Taxonomic Overview of Protozoans

1. The Alveolata

Characteristics:

  • Alveoli: Flattened membranous sacs beneath the outer cell membrane.

  • Mitochondrial Cristae: Tubular.

Phylum Ciliophora (Ciliates)

  • Examples: Blepharisma, Didinium, Euplotes, Folliculina, Paramecium, Stentor, Stylonychia, Tetrahymena, Tintinopsis, Tokophyra, Vorticella.

  • Description: Around 3,500 described species. Characterized by cilia used for locomotion and feeding.

Phylum Dinozoa (Dinoflagellates)

  • Examples: Alexandrium (Protogonyaulax), Amphidinium, Ceratium, Dinophysis, Gonyaulax, Gymnodinium, Noctiluca, Perkinsus, Prorocentrum, Pyrocystis, Zooanthella.

  • Description: About 2,000 extant species. Includes photosynthetic and bioluminescent species.

Phylum Apicomplexa

  • Examples: Babesia, Diplospora, Eimeria, Gigaductus, Gregarina, Haplosporidium, Monocystis, Paramyxa, Plasmodium, Sarcocystis, Toxoplasma.

  • Description: About 6,000 species. Predominantly parasitic, mostly invertebrate hosts.

2. The Rhizaria

Characteristics:

  • Defined by molecular characteristics.

  • Includes non-photosynthetic amoebae, amoeboflagellates, and numerous zooflagellates.

  • Mitochondrial Cristae: Tubular.

Phylum Foraminifera

  • Examples: Allogramia, Ammonia, Elphidium, Globigerina, Spirillina.

  • Description: Secrete calcium carbonate tests with pseudopodia protruding through pores. Form Globigerina ooze in marine sediments.

Phylum Radiolaria

  • Characteristics: Possess axopodia (radiating microtubular supports).

Class Polycystinea

  • Examples: Acanthodesmia, Heliodiscus, Hexacontium, Astrosphaera, Spumella, Staurolonche, Triplecta.

  • Description: Marine predators, spherical or nonspherical forms, silica skeleton.

Class Acantharia

  • Examples: Acanthocolla, Acanthometra, Acanthospira, Acanthostaurus, Heliolithium, Stauracon.

  • Description: Marine micropredators with strontium sulfate skeleton.

Phylum Cercozoa

Class Phaeodarea

  • Examples: Aulacantha, Aulosphaera, Castenella, Gymnosphaera, Phaeodina.

  • Description: Microscopic predators with ornate shells of biogenic opal.

3. The Heterokonta

Phylum Stramenopiles

Class Actinophyridae (Heliozoans)

  • Examples: Actinosphaerium, Actinophrys.

  • Description: Polyphyletic; some now classified under Actinophyridae.

Class Opalinata (Opalinids)

  • Examples: Opalina, Proteromonas.

  • Description: Flagellated protozoans, intestinal symbionts of reptiles, fishes, frogs.

4. The Amoebozoa

Characteristics:

  • Branching (ramicristate), tubular mitochondria.

Phylum Amoebozoa

  • Naked Amoebae: Acanthamoeba, Amoeba, Chaos, Entamoeba.

    • Description: Mostly free-living, some pathogenic.

Arcellanids

  • Examples: Arcella, Difflugia, Pentagonia.

  • Description: Shelled amoebae with pseudopodia protruding through a single opening.

Xenophyophoreans

  • Examples: Aschemonella, Homogammina, Psammetta.

  • Description: Large, deep-water amoeboid protozoans with tests made of foreign particles.

Phylum Mastigamoididae

  • Examples: Mastigamoeba, Mastigella.

  • Description: Amoeboid bodies with flagella, found in stagnant water.

Phylum Eumycetozoa

  • Examples: Prostelium, Echinostelium, Dictyostelium.

  • Description: Cellular and acellular slime molds, found in decaying vegetation.

5. The Excavata

Characteristics:

  • Disc-shaped mitochondrial cristae.

  • Deep, ventral feeding groove.

Phylum Parabasala

  • Examples: Dientamoeba, Trichomonas.

  • Description: Flagellates with hydrogenosomes instead of mitochondria.

Class Trichomonadida

  • Examples: Dientamoeba, Trichomonas.

Class Hypermastigia

  • Examples: Holomastigotes, Lophomonas, Trichonympha, Spironympha.

  • Description: Intestinal symbionts of termites, cockroaches, and woodroaches.

Phylum Euglenozoa

Class Euglenida

  • Order Euglenia: Euglena, Peranema, Ploeotia.

  • Description: Mostly photosynthetic, found in freshwater and marine environments.

Order Kinetoplastea

  • Examples: Bodo, Leishmania, Leptomonas, Trypanosoma.

  • Description: Includes free-living, symbiotic, and parasitic species. Kinetoplast present.

6. The Opisthokonta

Characteristics:

  • Posterior flagellum present in some part of the life cycle.

Phylum Choanomonada

  • Examples: Acanthoeca, Codosiga, Diaphanoeca, Monosiga, Proterospongia.

  • Description: Free-living protozoans with a collar of siliceous filaments; may form colonies.

Phylum Fungi

  • Description: Includes true fungi and their protozoan relatives.

Phylum Microsporidia

  • Examples: Buxtehudea, Loma, Metchnikovella, Microfilum, Nosema.

  • Description: Degenerate fungi, intracellular parasites of gregarine protozoans.

Phylum Myxozoa

  • Examples: Chloromyxum, Myxidium.

  • Description: Parasitic, mostly in fishes, related to cnidarians.

7. Additional Groups

Phylum Heterolobsea

  • Examples: Naegleria, Percolomonas, Vahlkampfia.

Diplomonads

  • Examples: Enteromonas, Giardia, Spironucleus, Trigomonas.

  • Description: Flagellates without mitochondria, believed to have lost them secondarily.

Oxymonads

  • Examples: Oxymonas, Polymastimastix, Pyrsonympha.

  • Description: Flagellates with uncertain affiliation.

General References

  • Books and Articles: Include works by Baldauf, Boardman, Bonner, Cavalier-Smith, Cheng, Coombs, Fenchel, Hyman, Keeling, Lee, Matthews, Nikolaev, Parker, Roberts, Sleigh, Zimmer.

  • Web Resources: UCMP, WHO, Malaria Foundation International, FDA.