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Protozoa -- "Unicellular Eukaryotes"


From The
Zoological Record

The core information for this page is taken from the website of The Zoological Record. The original text has been abbreviated, some taxonomic groups are added, and links to further information have been expanded. For convenience the taxonomic list is distributed among several separate pages.

Protozoa -- 'unicellular' eukaryotes, may be referred to as protists, protozoans, unicellulates etc; often now included in a separate kingdom together with fungal protists and algae -- as the Protista or Protoctista -- a grouping of problematical and multiple lineage; many groups have representatives traditionally studied by both algologists and zoologists, leading to much confusion in terminology and classification; the scheme followed here takes a zoological viewpoint --[links images]


Mastigophora mastigophorans, flagellates.

    Phytomastigophorea phytoflagellates, which have chloroplasts and are photosynthetic.

      Chloromonadida chloromonads, chlorophytes (Heterosigma).

      Chrysomonadida chrysomonads, chrysophytes, yellow-green algae (Mallomonas, Ochromonas).

      Cryptomonadida cryptomonads, cryptophytes, found all over the world -- both free living in moist places and parasitic in animals (Cryptomonas, Rhodomonas)

      Dinoflagellida dinocysts, dinoflagellates, dinomastigotes, dinophytes, mostly marine planktonic but some freshwater representatives, may form 'red tides' (Gonyaulax), be luminescent (Noctiluca), form symbiotic relationships with coelenterates (Gymnodinium), and others (Peridinium)

      Euglenida euglenoid flagellates, euglenophyta, mostly inhabit freshwater enriched with organic matter (Euglena), some marine or brackish, a few are parasitic in animals.

      Prymnesiida prymnesiophytes, haptophytes, golden motile algae viewed by marine biologists as calcareous nannoplankton plankton and by palaeontologists as coccolithophorids (Coccolithus, Prymnesium)

      Silicoflagellida silicoflagellates (Dictyocha)

      Volvocida (Chlamydomonas, Chloromonas, Dunaliella, Volvox)

    Zoomastigophorea zooflagellates

      Choanoflagellida choanoflagellates, collar-flagellates, may be solitary (Salpingoeca) or colonial (Proterospongia), colonial choanoflagellates resemble sponges and it is thought that they might represent what an ancestor of all metazoans might have been like --[ucmp]

      Diplomonadida some freeliving in freshwater but most commensal or parasitic in intestines of animals (Giardia, Hexamita)


      Kinetoplastida include the freeliving bodonids and parasitic trypanosomes (Leishmania, Trypanosoma)


      Proteromonadida (Proteromonas)

      Trichomonadida (Trichomonas, Tritrichomonas)

Opalinata (Opalina)

Sarcodina made up of superclasses Rhizopoda (amastigote amoebae and thecamoebae) and the Actinopoda which includes the radiolarian groups


    Gymnamoebia (Gymnamoeba)

      Amoebida (Acanthamoeba, Amoeba, Entamoeba)

      Pelobiontida karyoblasteans,freeliving amoeboid protists completely lacking mitochondria (Pelomyxa)

      Schizopyrenida sometimes called amoeboflagellates, common in soils, some are pathogenic in man(Naegleria)


      Arcellinida (Arcella, Difflugia)



    Acarpomyxea (Leptomyxa)

    Acrasea cellular slime moulds (Acrasis)

    Eumycetozoea includes cellular slime moulds, the prosteliids (Ceratiomyxa) and dictyosteliids (Dictyostelium, Polysphondylium), together with acellular, plasmodial or true slime moulds -- myxogastrids, myxomycota, myxomycetes (Physarum)

    Plasmodiophorea mostly obligate parasites of plants (Plasmodiophora, Spongospora)

    Filosea includes aconchulinids and gromiids (Euglypha)

    Granuloreticulosia includes Foraminifera (Ammonia, Anomalina, Globigerina, Globorotalia, Trochammina)

    Xenophyophorea (Psammina)

    Acantharea radiolarian group

    Polycystinea radiolarian group

    Phaeodarea radiolarian group

    Heliozoea primarily freshwater (Acanthocystis, Dimorpha, Raphidocystis)

Labyrinthomorpha labyrinthulids, slime nets, form transparent colonies of individual cells (Labyrinthula)

Apicomplexa named for 'apical complex' a distinctive arrangement of organelles at one end of the cell, all are spore forming parasites of animals and include the haematozoan parasites of vertebrate blood --[ucmp ToL]

    Perkinsea (Perkinsus)


    Gregarinia gregarines (Gregarina, Nematopsis)

    Coccidia coccidians, malarial parasites (Cryptosporidium, Eimeria, Hepatozoon, Isospora, Plasmodium, Toxoplasma)

    Piroplasmia piroplasmids (Babesia, Theileria)

Microspora mostly intracellular parasites of vertebrates (Glugea, Microsporidium, Nosema)

Ascetospora (=Haplospora) includes the spore forming parasites Haplosporidia (Haplosporidium, Urosporidium) and Paramyxea

Myxozoa (=Cnidospora) traditionally considered protistan parasites but recent molecular evidence supports an origin with parasitic cnidarians [ToL]

    Myxosporea myxosporidians, parasites of vertebrates and often disease causing in fish (Ceratomyxa, Henneguya, Kudea, Myxidium, Myxobolus)

    Actinosporea actinomyxids, parasites of invertebrates

Ciliophora ciliates, infusorians, characterized by having cilia [ucmp]


    Gymnostomatia includes Katyorelictida (Loxodes) and Prostomatida (Didinium)

    Vestibulifera includes Colpodida (Colpoda), Entodiniomorpha (Entodinium, Polyplastron) and Trichostomatida (Balantidium, Dasytricha)

    Hypostomatia includes Apostomatida, Cyrtophorida and Nassulida

    Suctoria (Trichophrya)


    Hymenostomatida includes Astomatida, Hymenostomatida (Colpidium, Paramecium, Tetrahymena) and Scuticociliatida (Uronema)


    Peritrichia peritrichs (Ophrydium, Trichodina, Vorticella)


    Spirotrichia includes Heterotrichida (Bursaria, Metopus, Stentor), Hypotrichida (Euplotes, Oxytricha), Oligotrichida (Strombidium, tintinnids)


Protozoa  |  Metazoa  |  Invertebrates  |  Arthropods  |  Hemichordates  |  Chordates  |  Craniates
Vertebrates  |  Unicellular-organisms  |  Sponges  |  Corals  |  Echinoderms  |  Worms  |  Mollusks
Crustaceans  |  Arachnids  |  Insects  |  Fish  |  Amphibians  |  Reptiles  |  Birds  |  Mammals

Back to: Evolution   |   Zoology

Send suggestions, additions, corrections to Richard White at R. White

protozoa.htm 3/8/2001     Links verified 3/8/2001