Cell structure Rigifila are
unicellular protozoa. As all members of
Rigifilida, they lack
cilia, but generate slender branching
filopodia that can attach to the substrate. These filopodia lack any
microtubules or
extrusomes, and arise from the ventral side of the cell through a common filopodial stem, which is surrounded by an aperture. Under the cell membrane, they present a double-layered
proteinaceous lamina (or pellicle) that covers the whole cell body, making it rigid except for the ventral aperture. They have one
nucleus on the dorsal side of the cell.
Rigifila, and by extension all of Rigifilidae, differs from
Micronucleariidae by having two pellicular dense layers, as opposed to a single-layered pellicle. In addition, they exhibit several broad microtubular bands, of around 20 microtubules each, underneath the dorsal and lateral pellicle, while
Micronuclearia lost all cytoplasmic microtubules.
Mitochondrial cristae are completely flat in
Micronuclearia, but partially flat and partially inflated in
Rigifila.
Feeding Rigifila are free-living
phagotrophic organisms. They feed on
bacteria, which they collect with their
filopodia and ingest at the base of a ventral collar or aperture that surrounds the base of the filopodial stem. == References ==