Protozoa~ Some common freshwater types with links to Micscape resources

Protozoa are a very diverse group of organisms that vary widely in size, shape, features and habit. This page gives an overview of some commonly found freshwater protozoa.

The protozoa have been grouped by their major features. Some of these are artificial groups (i.e. not necessarily related to their taxonomy) but are convenient ones for the pond dipper. More about the classification of algae and protozoa.


Key features 

Micscape links

(those that photosynthesise are often classed as algae)

one or more flagella (whip-like cilia), phytoflagellates are green/ photosynthesise, zooflagellates are not green
<0.4 mm

Flagellated protozoa - includes Euglena, Volvox

Some other common types: Monads e.g. Bodo, Choanoflagellates (flask-shaped with flared collar)


move with pseudopods
0.02 - 5 mm

Amoeba - Protozoa portraits
Amoeba - Video gallery
Amoeba - Smallest page on the web
Amoeba proteus - imaged by different illumination methods

Shelled amoeba

amoeba with a shell e.g. of sand grains
0.1 - 0.4 mm

Protozoan houses - testate amoeba, Arcella, Nebela

Some other common types: Chaos, Pelomyxa

'Sun animalcules'

immobile, spherical with radiating hair-like pseudopods 
0.01 - 1 mm

Smallest page on the web - Heliozoans, Actinosphaerium 

Some other common types: Actinophrys, Acanthocystis

Ciliates - Peritrichs

cylindrical or bell-shaped bodies, undulating membrane of cilia, some stalked, often colonial and attached to animals or plants bell: <0.25mm 

Bell animalcules in 3D - Campanella
Ophrydium - colonial, unstalked
Vorticella - observations on its motile stage

Some other common types: Vorticella, Carchesium

Ciliates - Suctoria 

on water plants and other animals, adult ciliates have lost cilia, sticky tentacles capture prey <0.7 mm

Acineta - Suctoria, ciliates in disguise
Podophyra - an interesting ciliate
Some other common types: Tokophyra, Dendrocometes (lives on gill plates of f/water shrimp)

Other ciliates






various, mostly free living forms

cell usually of a fixed shape but can be contractile, or extending neck, cilia of various forms, fixed mouth
0.01 - 4 mm

Smallest page on the web - ciliates, Euplotes, Stylonichia, etc.
Actinobolina vorax
Coleps - a voracious protozoa
Coleps & Urotricha - predation on rotiferColpidium -
Protozoa portraits
Colpoda - emerging from resting stage
Didinium - a master feeder
Dileptus - a carnivorous protozoa eating Litonotus
Dileptus - notes on it eating Cyclidium
Lacrymaria olor - the 'giraffe' of the protozoan world
Lacrymaria olor - microscopic 'Loch Ness monster'
Litonotus - being eaten by Dileptus
Paramecium - an introduction
Paramecium - Protozoa portraits
Paramecium - by phase contrast
How to study a 'pair of mecia' parts I-III- extensive articles on microscopy techniques to study paramecium's features. Ideal for students.
Stentor - introduction
Stentor - in 3D
Spirostomum- one of the largest ciliates
Spirostomum - observations on its feeding habits

Features of ciliates:
Video gallery - beating cilia
Cilia - an overview



First Page 



Collecting tips 

Insect stages 


Other Micscape resources on protozoa:

Beginners tips on collecting and studying protozoa

A note on demonstrating food vacuoles in ciliates

Vital staining for protozoa and other related mounting techniques (vital staining = while alive)

Natural asphyxia - relaxing protozoa before mounting

Inverted microscopes - homemade viewing troughs for plankton

How fast is an amoeba- a summary of chat prompted by an email

A protozoan undergoes binary fission - with some unusual help!

Some introductory books on freshwater protozoa:

From the Pictured Key Nature series: 'How to know the Protozoa' by Jahn, Bovee and Jahn
Pub. by Wm. C. Brown Company Publishers, Dubuque, Iowa

'A beginner's guide to the collection, isolation, cultivation and identification of freshwater protozoa' by B J Finlay, A Rogerson and A J Cowling. Pub. by Culture Collection of Algae and Protozoa, Freshwater Biological Association, Cumbria, UK, 1988.

'Free living freshwater protozoa: a colour guide' by D.J. Patterson, Pub. by John Wiley & Sons, New York, Toronto. also pub. by Manson Publishing, London. UK. also pub. by U.N.S.W Press, Sydney, Australia

Acknowledgements: This page with links hopefully gives a useful overview, but it's neither a formal identification guide nor comprehensive. Refs. to help identify protozoa are given below.

The artificial groups and key features have been adapted from those in 'Collins field guide to freshwater life' by R Fitter and R Manuel, 1986. Any mistakes are by the web page authors!

Many thanks to all the Micscape contributors whose articles this guide links to. For clarity their names are omitted in the links above. Articles and/or images on any of the groups without links (e.g. protozoa in black type) would be welcomed.

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