| Viridiraptoridae | |
|---|---|
 | |
| Orciraptor agilis attacking anActinotaenium cell. | |
Scientific classification | |
| Domain: | Eukaryota |
| Clade: | Sar |
| Clade: | Rhizaria |
| Phylum: | Cercozoa |
| Class: | Sarcomonadea |
| Order: | Glissomonadida |
| Suborder: | Pansomonadina |
| Family: | Viridiraptoridae Hess & Melkonian, 2013[1] |
| Genera | |
Viridiraptoridae, previously known asclade X, is aclade ofheterotrophicprotists in the phylumCercozoa.[2] They're a family ofglissomonads, a group containing a vast, mostly undescribed diversity ofsoil andfreshwater organisms.[3]
Members of Viridiraptoridae areunicellular biflagellates with naked cells, mostly rigid and variously shaped, without any rostrum or bulge. During the life cycle they can present two different states: a large flagellate state for moving, capable of changing into a surface-attached amoeboid state for feeding. The flagellate state exceeds 10 μm, unlike most knownglissomonad families. The amoeboid state retainsflagella and shows a bridge-like morphology, with several different adhesion sites.[1]
Each cell contains a single vesicularnucleus close to flagellar apparatus, and has an apical position in the flagellate state. Thenucleolus is spherical, roughly central, occasionally showinglacunae. TheGolgi dictyosomes are close to thenuclear envelope. Thecytoplasm is colourless, or opaque due to the presence of globules, granules and crystals inside of it. The feeding stages are seen containing several globules of certainrefractivity. The crystal-like structures are restricted to starving cells and are observed in various shapes:[1]
There are several mitochondria scattered throughout cell, slightly elongate. There are sphericalextrusomes, around 0.5 μm in diameter, directly beneath plasma membrane, but not seen in thepseudopodia. Several contractile vacuoles appear in the periphery, measuring usually less than 2 μm in diameter.[1]
The flagella are naked, heterodynamic (= with different movement each), and arise very close to each other in a slightly acute angle or a right angle. The cellsglide only on their posterior flagellum, which is mostly longer than the anterior flagellum. While gliding, the cell body does not attach to the substrate. The flapping motion of the anterior flagellum often causes motions of the cell body while gliding (such as rotating, jiggling or vibrating). The cells can perform a fluttering swimming locomotion to some extent; this involves both flagella.[1]
Viridiraptoridae areheterotrophic protists that feed byphagocytosis on live and dead eukaryotic cells. They are capable of degrading thecell wall of their prey to feed exclusively on theprotoplast material (as seen in certaingreen algae; see image).[4] They are notbacterivorous. They propagate bybinary fission. Noplasmodia have been observed. They inhabitfreshwater-fed ecosystems.[1]
Twogenera, bothmonotypic (with one species each), comprise the family:[1]