level of need and expertise. Our authors have tried to limit the specificity of the keys to those taxa where comprehensive knowledge is available for most taxa in a particular group or where identification is only possible for certain life stages. It is our hope that these books demonstrate the limits of our knowledge on the biodiversity for different regions and taxa, and thus will inspire future studies in those areas.

In addition to the first four volumes currently in print (Thorp & Rogers, 2015, 2016; Hamada et al., 2019; and the current volume), two volumes in the series may appear in 2019–2020: (1) Keys to Neotropical and Antarctic Fauna (Damborenea et al., 2019, in prep.); and (2) Keys to Australasian Fauna (Ahyong et al., 2020, in prep). Future volumes will cover Afrotropical Fauna (Day et al.; perhaps in 2022) and Oriental/Oceana fauna (each with one to two volumes) as well as more detailed coverage of Hexapoda in the Nearctic and Palaearctic Bioregions. We consider this series of 10–12 volumes to be a globally expanded, fourth edition of the earlier Ecology and Classification of North American Freshwater Invertebrates (edited by Thorp & Covich in 1991, 2001, and 2010). While some labs may have multiple copies of the Keys to Fauna in their region, we also recommend that they have at least one copy of Volume I to obtain useful background information on each invertebrate group.

The current chapter is organized into an introduction, a description of the taxonomic focus of this particular volume, a section explaining the organization of most taxonomic chapters, and a key to larger taxonomic groups. This chapter's key is designed to help the reader locate the most pertinent chapter (a task probably useful mostly for students and relatively novice taxonomists) and begin identifying organisms in their samples. Readers will note that chapters within and among volumes vary in the specificity of their taxonomic keys. This reflects both the likely percent of the fauna that has been named and how easily taxa can be separated by alpha taxonomic methods and associated keys. While there are occasional references to genetic separation of taxa, the keys are primarily based on microscope identifications.

Nature and Fauna of the Palaearctic Bioregion

As is clear from the title, this volume covers inland aquatic invertebrates of the Palaearctic, a bioregion that stretches from Iceland in the west to Japan in the east. It also includes inland waters along the Arctic Sea south to northern Africa, the Middle East, and northern China. Taxa in this area occur from low to high altitude sites of varying temperatures, as well as from areas influenced by coastal and inland climatic zones. Unlike our previous books, this volume has extensive coverage of a deep, ancient lake (Lake Baikal) and major inland water saline systems (the Ponto-Caspian region, the Azov Sea, and the Dead Sea). Moreover, the great ecological variation of this bioregion includes hot and cold deserts, temperate steppes, tundra, and forested regions, with concomitant variation in their invertebrate fauna. Many of these diverse habitats are described in Chapter 2 of Volume I. Chapters 2–22 include a comprehensive coverage of the fauna of the Palaearctic, but many poorly studied areas and taxa exist, particularly in central Asia, western China, and Mongolia. The Palaearctic fauna described in this volume overlaps to a minor extent with those in the Nearctic, Afrotropical, and Oriental bioregions and thus with our volumes covering those fauna.

Not all taxa are equally covered in this volume. In some cases, this is intentional, as in limiting Hexapoda to family level (anticipating a large, future volume on insects of this bioregion). In a few other cases (notably with Arachnida), extensive attempts to find qualified authors proved fruitless except for one group. Finally, the taxonomic knowledge of some groups (e.g., Amphipoda) is vastly more extensive than for other taxa as a result of the abundance of invertebrate species and the number of scientists dedicated to studying them.

Components of Taxonomic Chapters

This volume is an identification manual to the inland water invertebrates of the Palaearctic in which we present information needed to diagnose and assign these organisms to various taxonomic levels. Other information concerning ecology, morphology, physiology, phylogeny, and both collecting and culturing techniques can be found in Volume I of this series. Most of the chapters in the current volume are limited to a single phylum. Exceptions are Chapter 2 (multiple kingdoms of protozoa) and the seven chapters on Arthropoda. We have attempted to include the following six sections in each of those chapters: (1) a brief overview of the higher level taxon; (2) a description of identification limitations for each taxon; (3) details of pertinent terminology and morphology; (4) information on preparing and preserving specimens for identification; (5) taxonomic keys (separated by level of identification); and (6) a shortened list of references. Readers can find a much more extensive list of references to their group in Volume I (Chapters 3 and 7–41) along with more details on collecting, preparation, and preserving major taxa. Figures in each chapter are limited to those needed for effective use of the keys. For additional anatomical information, including figures, see the relevant chapter in Volume I.

How to Use This Volume

There is an old maxim that says, keys are written by people who do not need them for people who cannot use them. Nonetheless, we have made every effort to make these keys as user friendly as publication limitations would permit.

Each chapter includes a basic introduction to the morphology and terminology used in diagnosing the taxa of that section. Limitations to the current state of taxonomic knowledge are also presented so that the reader may gauge the reliability of the information presented. Only the established, peer-reviewed scientific literature is used to define the taxonomic categories and epithets included. All names, as far as we are aware, conform to the International Code of Zoological Nomenclature. All nomina and taxonomic arrangements used, as well as the rejection of old names are based on peer-reviewed scientific literature. Names from unpublished manuscripts, dissertations, in-house designations, or records that have not been validated are not included. Provisional names and species designated taxon 1 or species 1 are not used unless they were previously recognized and accepted in the peer-reviewed scientific literature (Richards & Rogers, 2011). No new species descriptions or previously unpublished taxonomic arrangements are presented.

The keys are dichotomous (no triplets or quadruplets are used) and are hierarchical. Thus, for a given group, the first keys are to the highest taxonomic category. The second set of keys is to the next level, the third set to the level below that one, and so on, down to the lowest justifiable taxonomic level based on current knowledge of that group. This level is different for different groups depending upon the state of resolution in the scientific literature. Organisms not identifiable beyond a particular taxonomic level are left at that level.

Properly prepared keys typically employ specific, primary, diagnostic characters. Older keys often use different characters than the more recent keys. This shift in primary characters results from systematists and taxonomists testing the importance of characters. The ultimate goal of the systematist is to have the taxonomic characters used in our keys converge as closely as possible with biological reality. To a nontaxonomist, the resulting process may erroneously seem merely to be lumping and splitting taxonomic groups rather than the result of employing the scientific method to reveal natural relationships.

Surprisingly, many users do not know how to interpret a dichotomous key, making the fundamental assumption that a correct identification answer is always present in the key. This assumption generally takes one of the following three forms:

1. All species are identifiable using a given key. Many new species have yet to be discovered, let alone described. Generalized geographic ranges are provided for most taxa presented herein, yet species ranges shrink, swell, and change elevation constantly, particularly as weather and climate patterns shift. Species disperse, colonize, and suffer stochastic local extinctions. In addition to these natural processes, some species are introduced intentionally or accidentally by humans, and sometimes their establishment allows other species to invade as well. Furthermore, some regions are better studied than others; many parts of the world have not been explored, nor the fauna described. There are still plenty of new taxa to encounter.

2. All variation is accounted for in the key. As stated earlier, identification keys use specific, primary, diagnostic characters. Problems in identification are compounded by taxa that: (1) have different character states at different times; (2) only have diagnostic characters at certain life stages or in certain genders; and/or (3) have severely truncated morphology (often due to lack of sexual selection) and lack morphological characters to separate the species. Furthermore, new variation within taxa is continually developing, and thus one cannot assume that species are immutable or develop tools predicting those changes.

3. The key is a sufficient identification tool in and of itself. A key is just a tool. The fact that one has a bolt that needs removing and a wrench of the correct size does not mean that the bolt can be loosened. Similarly, identification keys are tools to aid in taxon identification. They are primarily tools to eliminate incorrect taxa from the range of possible choices, narrowing the field to the names that may be applicable. Keys are the process of elimination. The possibility that the specimen to be identified is new, a hybrid, anomalous, or a recent invasive colonist is always a possible answer. This is fundamental to using any identification key.

Once one arrives at a name or group of possible names for a specimen in hand, the specimen should then be compared against descriptions, distribution maps, and figures of that and other taxa in that group. The descriptions, figures, and maps are other tools to be used in identification. Direct comparison of the specimen at hand with identified museum material or using molecular comparisons is also sometimes necessary for correct identification.

Species are not immutable, fixed in location and form. They change constantly and will continue to do so, confounding keys and any other identification method, such as trait tables, character matrices, or even genetic analyses. This is why biology is far behind physics in the development of unified theories; biology is far more complex than physics, as it involves more mutable interacting parts and processes.

Keys to Major Taxa of Inland Water Invertebrates of the Palaearctic

A major change in the identification keys for our fourth edition has been to include multiple keys per chapter that generally start with a class-level key and proceed to finer and finer divisions. These allow users to work at their levels of interest, need, and skill without having to wade through extraneous taxa not in the direct line to the taxon of interest.

The following key was derived in part from Chapter 1 in Volume I of the fourth edition. It is meant to allow you to move to the next level of keys, which will be in individual chapters.

1Multicellular, heterotrophic organisms as individuals or colonies (sometimes with symbiotic autotrophs) ………………………… kingdom Animalia ………………………… 2

1′Unicellular (or acellular) organisms present as individuals or colonies with nuclei irregularly arranged; heterotrophic and/or autotrophic; multiple phyla within the autotrophic protozoa phyla ………………………… kingdom Protista [Chapter 2]

2(1)Radially symmetric or radially asymmetric organisms living individually or in colonies ………………………… 3

2′Individuals bilaterally symmetric ………………………… 4

3(2)Surface not porus; oral tentacles always present around a closeable mouth; colonial or single, mostly single polyp forms (primarily hydra) or rarely medusoid form (freshwater jellyfish; adults with a single central body cavity opening to the exterior and surrounded by cellular endoderm, acellular mesoglea, and cellular ectoderm ………………………… phylum Cnidaria [Chapter 4]

3′Surface porus; colonial; tentacles absent; no closable orifices; without discrete organs; cellular-level (or incipient tissue-level) construction; variable, nondistinct colony shapes, including encrusting, rounded, or digitiform growth forms; skeleton of individual siliceous spicules and a collagen matrix; internal water canal system; may contain symbiotic algae; the sponges ………………………… phylum Porifera [Chapter 3]

4(2)Oral region with numerous tentacles or cilia distributed around the mouth; organism never with eversible jaws and never vermiform as adult ………………………… 5

4Oral region with two or no tentacles, or tentacles behind the mouth ………………………… 7

5(4)Oral region with tentacles, organisms in gelatinoids or branching colonies ………………………… 6

5′Oral region ringed with cilia, muscular pharynx (mastax) with complex set of jaws; single free swimming, or semi-sessile living singly or in small colonies; wheel animals, or rotifers ………………………… phylum Rotifera [Chapter 8]

6(5)Oral tentacles (the lophophore) in a U or horseshoe shape around mouth; anus opens outside of lophophore; colonial animals, often in massive colonies attached to hard surfaces; true bryozoans ………………………… phylum Ectoprocta (Bryozoa) (Chapter 13)

6′Both mouth and anus open within lophophore; individual (noncolonial) animals with a calyx containing a single whorl of 8–16 ciliated tentacles ………………………… phylum Entoprocta [Chapter 14]

7(4)Not with the combination of characteristics described below ………………………… 8

7′Small (50–800μm), spindle- or tenpin-shaped, ventrally flattened with a more or less distinct head bearing sensory cilia; cuticle usually ornamented with spines or scales of various shapes; posterior of body often formed into a furca with distal adhesive tubes; gastrotrichs (pseudocoelomates) ………………………… phylum Gastrotricha [Chapter 7]

8(7)Anterior mouth and posterior anus present ………………………… 9

8′Flattened or cylindrical, acoelomate worms with only one ventral digestive tract opening; sometimes with evident head; turbellarian flatworms (commonly called planaria, a nonspecific, and usually incorrect name) ………………………… phylum Platyhelminthes [Chapter 5]

9(8)Vermiform or not, eversible oral proboscis not present, although eversible jaws or other mouthparts may occur ………………………… 10

9′Long, flattened, unsegmented worms with an eversible proboscis; ribbon worms ………………………… phylum Nemertea [Chapter 6]

10(9)Body not enclosed in a single, spiraled shell or in a hinged, bivalved shell; or if a bivalved shell is present, then animal has jointed legs ………………………… 11

10′Soft-bodied coelomates whose viscera is covered (in freshwater species) by a single or dual (hinged), hard calcareous shell; with a ventral muscular foot; fleshy mantle covers internal organs; snails, clams, and mussels ………………………… phylum Mollusca [Chapter 11]

11(10)Segmented legs absent in all life stages; if jaws are present, then body with at least 20 segments ………………………… 12

11′Adults and most larval stages with legs; if larvae are without legs or prolegs (some insects), then cephalic region with paired mandibles, or eversible head, always with less than 15 body segments ………………………… 14

12(11)Organism vermiform, not segmented ………………………… 13

12′Organism vermiform or not, body segmented ………………………… phylum Annelida [Chapter 12]

13(12)Body cylindrical, usually tapering at both ends; cuticle without cilia, often with striations, punctuations, minute bristles, etc.; 1 cm long (except family Mermithidae, <6 cm); nematodes, roundworms ………………………… phylum Nemata [Chapter 9]

13′Body with anterior tip normally obtusely rounded or blunt, posterior tip may be bi- or trilobed; cuticle opaque to dark brown or black, and epicuticle usually crisscrossed by minute grooves; length several cm to 1m, width 0.25–3mm; only adults with free-living stage; hairworms or horsehair worms ………………………… phylum Nematomorpha [Chapter 10]

14(11)Four pairs of clawed, nonjointed legs; water bears ………………………… phylum Tardigrada [Chapter 15]

14′Adults and most larvae with jointed legs, or legs lacking, or more or less than four pairs ………………………… phylum Arthropoda [Chapter 16]²

References

Ahyong, S.T., D.C. Rogers & J.H. Thorp. 2020. Keys to Australasian Fauna. Volume VI in: Thorp and Covich's Freshwater Invertebrates. Fourth Edition. Academic Press, Elsevier, Boston, MA. (In Preparation).

Damborenea, C., D.C. Rogers & J.H. Thorp. 2019. Keys to Neotropical and Antarctic Fauna. Volume V in: Thorp and Covich's Freshwater Invertebrates, Fourth Edition. Academic Press, Elsevier, Boston, MA. (In Preparation).

Hamada, N., J.H. Thorp & D.C. Rogers. 2018. Keys to Neotropical Hexapoda. Volume III in: Thorp and Covich's Freshwater Invertebrates, Fourth Edition. Academic Press, Elsevier, Boston, MS. 811 p.

Richards, A.B. & D.C. Rogers. 2011. Southwest Association of Freshwater Invertebrate Taxonomists (SAFIT) list of freshwater macroinvertebrate taxa from California and adjacent states including standard taxonomic effort levels. 266 p.

Thorp, J.H. & D.C. Rogers (eds.). 2015. Ecology and General Biology. Volume I in: Thorp and Covich’s Freshwater Invertebrates, Fourth Edition. Academic Press, Elsevier, Boston, MA. 1118 p.

Thorp, J.H. & D.C. Rogers (eds.). 2016. Keys to Nearctic Fauna. Volume II in: Thorp and Covich’s Freshwater Invertebrates, Fourth Edition. Academic Press, Elsevier, Boston, MA. 740 p.

---

¹  This chapter was written to be a useful starting point for the previous, current, and future taxonomic volumes in all zoogeographic regions. Consequently, there will be only minor to moderate differences in this chapter among various volumes.

²   Chapter 16 includes a key that will lead to subsequent chapters covering this phylum.

Part I

Outline

Chapter 2. Protozoa

Chapter 3. Phylum Porifera

Chapter 4. Phylum Cnidaria

Chapter 5. Phylum Platyhelminthes

Chapter 6. Phylum Nemertea

Chapter 7. Phylum Gastrotricha

Chapter 8. Phylum Rotifera

Chapter 9. Phylum Nematoda

Chapter 10. Phylum Nematomorpha

Chapter 11. Phylum Mollusca

Phylum Annelida

Chapter 13. Phylum Ectoprocta

Chapter 14. Phylum Entoprocta

Chapter 15. Phylum Tardigrada

Chapter 2

Protozoa

Alan Warren     Department of Life Sciences, Natural History Museum, London, United Kingdom

Genoveva F. Esteban     Bournemouth University, Faculty of Science and Technology, Department of Life and Environmental Sciences, Dorset, United Kingdom

Abstract

Protozoa are a diverse group of separate lineages of single-celled organisms representing almost all the major eukaryote clades. Protozoa typically measure 5 -1000 μm in size. All free-living protozoa need water to survive, hence being essentially aquatic and thriving in freshwater (including soil), brackish, and marine habitats. There is considerable morphological and physiological diversity within the group. The aim of this chapter is to describe and illustrate the families of the main functional groups of the free-living protozoa: the amoeboid, the flagellated and the ciliated protozoa.

Keywords

Amoebae; Flagellates; Ciliates; Eukaryotic micro-organisms; Biodiversity

Chapter Outline

Introduction

Limitations

Terminology and Morphology

Flagellates

Choanoflagellates

Bicoecids

Kinetoplastids

Cryptomonads

Dinoflagellates

Chrysophytes

Euglenids

Amoebae

Heliozoans

Ciliates

Karyorelictea

Nassophorea

Prostomatea and Litostomatea

Phyllopharyngea

Colpodea

Oligohymenophorea

Material Preparation and Preservation

Isolation

Cultivation

Preservation

Acknowledgments

Keys to Protozoa

Protozoa: Major Functional Groups

Protozoa: Major Groups of Flagellated Protozoa

Protozoa: Major Groups of Amoeboid Protozoa

Protozoa: Amoeboid Protozoa: Heterolobosea: Schizopyrenida: Families

Protozoa: Amoeboid Protozoa: Heterolobosea: Lobosea: Families

Protozoa: Amoeboid Protozoa: Cercozoa: Subphyla

Protozoa: Amoeboid Protozoa: Cercozoa: Filosa: Families

Protozoa: Amoeboid Protozoa: Cercozoa: Endomyxa: Families

Protozoa: Amoeboid Protozoa: Granuloreticulosea

Protozoa: Amoeboid Protozoa: Heliozoa and Pseudoheliozoa

Protozoa: Ciliophora: Classes and Subclasses

Protozoa: Ciliophora: Suctoria: Orders

Protozoa: Ciliophora: Suctoria: Exogenida: Families

Protozoa: Ciliophora: Suctoria: Endogenida: Families

Protozoa: Ciliophora: Suctoria: Evaginogenida: Families

Protozoa: Ciliophora: Oligohymenophorea: Peritrichia: Mobilida: Families

Protozoa: Ciliophora: Oligohymenophorea: Peritrichia: Sessilida: Families

Protozoa: Ciliophora: Colpodea: Families

Protozoa: Ciliophora: Oligohymenophorea: Subclasses

Protozoa: Ciliophora: Hymenostomatia: Families

Protozoa: Ciliophora: Peniculia: Families

Protozoa: Ciliophora: Scuticociliatia: Families

Protozoa: Ciliophora: Litostomatea: Orders

Protozoa: Ciliophora: Litostomatea: Pleurostomatida: Families

Protozoa: Ciliophora: Litostomatea: Haptorida: Families

Protozoa: Ciliophora: Prostomatea: Orders

Protozoa: Ciliophora: Prostomatea: Prorodontida: Families

Protozoa: Ciliophora: Prostomatea: Prostomatida: Families

Protozoa: Ciliophora: Nassophorea: Families

Protozoa: Ciliophora: Phyllopharyngea: Families

Protozoa: Ciliophora: Spirochotrichea: Stichotrichia: Orders

Protozoa: Ciliophora: Spirotrichea: Stichotrichia: Sporadotrichida: Families

Protozoa: Ciliophora: Spirotrichea: Stichotrichia: Urostylida: Families

Protozoa: Ciliophora: Spirotrichea: Stichotrichia: Stichotrichida: Families

Protozoa: Ciliophora: Spirotrichea: Hypotrichia: Families

Protozoa: Ciliophora: Plagiopylea: Families

Protozoa: Ciliophora: Spirotrichea: Choreotrichia and Oligotrichia Families

Protozoa: Ciliophora: Armophorea: Families

Protozoa: Ciliophora: Heterotrichea: Families

References

Introduction

During the last 20 years, studies on the systematics and evolution of unicellular eukaryotes (algae, protozoa, and lower fungi) have been in a state of great activity. Over this period, many taxonomic boundaries, including those between the algae and protozoa, have been broken down and new relationships established (Cavalier-Smith, 2010; Adl et al., 2012; Ruggerio et al., 2015). As a result, the constituent organisms are grouped together by some workers as protists, reviving the term originally coined by Haekel (1866), or as protoctists (Margulis et al., 1989), although many systematists believe that such groups have no evolutionary or systematic validity. By contrast, other workers have proposed systems that retain the kingdom Protozoa, albeit with much modified definitions and boundaries (Cavalier-Smith, 2010; Ruggerio et al., 2015). Nevertheless, the terms algae and protozoa are still useful in a functional or ecological sense defining (primarily) photoautotrophic and heterotrophic protists, respectively.

Protozoa sensu lato, which means first animals, are a diverse assemblage that comprises a number of separate lineages representing almost all the major eukaryote clades, including alveolates, stramenopiles, amoebozoans, opisthokonts, rhizarians, and excavates (Cavalier-Smith, 2010; Adl et al., 2012; Ruggerio et al., 2015). Protozoa typically measure 5–1000   μm in size, and most are visible only with the aid of a microscope. There is considerable morphological and physiological diversity within the group. Because actively feeding protozoa need water, all free-living (nonparasitic) protozoa are essentially aquatic, living in freshwater (including soil), brackish, and marine environments.

Limitations

There are a number of factors that pose significant limitations to the taxonomy of protozoa. These include: (1) the lack of adequate methods for the fixation and long-term preservation of specimens for much of the ca. 350-year history of the discipline of protozoology; (2) an absence of type specimens for most species; (3) a lack of sufficient morphological features for species circumscription; (4) inadequate species descriptions for reliable identification; (5) high rates of synonymy; (6) insufficient numbers of trained taxonomists; (7) undersampling and a large unknown species diversity; and (8) technical difficulties in culturing many species, which is sometimes a prerequisite for adequate characterization.

It is often difficult and time-consuming to identify protozoa to the level of species. In many cases, unambiguous identification requires specialized staining techniques or the use of electron microscopy. The taxonomic grouping used in our key is an amalgamation of publications by specialists on the different groups (e.g., Lee et al., 2000; Lynn, 2008; Bass et al., 2009; Cavalier-Smith, 2010; Smirnov et al., 2011; Adl et al., 2012; Ruggerio et al., 2015). While the taxonomy of many groups is based on a combination of cell morphology, ultrastructural features, and molecular data, this key is designed to make possible the identification of many protozoa to the family level using light microscopy alone. Although observation of living organisms is important for identification, the key should still be useful for many fixed samples. The illustrations used as examples here are of one or more species considered typical of a genus.

Although this key primarily deals with free-living protozoa, some ciliates that are commensal or parasitic (e.g., certain groups of suctorians and oligohymenophoreans) are also included.

Terminology and Morphology

Traditionally, free-living protozoa have been divided into three main groups according to their morphology and means of locomotion: flagellates, amoebae (including heliozoans), and ciliates (Fig. 2.1). Of these, only the ciliates are a truly natural, monophyletic group. The flagellates and amoebae are polyphyletic and include groups that may be only distantly related. Nevertheless, from a practical viewpoint, it is still sometimes useful to refer to these groupings because isolation, cultivation, and identification methods used are often the same within each group.

Figure 2.1 Examples of the main functional groups of protozoa. (A) Peranema trichophorum – a flagellate; (B) Amoeba proteus – an amoeba; (C) Actinophrys sol – a heliozoan; (D) Tetrahymena sp. – a ciliate. 

After Vickerman & Cox (1967) (A and B); From Siemensma, Ferry J.; Page, F. C., Nackte rhizopoda und heliozoea, 1991. (C); Curds (1982).

Flagellates

Flagellates are characterized by the possession of one or more flagella, which are long, tapering, hair-like appendages that act as organelles of locomotion and feeding (Figs. 2.1 A and 2.19 B). In free-living taxa, as opposed to parasitic species, the number of flagella is limited; Paramastix has two rows of 8–12 flagella, but most others have 1–4 (usually 2). Where two flagella are present, one typically projects forward and the other trails behind. Often, the organism's flagella are longer than its body. There are several groups of heterotrophic flagellates in fresh water: choanoflagellates, kinetoplastids, diplomonads, and bicoecids. These are raised to phyla by some authors, while bicoecids are occasionally put with chrysophytes. Some amoeboid forms such as cercomonads and the Schizopyrenida, or amoeboflagellates, also have flagella but are treated here with the amoebae.

Other groups of flagellates contain mostly or entirely autotrophic forms with chloroplasts. However, many of the pigmented, autotrophic taxa are also capable of phagotrophy, producing an overall condition called mixotrophy (Sanders, 1991; Esteban et al., 2010), and also among these groups are some wholly heterotrophic species. The groups with many mixotrophic or heterotrophic taxa include cryptophytes, chrysophytes, dinoflagellates, and euglenoids and are usually considered phyla. Pigmentation and chloroplast morphology are important taxonomic characters for some of these groups.

Choanoflagellates

These collared flagellates, are distinctive for the collar that surrounds the single flagellum (Figs. 2.2 B–H). They bear a strong resemblance to sponge choanocytes. Most choanoflagellates attach to the substrate or are colonial, and many have an external, loose-fitting covering or lorica, although this may be difficult to see with the light microscope.

Bicoecids

These protozoa (Fig. 2.2 I) resemble choanoflagellates, although they lack a collar. Like choanoflagellates, they are enclosed in a lorica and have a flagellum that is used to create a feeding current. A second flagellum lies along the cell and continues posteriorly to become an attachment to the base of the lorica.

Kinetoplastids

Kinetoplastids (Figs. 2.2 J, N–P) are known mostly as parasites, especially Trypanosoma and its relatives, but many members of the suborder Bodina live in fresh water (Vickerman, 1976). The best-known genus is Bodo, which, like other bodonids, has two flagella (Fig. 2.2 J), one of which trails, while the other extends ahead.

Cryptomonads

The cryptomonads include many common heterotrophs and autotrophs and a few mixotrophs. The two flagella are unequal in length and arise from a subapical invagination commonly referred to as a gullet, although it does not appear to be the site of ingestion in heterotrophic forms. The pellicle is covered with plates, although these also are not generally visible.

Dinoflagellates

Dinoflagellates (Figs. 2.3 A–C and 2.19 C) form a very large and unique group that is probably more important in marine than freshwater environments. Their unique arrangement of flagella, one spiraling around the cell in a groove (girdle) and a second distally directed in another groove (sulcus), makes them distinctive. Again, heterotrophy and mixotrophy are common. A covering of plates may or may not be present (hence the terms armoured and naked dinoflagellates).

Chrysophytes

The generally small organisms prey on bacteria. They have two unequal flagella, one long and directed anteriorly, the other short and directed laterally (Figs. 2.3 K–M). They are naked or covered in fine siliceous scales (Esteban et al. 2012), which are not always visible with light microscopy; many are amoeboid. Their carbohydrate storage product, chrysolaminarin, occurs in liquid globules and may be useful in recognizing the members of this group. Chrysophytes contain both colorless heterotrophs and pigmented mixotrophs.

Euglenids

Euglenids are generally large flagellates with two flagella, although in many taxa only one flagellum emerges from the gullet (Fig. 2.3 D). Several heterotrophic species creep over the substrate with the second flagellum trailing and hidden beneath the cell (Figs. 2.3 F–H), as in some bodonids. The euglenids are currently assigned to the supergroup Excavata (Adl et al. 2012; Ruggerio et al., 2015).

Amoebae

The primary characteristic of amoebae is their possession of pseudopodia, retractile processes that serve as organelles of locomotion and feeding (Figs. 2.1 B and 2.19 A). There is considerable diversity of structure in the amoebae, particularly in the character of any shell or skeletal material that may be present, and in the type of pseudopodium, for example, broadly lobed, needle-like, or reticulate. Amoebae range in size from only a few micrometers to 2   mm in diameter. Although many lack a fixed external morphology, the characteristic morphologies shown by the various taxa are surprisingly distinctive even if difficult to quantify (Fig. 2.4). By using also the number, size, and structure of organelles and characteristics of tests (where present), identification is not as difficult for living specimens as might be imagined. The morphology of amoebae is plastic. Many adopt a stellate morphology if suspended in water, but few are truly planktonic, rather they live on surfaces or in sediments. In most Amoeba (Figs. 2.1 B and 2.4 F), for example, the cytoplasm is divided into an inner granular endoplasm and an outer hyaline ectoplasm, or hyaloplasm, with a characteristic thickness and distribution around the cell. Locomotion may be achieved by extending many pseudopodia simultaneously, as in Amoeba (Figs. 2.1 B and 2.4 F), or by moving as a single mass on a broad front (Figs. 2.4E, P), or as a cylinder (limax amoebae, Figs. 2.4 I, K, L). Not only do pseudopodia have characteristic shapes but the tail end or uroid may be distinctive (Figs. 2.4 J, L), and the cell surface may be distinctly sculptured, as in Thecamoeba (Fig. 2.4 D). The classification and systematics of the naked, lobose amoebae were recently revised by Smirnov et al. (2011) and Cavalier-Smith et al. (2015).

Figure 2.2 (A) Uroglena americana (mixotrophic); (B) Desmarella moniliformis; (C,D) Sphaeroeca volvox, individual and colony; (E) Codosiga botrys; (F) Diploeca plactita; (G) Salpingoeca fusiformis; (H) Monosiga ovata; (I) Bioeca lacustris; (J) Bodo caudatus; (K) Cercomonas sp.; (L) Cephalomonas cyclopum; (M) Hexamita inflata; (N and O) Pleuromonas jaculans, attached and amoeboflagellate forms; (P) Rhynchomonas nasuta. 

After: Bourelly (1968) (L); Calaway and Lackey (1962); (N, O, and P) Lackey (1959); (B and F) Lee et al. (1985); (K); Pascher (1913) (C, D, E, G–J, and M). Scale 5 2.5   μm for P; 5   μm for (F, G–I, K, and L); 10   μm for (A–C, J, and M–O); and 20   μm for (E).

Figure 2.3 (A) Peridinium; (B) Gymnodinium; (C) Gyrodinium; (D) Khawkinea halli; (E) Polytomella citri; (F) Entosiphon sulcatum; (G) Petalomonas abcissa; (H) Peranema trichophorum; (I) Spumella (Monas) vivpara, two cell shapes; (J) Chilomonas paramecium; (K) Paraphysomonas vestita; (L) Spumella (Monas) vivipara, two cell shapes; (M) Ochromonas variabilis a; (N) Dinobryon sertularia (mixotrophic). 

After: Bourelly (1968) (L); Calaway and Lackey (1962) (E, F, J, and N); Eddy (1930) (A); Jahn and McKibben (1937) (D); Leedale (1985) (H); Pascher (1913) (M); Lemmerman (1914) (K); Shawhan and Jahn (1947) (G); Smith (1950) (I). Scale 5   μm for (E); 10   μm for (A–C, G, and I–M); and 20   μm for (D, F, H, and N).

Figure 2.4 (A) Vahlkampfia avaria; (B) Naegleria; (C) Stachyamoeba lipophora; (D) Thecamoeba sphaeronucleolus; (E) Vanella miroides; (F) Amoeba proteus; (G) Mayorella bigomma; (H) Vexillifera telemathalassa; (I) Hartmannella vermiformis; (J) Chaos illinoisense; (K) Saccamoeba lucens; (L) Trichamoeba cloaca; (M) Echinamoeba exudans; (N) Acanthamoeba; (O) Filamoeba nolandi; (P) Hylodiscus rubicundus. 

After: Bovee (1985) (A–D, H–J, and M–P); Kudo (1966) (F); Page (1988) (E, G, K, L, and P). Scale 5–10   μm for (A–C, E, I, and M); 15   μm for (H and N–P); 30   μm for (D, G, K, and L); 50   μm for (F); and 100   μm for (J).

Other groups of amoebae, notably the testate amoebae, possess shells (or tests) that may be proteinaceous, agglutinate, siliceous, or calcareous in composition (Figs. 2.5 A–Q, 2.6 B–K and 2.9 H). These are generally vase-shaped, with a single opening through which pseudopodia emerge. Many are terrestrial, but benthic forms are common, and a few are planktonic. Identification of testate amoebae is mainly based on shell characters, i.e., size, shape, and composition.

Heliozoans

Heliozoans and pseudoheliozoans are roughly spherical amoebae with many stiff projections called axopodia radiating outward from the cell surface (Figs. 2.1 C, 2.7 and 2.8 D, E, I, J, L). The axopodia give heliozoans their characteristic sun-like appearance for which they are named, and are variously used for capturing food, sensation, movement, and attachment. Axopodia are strengthened by a microtubular array called an axoneme or stereoplasm. The term axoneme is also used to describe the microtubular core of cilia and flagella, but this does not imply homology and the origin and ultrastructure of axonemes is diverse (Yabuki et al., 2012). Most heliozoans lack the skeleton that is so characteristic of their marine counterparts such as Radiolaria and Acantharia, although some are covered in siliceous or organic scales (Figs. 2.7 F, H), and some have a perforated shell or capsule (order Desmothoracida, Fig. 2.7 A). Although heliozoans are frequently planktonic, they are found primarily on or near the benthos. Some heliozoans traverse the bottom with a unique tumbling motion resulting from controlled changes in the length of the axopodia. Many sessile forms with stalks are known. In sessile forms, cell division is likely to be unequal, producing a dispersal stage that may be flagellated or amoeboid. For a modern treatment of the taxonomy of heliozoans, see Cavalier-Smith and von der Heyden (2007).

Figure 2.5 (A) Cochliopodium bilimbosum; (B and C) Phryganella nidulus, side and oral views; (D) Pyxidicula operculata; (E) Plagiopyxis callida; (F and G) Arcella vulgaris, side and dorsal views; (H and I) Penardochlamys arcelloides, side and oral views; (J and K) Difflugia corona, side and oral views; (L and M) Hyalosphenia cuneata; (N) Lesquereusia spiralis; (O and P) Quadrulella symmetrica; (Q) Nebela collaris; (R) Penardia granulose; (S) Chlamydophrys minor; (T and U) Lecythium hyalinum, dorsal and side views; (V) Pelomyxa palustris; (W) Pseudo-difflugia gracilis. 

After: Bovee (1985) (A–C, H–K, N–P, R, T, and U); Deflandre (1959) (D–G, L, M, Q, S, and W); Kudo (1966) (V). Scale 5–10   μm for (C, R, and S); 30