A FUNCTIONAL BIOLOGY OF FREE-LIVING PROTOZOA

A FUNCTIONAL BIOLOGY OF FREE-LIVING PROTOZOA

A Futletiotull Biology ojfree-living Protozoa JOHANNA LAYBOURN-PARRY, BSe, MSc, PhD Department of Biological Sciences, University of Lancaster, Lancaster, UK CROOM HELM London & Sydney

1984 Johanna Laybourn-Parry Softcover reprint of the hardcover 1 st edition 1984 Croom Helm Ltd, Provident House, Burrell Row, Beckenham, Kent BR3 1AT Croom Helm Australia Pty Ltd, First Floor, 139 King Street, Sydney, NSW 2001, Australia British Library Cataloguing in Publication Data Laybourn-Parry, Johanna A functional biology of free-living protozoa. 1. Protozoa I. Title 593.1 QL366 ISBN-13: 978-1-4684-7318-6 DOl: 10.1007/978-1-4684-7316-2 e-isbn-13: 978-1-4684-7316-2 Typeset by Columns of Reading

CONTENTS Series Foreword Preface and Acknowledgements viii ix 1. The Protozoan Cell 11 A. Introduction 11 B. Protozoan Systematics 12 C. Evolution of Protozoa 19 D. Free-living Protozoa 20 (i) Mastigophora - The Flagellates 21 (ii) Sarcodina - The Amoebae 23 (iii) Ciliophora - The Ciliates 26 E. The Protozoan Cell 28 2. How Protozoa Obtain Energy 32 A. Introduction 32 B. Modes of Feeding 33 (i) Protozoa With a Cytostome or Cell Mouth 33 (ii) Protozoa Lacking a Cytostome 48 (iii) Pinocytosis 51 C. Food Selection in Protozoa 52 D. Digestive Processes 54 E. Symbiotic Relationships in Protozoa 59 F. Factors Influencing Feeding 60 3. Physiological Functioning of Protozoa 66 A. Introduction 66 B. Asexual Life-cycle 67 (i) Types of Binary Fission 68 (ii) Mean Cell Volume Variation 75 (iii) Growth and Factors Influencing Growth and Division 78 C. Sexual Reproduction 86 (i) Factors Stimulating Sexual Reproduction 86 (ii) Isogamous Reproduction 88 v

vi Contents (iii) Anisogamous Reproduction 91 D. Respiration 93 (i) Aerobic Respiration 94 (ii) Anaerobic Respiration 104 E. Osmoregulation and Excretion 104 4. Movement 110 A. Introduction 110 B. The Structure of Locomotory Organelles III (i) Ciliophora and Mastigophora III (ii) Sarcodina 117 C. Chemical Basis of Movement 119 (i) Chemical Processes in Cilia and Flagella 121 (ii) Chemical Processes in Amoeboid Movement 123 D. Forms of Locomotion 125 (i) Locomotion in Ciliates and Flagellates 125 (ii) Contractile Movement in Ciliates 130 (iii) Locomotion in Sarcodina 131 E. Factors Influencing Speed of Movement 132 (i) Flagellates 132 (ii) Ciliates 133 (iii) Sarcodina 134 5. Trophic Relations of Protozoa 135 A. Introduction 135 B. Protozoan Energetics 138 (i) The Energy Equivalents of Protozoa and their Food 139 (ii) Energetics 140 (iii) How Protozoa Maximise Net Energy Returns from their Feeding Behaviour 148 C. r K Selection in Protozoan PopUlations 152 D. Interactions of Bacterivorous Protozoa with their Food Source 155 (i) The Impact of Protozoa on their Bacterial Food Source 155 (ii) The Role of Protozoa in Nutrient Recycling 158 E. Predators of Protozoa 161 6. Ecology and Adaptability 164 A. Introduction 164 B. Ecology and Adaptation in the Natural Environment 165 C. Encystment 169

Contents vii D. Protozoa in Sewage Treatment E. The Role of Protozoa in Polluted Ecosystems 7. Conclusions Bibliography Index 177 179 186 188 213

FUNCTIONAL BIOLOGY SERIES: FOREWORD General Editor: Peter Calow, Department of Zoology, University of Sheffield, England The main aim of this series will be to illustrate and to explain the way organisms 'make a living' in nature. At the heart of this - their functional biology - is the way organisms acquire and then make use of resources in metabolism, movement, growth, reproduction, and so on. These processes will form the fundamental framework of all the books in the series. Each book will concentrate on a particular taxon (species, family, class or even phylum) and will bring together information on the form, physiology, ecology and evolutionary biology of the group. The aim will be not only to describe how organisms work, but also to consider why they have come to work in that way. By concentrating on taxa which are well known, it is hoped that the series will not only illustrate the success of selection, but also show the constraints imposed upon it by the physiological, morphological and developmental limitations of the groups. Another important feature of the series will be its organismic orientation. Each book will emphasise the importance of functional integration in the day-to-day lives and the evolution of organisms. This is crucial since, though it may be true that organisms can be considered as collections of gene-determined traits, they nevertheless interact with their environment as integrated wholes and it is in this context that individual traits have been subjected to natural selection and have evolved. The key features of the series are, therefore: (1) Its emphasis on whole organisms as integrated, resource-using systems. (2) Its interest in the way selection and constraints have moulded the evolution of adaptations in particular taxonomic groups. (3) Its bringing together of physiological, morphological, ecological and evolutionary information. This volume, on free-living Protozoa, is the first in the series. viii P. Calow

PREFACE AND ACKNOWLEDGEMENTS One feature of protozoological research which struck me from the beginning of my association with the Protozoa as a researcher, was that the study of these organisms is often divorced from the natural environment. A considerable number of species lend themselves to easy culture in the laboratory and some have become familiar laboratory organisms. There is a wealth of information on such species, which represent only an infinitesimal portion of the representatives of the protozoan subkingdom which inhabit the waters and soils of the world. Inevitably organisms routinely maintained in culture tend to be studied in the context of the laboratory, and although the data generated are interesting and often extremely valuable, they frequently lack an essential component: they tell us very little about the organism as it functions in nature. We can never hope to gain a full understanding of an organism's functional biology unless we consider how the chemical and physical characteristics of its natural environment can modify the performance of essential life processes. There are relatively few free-living organisms which enjoy a constant environment, most face short- or long-term changes in temperature, ph, food supply, oxygen availability, moisture and light. The impact of such variations on the physiology of an organism will to a large extent be a function of its physiological and ecological tolerances, and its adaptability. Thus the ideal approach to the study of the Protozoa should take account of the variable conditions prevailing in the natural environment. Moreover, this approach may ultimately give us an insight into how various patterns of biological function have evolved in the Protozoa. Various people have given me help in the preparation of this book and it is with pleasure that I take this opportunity to thank them. My thanks are due to Christine Martin and Margaret Holden who typed the manuscript, Christine Kingsmill who helped with the bibliography and Ken Oates for his invaluable help with photography. I am particularly grateful to those publishers and authors, acknowledged in detail elsewhere, who allowed me to reproduce graphs and illustrations. Many were kind enough to send me original drawings and photographs. My ix

x Preface and Acknowledgements thanks must also go to those who offered valuable criticism in the preparation of this book and the general editor of the Functional Biology series, Dr Peter Calow, for his guidance.