| Colpodella | |
|---|---|
Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Sar |
| Clade: | Alveolata |
| Phylum: | Chromerida |
| Class: | Colpodellophyceae |
| Order: | Colpodellida |
| Family: | Colpodellaceae |
| Genus: | Colpodella Cienkowski, 1865 |
| Species | |
See text | |
| Synonyms | |
| |
Colpodella is agenus ofalveolates comprising fivespecies, and two further possible species:[1] They share all thesynapomorphies ofapicomplexans, but are free-living, rather thanparasitic.[1] Many members of this genus were previously assigned to a different genus -Spiromonas.
Thetype species isColpodella pugnaxCienkowski 1865.
These are small (< 20 μm in diameter) flagellated protists. Thelife cycle of consists of two main stages:flagellatedtrophozoites andcysts, which are the reproductive stage in the life cycle.
Morphologically the trophozoites ofColpodella are similar toPerkinsuszoospores, although the two taxa are not specifically related. The motile stages of both genera have a pair of anterior orthogonalflagella, vesicular mitochondrial cristae, inner alveolar membranes and micropores. BothColpodella andPerkinsus species have open sided truncated conoids (sometimes called pseudoconoids),rhoptries that occupy the length of the cell and smallermicronemes. Both the rhoptries and micronemes arise at the anterior portion of the cell. A three-layered pellicle lies beneath theplasma membrane and is otherwise composed of the alveolar membranes and widely separatedmicrotubules that arise subapically. Some species have extrusive organelles (trichocysts).
UnlikePerkinsus,Colpodella are free-living and are voracious predators of other free-livingprotists. Most species apparently penetrate through the cell membrane and consume the prey's cytoplasm—this mode of feeding is known asmyzocytosis. While feeding the predator attaches its anterior portion—the rostrum—to the prey. The rostrum contains the pseudoconoid, which transforms into a ring ofmicrotubules encircling the attachment zone. The cytoplasm of the prey is then drawn into a large posterior foodvacuole.
Following feeding cells lose their flagella, become spherical, encyst and divide (i.e. reproduce). Thecysts are simple spheres. The food vacuole appears as a large centralvacuole in the cyst; as division progresses the remnant vacuole material is reduced to a residual body. Typically Colpodella divides into four daughter cells (sometimes just two).[1] This is in contrast to true Apicomplexa andPerkinsus, which typically produce many more daughter cells during reproduction—Perkinsus species can produce up to 32 cells, for example, whileToxoplasma produces 128. The daughter cells grow flagella, the cyst wall ruptures, and the cells swim away, leaving the residual body behind. A possible sexual process has been observed in at least two species.[1]
This family appears to be a sister clade to the Apicomplexa.[2] Their life style may be representative of the free living ancestors of the Apicomplexa. One significant difference is that this genus, like thePerkinsea, have an open sided conoid (pseudoconoid) while the Apicomplexa which possess a conoid (theConoidasida) have a closed conoid.
Another genus in this family isAcrocoelus.
Species currently within genus:
Species transferred to other genera:[3]
These organisms are not normally considered to be human pathogens. However, a report of an infection of theerythrocytes in a Chinese woman with a deficiency ofnatural killer cells has been reported.[4]