world of amoeboid organisms


Cercozoa Cavalier-Smith 1998, emend. Adl et al. 2005; emend. Cavalier-Smith 2018

Diagnosis: Diverse clade lacking distinctive morphological or behavioural characters; biciliated and/or amoeboid, usually with filopodia; most with tubular mitochondrial cristae; cysts common; kinetosomes connecting to nucleus with cytoskeleton; usually with microbodies and extrusomes.

Imbricatea Cavalier-Smith 2011
Test proteinaceous, with calcified inner layer, or completely chitinoid with recycled mineral particles; pseudopodia conical, pointed, clearly ectoplasmatic, sometimes branched and may anastomose; Cryptodifflugia stands out by having orthomitosis, but it is unclear if this feature is characteristic for the group.

Thecofilosea Cavalier-Smith 2003, emend. Cavalier-Smith 2011
With robust organic extracellular theca, unlike most other Cercozoa, which are usually naked or with scales; ventral filose pseudopodia emerge from ventral groove; two cilia with divergent kinetosomes, secondarily lost in Rhizaspidae and the euglyphid amoebae, and restricted to zoospores in phaeodarians; ancestrally benthic gliding on posterior cilium only, but some secondarily planktonic swimmers amongst which ebriids have lost pseudopodia; theca with perforations for cilia and for pseudopodia, and three perforations in phaeodaria (thus also called Tripylea Hertwig 1879), which have surrounded it by a pseudopodial net containing a pigmented phaeodium, thus converting it into a ‘central capsule’, but not homologous with that of Polycystinea of Radiolaria; silica scales absent, unlike many Imbricatea, but hollow silica endoskeleton in all ebriids and most phaeodarians.

Granofilosea Cavalier-Smith & Bass 2009
With very fine branching or unbranched granuloreticulopodia bearing obvious extrusomes as the granules at frequent rather regular intervals, or with radiating, sometimes branched, axopodia with similar granules; pseudopodia supported by internal microtubules and typically appressed to the substratum during feeding, in a semi-immobile state; in most species, pseudopodia do not anastomose; some with biciliated swimming or gliding stage.

Incertae sedis: Chlamydophryidae de Saedeleer 1934: Capsellina, Chlamydophrys, Clypeolina, Diaphoropodon, Lecythium, Leptochlamydophrys, Penardeugenia.

Note: this is not a complete overview of Cercozoa.

After Adl et al, Revised Classification of Protozoa, 2012

Cercozoa is a diverse, increasingly well characterized phylum of protists founded mainly on the basis of 18S rDNA phylogenies that revealed a phylogenetic relationship between a variety of gliding zooflagellates and filose amoebae and the plasmodiophorid plant parasites. This diversity of cercozoan body forms includes:

• filose testate amoebae
• amoeboflagellate algae
• zooflagellates with pseudopodia and siliceous scales
• diverse parasites
• naked reticulose amoebae
• testate reticulose amoebae
• colonial flagellates
• planktonic swimming flagellates
• numerous small gliding flagellates
• helioflagellates
• soft-bodied amoeboflagellates
• thecate or scaly amoeboflagellates with a marked groove or cleft
• and even protists with axopodia

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