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NUTRITION AND FEEDING STRATEGIES IN
PROTOZOA
Nutrition and Feeding
Strategies in Protozoa
Brenda Nisbet, BSc, PhD.
Department of Zoology,
University of Aberdeen,
Scotland
CROOM HELM
London & Canberra
© 1984 Brenda Nisbet
Softcover reprint of the hardcover 1st edition 1984
Croom Helm Ltd, Provident House, Burrell Row,
Bcckenham, Kent BR3 1AT
Croom Helm Australia, PO Box 391,
Manuka, ACT 2603, Australia
Croom Helm Australia Pty Ltd,
28 Kembla Street, Fyshwick,
ACT 2609, Australia
British Library Cataloguing in Publication Data
Nisbet, Brenda
Nutrition and feeding in protozoa.
1. Protozoa
1. Title
593.1 '041'3 QL366
ISBN-13: 978-94-011-6557-0 e-ISBN-13: 978-94-011-6555-6
001: 10.1007/978-94-011-6555-6
Biddies Ltd, Guildford and King's Lynn
CONTENTS
1. Introduction
2. Environments and Ecosystems: Freshwater and Marine 13
3. Environments and Ecosystems: Soils, Biological
Purification Systems and Other Animals 40
4. Autotrophic Nutrition 71
5. Heterotrophic Feeding 84
6. Endocytotic Vacuoles in Digestion 101
7 Metabolic Pathways 114
8. Feeding in the Ciliophora 128
9. Variety in the Mastigophora 156
10. Sarcodina 185
11. Apicomplexa 202
12. Myxozoa, Microspora and Ascetospora 219
13. Inter-relationships in Protozoan Communities 232
Bibliography 248
Index 274
1 INTRODUCTION
Modern biologists describe protozoa as microscopic eukaryotic organ
isms with a capacity for establishing themselves in almost every con
ceivable habitat provided it contains moisture in some form. In 1674
at the time when Antony von Leeuwenhoek was making his first
observations of 'very small animalcules' in Berkelse Mere near his
home town of Delft, this concept of the ubiquity of protozoa would
have been difficult to comprehend. Leeuwenhoek's curiosity later led
him to examine the body fluids, gut contents and excreta of different
animals and to describe 'an inconceivably great company of living
animalcules, and these of divers sorts and sizes'. Here were early des
criptions of parasitic protozoa, species which later came to be recog
nized as Opalina, Giardia, Trichomonas and others. Following his
pioneering work in the field of microscopic observation, knowledge of
protozoa has accumulated at an accelerating pace. Some 30,000 living
species have been identified, and an equal number of fossil species,
from habitats which range from the ocean waters to the exuvial fluid of
insects. The study of protozoan nutrition is a particularly interesting
aspect of this expanding field of zoology. What kind of nourishment do
protozoa need, how do they acqlire it, and what influence do the
answers to these two questions havE on where protozoa live?
The need to determine what hId of food protozoa are utilizing in
their environment is desirable in al ecological studies involving micro
organisms of aquatic communities. The ways and means of acquiring
this information are difficult in practice. Laboratory cultures show
what food is acceptable, but this dOI:s not necessarily reflect the natural
food choice nor the food choice in the habitat under investigation. In
some of the larger ciliates and am(lebae it is possible to identify the
contents of the food vacuoles in freshly-collected samples, but as
Fenchel (1968) noted, vacuole cont~nts very rapidly become unrecog
nisable except for the siliceous frust ules of diatoms which retain their
integrity.
Feeding Mechanisms
The ways in which protozoa acquin their food, by hunting, by para-
N ~ g ~ '"' ~. ;:::
m y.
me etle
gh the pellicle and a ciliary Electron micrograph by L. T ellicular microtubules. / A/'// --=-I~~/ ~" .. _ .-0 ... --~ > 2C > ~ d'" r.• @",i.';'!i.{/,"··;:::····,·· I ~,~~~' ?';:.~~ ---~p .. _."
uplotes. (a) Section throu and linking microtubules. nd ventral patterns of subp .' I;-~ 55:;;> ./""'-Y":> l=~--'--- (b)
E s a
of me sal
e so or
r o d
atu net he
nfracili heir ki on of t
bpellicular I cilia with t reconstructi
he Cilia and Su of three s rows A diagrammatic n Grim (1967).
1.1: T e show 00. (b) Based o
Figure branell X 20,0 (a) Source:
Introduction 3
sitizing, by some form )f scooping or vacuum-like suction, by chance
contact or by photosynlhesis will be discussed in later chapters. There
is considerable uniformity in feeding behaviour within genera but this
must not be assumed as 1 general rule. Feeding strategies depend partly
on the potential for mOl phological adaptation which itself is related to
the organization of the g ·oup. This point can be illustrated by consider
ing a group such as the ciliates which show a wide range of morpho
logical features based c n the possession of cilia and the elaborate
arrangement of microfillments and microtubules which co-ordinate
ciliary activity (Figure t.1; and Corliss, 1979; Grell, 1973; Sleigh,
1973). The pattern of r, licrofilaments linked to kinetosomes (ciliary
basal bodies), which lies internal to the pellicle of a ciliate, makes up
the infraciliature, now recognized as being of crucial importance in the
study of protozoan relationships and evolution (Corliss, 1979). In spite
of having an efficient, c.osely-structured infraciliature, the organism
which depends on cilia for food trapping and movement is automatic
ally restricted in both the ;ize and type of food which can be taken.
The most generally acce pted types of food - bacteria, algae and other
small organisms - for free ·living protozoa, are not specific to anyone
environment nor are they ingested by anyone standard method. A
ciliate uses ciliary current~ to draw a stream of yeast cells towards its
mouth; an amoeba engul1 s yeast cells by pseudopodial flow and a
flagellate may use its fla ~ellum and a rod-like ingestion organelle.
Different feeding strategie.: employed towards one type of food are
illustrated in Figure 1.2.
The different food-trat ping strategies just described are simply
versions of small particle -eeding in the broad scheme compiled by
Yonge (1928, 1954). Yonfe has three categories of feeding mechan
isms based on particle size (If food taken, which encompass all animals
except the vertebrates. All 1 hree mechanisms, for trapping small parti
cles, for engulfing large parl icles or whole organisms and for taking in
fluids or soft tissues, may be found in protozoa (Table 1.1).
It will become evident, I'articularly from Chapters 8-12, that pro
tozoan feeding mechanism: spread through these three categories
irrespective of taxonomic re lationships: 'Feeding mechanisms develop
in correlation with the envi ronment and the available food and any
classification of them must cut clean across the subdivisions of the
animal kingdom' (Yonge, 1928).
Even accepting this wide range of feeding mechanisms, it becomes
clear that protozoa occupy, unique position in the biological world,
because although the majorit~· are structurally and nutritionally similar
4 Introduction
Figure 1.2: Different Food-trapping Strategies towards One Type of
Particulate Food (Yeast Cells). (a) Paramecium uses ciliary currents
and an oral groove; (b) Peranema uses a probing flagellum and a rod
organ; (c) Amoeba ingests by pseudopodial flow.
10~m (c)
15~m
