Domain Eukaryota Phylum Apusozoa | Class Hilomonadea Rank Order | |
Similar Varisulca, Aphelida, Holomycota, Corallochytrium, Discosea | ||
Rigifilida is a group of non-ciliate phagotrophic protozoa. It consists on two families: Micronucleariidae and Rigifilidae.
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Characteristics
Cells of rigifilids are covered with either a single or a double-layered submembrane pellicular lamina that makes them rigid in consistence. Slender branching filopodia emanate from a ventral aperture of the cell and are employed to collect bacteria upon which they feed and to attach the organism to the substratum. Around this aperture, the pellicle is reflexed around forming a peristomial collar. Other notable features are flat and irregular shaped mitocondrial cristae, a single dorsal nucleus and the lack of centrioles and cilia.
Phylogenetic Affinities and Classification
Although Rigifilida is currently classified within the class Hilomonadea in the phylum Apusozoa, both of those higher taxa have not been recovered as monophyletic, natural groups in molecular phylogenetic analyses. Apusozoa is a polyphyletic grouping whose members are scattered through the base of the Unikonta. The position of Rigifilida may even lie outside of Unikonta, as in the only molecular analysis it has been included so far, it clusters with Collodictyonidae/Diphylleidae with a very weak branch support.