compiled by

R. A. Davis
Department of Biology
College of Mount St. Joseph
Cincinnati, Ohio


Taxonomic Framework
Generic Index
Background Comments
Key to Symbols and Abbreviations Used in Citations
Audio-visual Materials
Materials Available for Study
Directions for Completing Your Study of This Group of Organisms
About this web-page -- Caveat lector !


The following are comments and other information relating to the protists. This compilation definitely is neither comprehensive or exhaustive. Thus, in addition to the following, you should study as much other material related to the subjects mentioned as you "can get your hands on". To this end, toward the bottom of this WEB-page are listed some bibliographic references that might prove useful. There also is an ankyliography (a list of links) to web-sites that may contain some useful information. If the word you seek is not listed below, please, see whether it is included in the general glossary.

If you have some suggestions as to how this WEB-page might be improved, please, contact me.

R. A. Davis
Professor of Biology and Geology
Department of Biology
College of Mount St. Joseph
Cincinnati, Ohio, 45233-1670, USA

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The higher-level taxonomy amongst the protists is in a state of considerable flux. Different experts champion different schemes of classification. This is due, at least in part, to the small size and, consequent difficulty of study of many protists. Moreover, many new techniques have been brought to bear on the protists in recent years.

Note that some authorities consider that the protists do not comprise a single kingdom, but, rather, that organisms of several kingdoms are involved.

The following is based on the classificatory schemes presented in various publications. However, it may not include all taxa listed therein, because we may not have specimens of all of them for you to study. The various schemes of classification do not always correspond with one another, nor does that presented below correspond exactly (and sometimes not even inexactly) with other classificatory schemes. Moreover, there is no doubt that the scheme presented below will be subject to considerable change in future years.

(Please, recall that botanists tend to use the taxonomic level "Division" for what zoölogists call "Phylum".)


"subkingdom Algae"

phylum Euglenophyta

(present-day forms: Euglena)


phylum Chrysophyta ----- ("Golden-brown algae", "Yellow-green algae")

subphylum Bacillariophyta (the "diatoms")

(for example, Diatoma, Fragilaria, Ochromonas)


phylum Chlorophyta ----- "the green algae”

(present-day forms: Acetabularia, Chara, Chlamydomonas, Chlorella, Cladophora, Gonium, Oedogonium, Pandorina, Spirogyra, Ulothrix, Ulva, Volvox)

(fossil forms: Receptaculites, charophytes [which are egg-bearing structures])


phylum Phaeophyta ----- "the brown algae"

(present-day forms: Ectocarpus, Fucus, Laminaria, Macrocystis [the "giant Pacific kelp"], Sargassum)


phylum Rhodophyta ----- "the red algae"

(present-day forms: Chondrus, Polysiphonia, Porphyra, "coralline algae")


phylum Pyrrophyta (= Dinoflagellata)

(present-day forms: Ceratium, Gonyaulax, Noctiluca, Peridinium, Ptychodiscus bruvis [the dinoflagellate responsible for "red tides"])


"The Slime-Molds"

phylum Acrasiomycota ----- "cellular slime-molds"


phylum Oömycetes ----- "water molds"


phylum Myxomycota ----- "plasmodial slime-molds"

(for example, Physarum)


"subkingdom: Protozoa"

superphylum: Mastigophora (= Flagellata)

phylum: Zoömastigophora

(for example, Trichonympha [obligate endosymbionts of termites], Trypanosoma [different species of which are responsible for "African sleeping sickness" and "Chagas’ disease"])


superphylum: Sarcodina

phylum: Rhizopoda

class: Lobosea

(for example, Amoeba, Difflugia, Entamoeba)


phylum: Foraminifera (= Granuloreticulosa) ----- the foraminiferans


phylum: Actinopoda


class: Heliozoea

(for example, Actinophrys, Actinosphaerium)

classes: Acantharea, Phaeodarea, and Polycystinea ----- "the radiolarians"


superphylum: Apicomplexa

phylum: Sporozoa

(for example, Plasmodium, the organism responsible for malaria, different species for different kinds of malaria)


superphylum: Ciliata

phylum: Ciliophora

(for example, Balantidium, Didinium, Paramecium, Pharmecium, Spirostomum, Stentor, Tetrahymena, Vorticella)

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Listed below are some representative genera of some of the higher taxa.

[Note that some of the names listed are of taxa not, in fact, assigned to the "kingdom" Protista. For example, there are some cyanobacteria listed. This is an historic artifact from times when some of these organisms were thought to be protists.]


higher taxa

Actinophrys Protista, Sarcodina, Actinopoda
Actinosphaerium Protista, Sarcodina, Actinopoda
Amoeba Protista, Sarcodina, Rhizopoda
Anabaena Cyanobacteria
Balantidium Protista, Ciliophora
Chara Protista, Chlorophyta
Chlorobium Eubacteria, Gracilicutes, Chlorobia
Chroococcus Cyanobacteria
Didinium Protista, Ciliophora
Difflugia Protista, Sarcodina, Rhizopoda
Entamoeba Protista, Sarcodina, Rhizopoda
Giardia Protista, Archaeprotista
Gloeocapsa Cyanobacteria
Gloeotrichia Cyanobacteria
Merismopedia Cyanobacteria
Mycoplasma Eubacteria, Tenericutes, Aphragmabacteria
Nitrocystis Eubacteria, Proteobacteria
Oscillatoria Cyanobacteria
Paramecium Protista, Ciliophora
Plasmodium Protista, Apicomplexa, Sporozoa
Polysiphonia Protista, Rhodophyta
Rhizobium Eubacteria, Proteobacteria
Rivularia Cyanobacteria
Spirostomum Protista, Ciliophora
Stentor Protista, Ciliophora
Tetrahymena Protista, Ciliophora
Thiospirillum Eubacteria, Proteobacteria
Trichonympha Protista, Mastigophora, Zoomastigophora
Trypanosoma Protista, Mastigophora, Zoomastigophora
Vorticella Protista, Ciliophora
Zygnema Protista, ? Chlorophyta

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The kingdom Protista was proposed by Ernst Haeckel in 1866 to include all the one-celled organisms. As originally proposed, it included both prokaryotic and eukaryotic organisms. The former comprised the subkingdom Monera, whereas the latter, the subkingdom Protoctista, a name proposed by Hogg in 1860. The name "Protista" means, literally, "very first", because Haeckel had concluded that protists were the first organisms on Earth.

Since that time, of course, it has been recognized that there are more kingdoms than Protista, Animalia (= Metazoa), and Plantae (= Metaphyta). Indeed, the kingdom Protista, as originally understood, includes organisms that some workers assign to at least three separate kingdoms, and the Fungi comprise a separate kingdom.


The phylum Rhizopoda includes amoeba-like protists. They possess moveable extensions of the cytoplasm that are called pseudopodia. (The singular is pseudopodium, or, less formally, pseudopod.) Pseudopodia are used for locomotion and capturing food. (Unlike some other protists, members of the phylum Rhizopoda lack flagella.)


Individuals of some genera each make a case for the bulk of their protoplasm; this is called a test. (Note that the test is not a shell, per se; a shell encloses the soft-parts of the organism and serves for protection, among other functions.)


Most members of the phylum Rhizopoda reproduce asexually by means of fission.

Examples of members of the phylum:

Amoeba includes organisms that live in fresh-water. They are motile and tend to move across the bottom-surfaces of their environment.

Difflugia is a common fresh-water amoeba. Individuals of this genus each collect small mineral particles and make a test that protects the individual;

Entamoeba histolytica causes dysentery in humans; it is a parasitic form.


Members of the genus Amoeba are phagocytic. They engulf particles of food and form a membrane-bound food-vacuole. Enzymes are secreted into the food-vacuole, and digestion, thus, is intracellular.

Osmotic balance:

This is accomplished by contractile vacuoles.



Members of the phylum Foraminifera commonly are called “forams”. They each secrete a test bearing pores that allow the thin pseudopodia to protrude. (The name “Foraminifera” means “hole bearing”.) The test generally is made of calcium carbonate, although individuals of some kinds of forams gather minute mineral particles and “glue” them together to form a test.

Foraminiferans are, of course, one-celled organisms, and present-day individuals generally are tiny (for example, today’s Globigerina). However, fossil forams range in size from minute specs to organisms the size of grains of wheat to tests that are the size of a quarter (Nummulites) to individuals that are spindle-shaped and as much as 10 cm long. Depending on the genus, the test of an individual foram may be a single chamber or an intricately coiled series of chambers. Similarly, the wall of the test may be simple in structure, or it may be complexly multilayered.


Overall, foraminiferans are marine organisms. However, they can be extremely environmentally sensitive and are very useful to geologists in endeavors to understand past environments.

Organic Evolution:

For certain portions of the geologic column, foraminiferans are amongst the best index fossils known. An index fossil is one that is useful in determining the age of a given body of rock. An important characteristic of good index fossils is that they are the remains or traces of kinds of organisms that evolved rapidly; hence, a given kind of organism existed on Earth for a short length of time. The result is that a good index fossil can give one precise information as to the age of the rock in which it occurs.



Included here are organisms commonly called radiolarians. Most of these creatures secrete a test composed of silica [= silicon dioxide, the composition of the mineral quartz, the gem-stone opal, and window-glass].



The zoömastigophorans are one-celled heterotrophs that each have at least one flagellum. [The two dots over the second O in the word are called a diaeresis and indicate that the second O is in a separate syllable from the first O.] Included here are both free-living and parasitic organisms.

Included in this phylum is the genus Trypanosoma. Organisms of different species of this genus are responsible for the African sleeping sickness and Chagas’ disease. Trypanosomes are common in the tropical regions of the world. They are passed to humans through the bites of insects, including mosquitoes and sand-flies. For example, the pathogenic protists that cause African sleeping sickness are passed to humans through bites of “tsetse flies”, which suck blood from humans.



The ciliates are so called because they each have a large number of cilia. Individuals of most of the more than 8000 species of ciliates have two types of nuclei, the larger, called macronuclei, and the smaller, called micronuclei.

Examples of members of the phylum:

Balantidium, Didinium, Paramecium, Pharmecium, Spirostomum, Stentor, Tetrahymena, and Vorticella

Individuals of Balantidium coli are commensal organisms in the intestines of swine; they are passed by means of cysts in the faeces. Occasionally they found in humans; in such cases, they are pathogenic, and, in conjunction with bacteria, they erode pits in the intestinal mucosa.

genus Paramecium, and similar forms


Members of the genus Paramecium live in fresh-water. They are free-living organisms.

Osmotic balance is accomplished by contractile vacuoles.


Unlike some protists that reproduce only by fission, members of the genus Paramecium also reproduce by a process called conjugation, in which individuals of two different strains position themselves beside one another and exchange genetic material. Individuals that have participated in conjugation generally undergo frequent mitosis soon thereafter. (Note that asexual reproduction by means of binary fission [a.k.a., transverse fission] is more common than is conjugation.)

genus Vorticella and other ciliates

Members of the genus Vorticella are fresh-water protists that are sessile. [Sessile organisms live attached to other objects; for example, each individual of genus Vorticella is attached to the substrate by a contractile stalk.]



Sporozoans are non-motile parasites. During their life-histories, they form small “spores” that are transmitted from host to host ----- hence, the name of the phylum.

Genus Plasmodium includes the best-known members of the phylum Sporozoa. They cause malaria, which probably has killed more humans than any other disease in history (and continues to do so, by the bye). These parasites are transmitted to humans through the bites of mosquitoes of the genus Anopheles, and they infect and rupture red blood-cells, which causes cycles of fever and chills. (Please, do not confuse the generic name Plasmodium with the technical term “plasmodium” used in studies of “slime-molds” and other organisms.)

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In order to understand this group of organisms, how they function, how they evolved, and so on, you will need to know a number of words, their definitions, and how and when to use the words. Thus, you should put together a list of such words, definitions, and notes. Here are some items to start you in compiling your own list.

Note that many terms in the material in this WEB-page have not been listed separately in this glossary. This does not mean that it would be a wise idea for you to ignore the terms in the material above.

(If a word you seek is not in the following, you might find it in the general glossary.)

cf.  =  compare to [from the Latin "conferre", "to compare"]
q.v.  =  see the entry for the previous word [from the Latin "quod vide", "which see"]


ALGA, (plural, ALGAE; noun)

ALGAE, (plural; singular is ALGA; noun)

This word sometimes is used as though it is the name of a formal taxon, but the term is a "waste-basket term" used to refer all the plant-like protists. [cf.: PROTOZOA]



With respect to reproduction of organisms: (cf., BUDDING).


a member of one of the groups of the Chlorophyta ("green algae") that have "egg-cases", each about the size of the head of a pin and bearing a pattern of spiraling grooves (for example, Chara); one of the "egg-cases" also is called a charophyte.


CILIUM, (plural, CILIA; noun)



FLAGELLUM, (plural, FLAGELLA; noun)

HOLOZOIC, (adj.)


the state in which the male and female gametes are about the same size (compare: oögamy)

LICHEN, (noun)






PROTOZOA, (plural; noun)

This word sometimes is used as though it is the name of a formal taxon, but the term is a "waste-basket term" used to refer all the animal-like protists. [cf.: ALGAE]

[Technically, the singular is PROTOZOÖN, but, casually, is commonly written PROTOZOAN.]


SAND, (noun)

strictly speaking, particles larger than 1/16 mm and smaller than 2 mm in diameter. [Note that this is a technical term in geology. Some people are rather sloppy in their use of this term.]


[literally "layer rock"] a kind of fossil that includes multi-layered mounds, balls, columns or other masses of rock formed by sediment having been trapped on sheet-like colonies of micro-organisms, especially cyanobacterians (= cyanophytes; sometimes called "blue-green algae" in older publications). Comparable organo-sedimentary structures occur in some ecosystems today, for example, Shark Bay, in western Australia.


ZOÖXANTHELLAE, (plural; noun)

dinoflagellate protists that live within the tissues of other organisms, for example, reef-forming corals, in a mutualistic symbiotic relationship. The photosynthesis carried out by the zoöxanthellae provides energy and oxygen to the other organism.

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TBC  =  citation incomplete or otherwise suspect; 
it definitely needs to be checked against the original.
V  =  verified with the original publication
[ ]  =  note / annotation
( )  =  source of information

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Cleveland P., jr., Larry S. Roberts, and Allan Larson, 1995, Integrated Principles of Zoology [ninth edition]: Wm. C. Brown, Dubuque, Iowa. xxi + 983 p. + appendices.

Desowitz, Robert S., 1981, New Guinea Tapeworms & Jewish Grandmothers. Tales of Parasites and People: Avon Books [Hearst Corporation], New York, New York, 224 p. ----- V.

Hegner, Robert, 1938 [1968 reprint], Big Fleas have Little Fleas. or Who's Who Among the Protozoa: Dover Publications, Inc., New York, viii + 285 p. [paper-bound]. ----- V.

Hickman, Cleveland P., jr., Frances M. Hickman, and Lee B. Kats. 2001. Laboratory Studies in Integrated Principles of Zoology [tenth edition]: McGraw-Hill, Boston. xvi + 443 p., specifically, Exercise 6. Protozoan Groups, p. 77-106.

Hickman, Cleveland P., jr., Larry S. Roberts, and Allan Larson. 1997. Integrated Principles of Zoology [tenth edition]: Wm. C. Brown, Dubuque, Iowa. xix + 901 p., specifically, chapter 12 "The Animal-Like Protista", p. 213-238.

Laubenfels, M. W. de., 1955, Receptaculitidae: p. E108-E110 IN Treatise on Invertebrate Paleontology. Part E. Archaeocyatha and Porifera (Raymond C. Moore, ed.): Geological Society of America and University of Kansas Press, New York (now Boulder, Colorado), and Lawrence, Kansas. p. i-xviii + E1-E122.

Lytle, Charles F., 1996, General Zoology. Laboratory Guide [twelfth edition: Wm. C. Brown, Dubuque, Iowa. xvi + 368 p., especially Chapter 5: Protozoa. p. 73-93.

Lytle, Charles F., and John R. Meyer, 2005, General Zoology Laboratory Guide [fourteenth edition]: McGraw-Hill, Boston, xxiii + 372 p. [ISBN 0-07-234900-X; spiral-bound], specifically, Chapter 5. "Animal-like Protista (Protozoa)", p. 71-90.

Margulis, Lynn, and Karlene V. Schwartz, 1998, Five Kingdoms. An Illustrated Guide to the Phyla of Life on Earth: W. H. Freeman and Company, New York. xx + 520 p.

Mason, Kenneth A., Jonathan B. Losos, and Susan R. Singer, “2011”, Biology [“ninth edition”]: McGraw Hill, New York, xxvi + 1279 p., specifically, chapter 29, p. 567-587.

Purves, William K., David Sadava, Gordon H. Orians, and H. Craig Heller,  2001, Life. The science of biology [sixth edition]: Sinauer Associates, Inc./W. H. Freeman and Company., specifically, Ch. 27 Protists and the dawn of the Eukarya, p. 476-499.

Raven, Peter H., George B. Johnson, and Stuart Ira Fox, 1999, Biology [fifth edition]: WCB/McGraw-Hill, Boston, xxviii + 1284 p.

Raven, Peter H., George B. Johnson, Jonathan B. Losos, and Susan R. Singer, "2005" [actually in print in 2004!], Biology [seventh edition]: McGraw-Hill, Boston, xxiii + 1250 p., plus appendices, and so on. [ISBN 0-07-291845-4; hardbound], specifically, chapter 28, "Protists", p. 561-578.

Treatise on Invertebrate Paleontology. Geological Society of America and University of Kansas Press, Boulder, Colorado, and Lawrence, Kansas. [a multi-volume set, with individual volumes published at various dates beginning in 1953].

Vodopich, Darrell S., and Randy Moore, 1999, Biology Laboratory Manual [fifth edition]: WCB/McGraw-Hill, Boston. xi + 546 p., specifically, Exercise 24: Survey of the Kingdom Protista. The Algae, p. 239-250 [24-1 through 24-12[ and Exercise 25: Survey of the Kingdom Protista. Protozoa and Slime-Molds, p. 251-258 [24-1 through 24-8].

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(Editorial note: The word "ankyliography" is analogous to the word "bibliography", but is derived from the Greek word "ankylion", which denotes a link in a chain [as opposed to "biblion", "book"].)

The University of Montreal “Protista Image Data” web-site. (http://megasun.bch.umontreal.ca/protists/protists.html)

The University of California Museum of Paleontology, Berkeley, California, hosts a series of web-pages that deal with protests:

Introduction to the Alveolates” (Foraminifera, Ciliata, Dinoflagellata, and Apicomplexa)

Introduction to the Choanoflagellata

Introduction to the Chromista” (diatoms, kelps, and others)

Introduction to the Basal Eukaryotes

Introduction to the ‘Green Algae’",

Introduction to the Radiolaria

Introduction to the Rhodophyta

Introduction to the "Slime Molds"

Introduction to the Testaceafilosea” (the testate amoebae)

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Davidson, Nick, 2003, NOVA: Deep Sea Invasion: A cinaContract Production for the BBC, WGBH Educational Television, Boston, Massachusetts, video-tape WG36733 [60 minutes; ISBN 1-57807-980-2; MSJ Library 579.8/D311/2001]. ----- V.

[An alga, introduced into the Mediterranean Sea adjacent to Monaco, is spreading ----- to the detriment of the natural communities present.]

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Here is a list of preserved material of the Protista that is available in the Department of Biology.

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A number of the laboratory-manuals listed in the Bibliography contain exercises you might find useful to guide your study, as do other publications not listed.

One of the best ways to stimulate your observational skills is by making drawings of the specimens you examine. Moreover, drawings definitely help jog the memory, once the specimens themselves no longer are available. Hence, you should make drawings of all the specimens you study. These do not need to be equal to the renderings of a professional artist. However, each of your drawings should be well labelled, both as to what is shown and as to the parts and features thereof. There should be a scale on each drawing, of course. Accompanying each drawing should be notes of your observations of colours, changes over the time you observed the specimen, behaviour of the animal (if it was alive), and so on. Again, the goal is to stimulate your observational skills and your memory.

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7 February 2000; 22 and 28 January 2001; 29 January 2002; 22 and 24 January 2005; 12 August 2006; 17 September 2006; 17, 18, 20, and 21 February 2007; 17 September 2009; 04 March 2011; 16 and 19 March 2012