Capsaspora

C. owczarzaki’s life cycle comprises 3 different stages with three different cell types, which was reported only recently.^[when?] Under culture conditions, C. owczarzaki’s filopodial cells crawl attached to the substrate, with active replication until the end of the exponential growth phase. Then, cells start to detach, retracting the branching filopodia and encysting. During this cystic phase, division is stopped. Alternatively, amoebae can actively aggregate to each other by unknown factors, forming a multicellular, aggregative structure and secreting an unstructured extracellular material that seems to prevent direct cell-cell contact.

C. owczarzaki cells, in the filopodial stage, were described as 3 to 5 μm amoebas with a nucleus ⅓ - ½ of the diameter of the cell (containing a central nucleolus), long branched filopodia, mitochondria with flattened cristae, numerous phagosomes, lipid vacuoles, glycogen granules and a Golgi apparatus.^[6][7] Cystic cells measure 4 to 5 μm with a double wall: the outer thin, irregular and loosely attached; and the inner thicker, smooth.^[8]

Taxonomy

C. owczarzaki is together with

Metazoa and Choanoflagellata, which together form the Filozoa^[9][2][10] (See Figure 1). C. owczarzaki was originally described as nucleariids.^[7] However, later molecular ribosomal phylogenies placed C. owczarzaki somewhere closer to animals than the rest of nucleariids.^[11][12][13] Finally, a multi-gene phylogenetic analysis with several opisthokont taxa clearly showed that C. owczarzaki is not a nucleariid, but part of the Holozoa.^[14][15] This was later on corroborated by phylogenomic analyses,^[16][17] one of which ^[17] situated it as sister-group to Ministeria forming the Filasterea clade, which is the sister-group to Choanoflagellatea and Metazoa.^[18][19]