This description of the diversity of protists is based on two reviews (Patterson, 1994, 1999) . These papers present one of several differing views about the diversity and inter-relationships of the protists and other eukaryotes (e.g. Cavalier-Smith, 1993, 1994; 1998; Corliss, 1984, 1994; Margulis et al., 1990). Patterson argues that the groups which share a common cytological organization (an 'ultrastructural identity' - Patterson and Brugerolle, 1988) generally constitute monophyletic lineages. The concept of ultrastructural identities is used to generate the concept that there are about60 types of eukaryotes.
An ultrastructural identity refers to the appearance of a variety of features. They include:
- the shape of the cristae in the mitochondria (cristae may be tubular - long or bleb shaped or branching; or they may be discoidal with or without a pedicel, or they may be flat plates); the form of cristae varies within a species or group of protists on rare occasions
- the presence or absence of hairs, scales or other excrescences on the flagella
- the component parts of the transition region where the 9+2 organization of the axoneme transforms into the nine triplet structure of the basal bodies
- the length and orientation of the basal bodies and their associations with other organelles
- the nature of the microtubular and other rootlet structures which arise from the basal bodies, and the associations between these and other organelles
- the source and deployment of other microtubular or other cytoskeletal arrays within the cell, or under the cell surface
- the nature, composition, origins and appearance of any extracellular materials
- presence and nature of microtubule organizing centres
- number, nature and heterogeneity of nuclei, intra-envelope, intranuclear and paranuclear inclusions
- the behaviour of the nuclear envelope during mitosis (is it retained, is it completely lost, or is it perforated in regions by the intruding spindle), and where does the spindle nucleate, is it located within the nucleus, or external to the nucleus, or does it start in the cytoplasm and penetrate into the nucleus)
- if there is a chloroplast, how many bounding membranes, how many thylakoids per lamella, contained (e.g. stigma) or associated (e.g. nucleomorph) organelles
- identity and nature of other endomembranous organelles in the cell
- other idiosyncracies
This approach identifies the types of eukaryotes listed below. As new taxa are identified by further exploration of the world around us or by the study of genera with ambiguous identities (see second table below) so new ultrastructural identities are revealed, and this list lengthens. As relationships are agreed through comparative molecular biology or comparative morphology, so the list shortens. Over the last decade the list has shortened from about 85 lineages to about 60 lineages.
Lineages of eukaryotes: groupings which share an ultrastructural identity and have no evident sister group
| Acantharea | a type of radiolaria |
|---|---|
| Alveolates | dinoflagellates, ciliates, and apicomplexan sporozoa |
| Ancyromonas | genus of heterotrophic flagellates |
| Apusomonads | several genera of heterotrophic flagellates |
| Biomyxa | genus of free-living amoebae |
| Centroheliozoa | several genera of heliozoa |
| Cercomonads | several genera of heterotrophic flagellates |
| Chlorarachniophytes | amoeboid organisms with symbiotic algal plastids |
| Coelosporidium | parasitic flagellates |
| Collodictyon | genus of heterotrophic flagellates |
| Copromyxids | slime-mould like protists |
| Cryothecomonas | genus of heterotrophic flagellates |
| Cryptomonads | several genera of algal and heterotrophic flagellates |
| Desmothoracids | several genera of heliozoon-like protists |
| Dimorphids | several genera of heliozoon-like flagellates |
| Diphylleia | genus of heterotrophic flagellates |
| Discocelis | genus of heterotrophic flagellates |
| Ebriids | several genera of heterotrophic flagellates |
| Ellobiopsids | several genera of parasitic flagellates |
| Entamoebidae | several genera of amitochondriate and parasitic amoebae |
| Excavates | flagellates, diplomonads, jakobids, retortamonads, Trimastix, Carpediemonas, heterolobosea, etc. |
| Euglenozoa | flagellates, euglenids and kinetoplastids |
| Fonticula | a genus of slime-mould-like protists |
| Glaucophytes | protists with photosynthetic endosymbionts |
| Granuloreticulosa | amoebae, mostly foraminifera |
| Gymnophrea | several genera of amoebae |
| Gymnosphaerida | a type of heliozoon |
| Haplosporids | parasitic sporozoa |
| Haptophytes | algal flagellates (also called prymnesiophytes) |
| Kathablepharids | several genera of heterotrophic flagellates |
| Komokiacea | large marine amoebae |
| Luffisphaera | marine protists |
| Ministeria | genus of heterotrophic flagellates |
| Multicilia | genus of heterotrophic flagellates |
| Nephridiophagids | parasitic protists |
| Nucleariidae | amoebae with thin pseudopodia |
| Opisthokonts | chytrids, fungi, microsporidia, collar-flagellates, metazoa |
| Oxymonads | several genera of heterotrophic flagellates |
| Parabasalids | several genera of parasitic heterotrophic flagellate |
| Paramyxea | parasitic sporozoa |
| Pelobionts | several genera of amitochondriate flagellates |
| Phaeodarea | a type of radiolaria |
| Phagodinium | parasitic flagellates |
| Phalansterium | genus of heterotrophic flagellates |
| Plasmodiophorids | parasitic flagellates |
| Polycystinea | a type of radiolaria |
| Pseudospora | parasitic amoebo-flagellates |
| Ramicristates | most amoebae, including dictyostelid and myxomycete slime moulds and Hyperamoeba |
| Red algae | unicellular and multicellular algae |
| Rosette agent | parasitic protist |
| Spironemids | several genera of heterotrophic flagellates |
| Spongomonads | several genera of heterotrophic flagellates |
| Stephanopogon | genus of heterotrophic flagellates |
| Sticholonche | genus of heliozoa with mobile arms |
| Stramenopiles | major group, includes diatoms, chrysophytes, brown algae, opalines, and (incertae sedis) the hamatores which include Caecitellus and the pseudodendromonads |
| Telonema | genus of heterotrophic flagellates |
| Thaumatomonads | several genera of heterotrophic flagellates |
| Vampyrellids | fungus- and alga-eating amoebae |
| Viridaeplantae | green algae and the green plants |
| Xenophyophores | large marine amoebae |
Genera of protists for which no clear identity has been developed (after Patterson, 1999)
| Free-Living Heterotrophic Flagellates | Parasitic Protists | Algal Protists | Amoeboid Protists | Nature Uncertain |
|---|---|---|---|---|
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