Orciraptor | |
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Orciraptor agilis attacking an Actinotaenium cell. | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Clade: | Diaphoretickes |
Clade: | SAR |
Phylum: | Cercozoa |
Class: | Sarcomonadea |
Order: | Glissomonadida |
Family: | Viridiraptoridae |
Genus: | Orciraptor |
Species: | O. agilis |
Binomial name | |
Orciraptor agilis Hess & Melkonian, 2013 [1] | |
Orciraptor is a genus of heterotrophic protists, containing the single species Orciraptor agilis. It belongs to the family Viridiraptoridae, in the phylum Cercozoa. [1] [2]
Orciraptor are unicellular organisms with two flagella: a short anterior and a long posterior. The cell nucleus is spherical, surrounded by several Golgi dictyosomes. They have cortical extrusomes homogenously distributed in the cell's periphery. [1]
In particular, Orciraptor agilis are colourless gliding cells that in ventral view are compact in shape, measuring 8–14 μm in length, and in lateral view are oviform or tear-shaped, measuring 12–20 μm in length. The posterior flagellum measures an average of 44 μm, while the anterior measures an average of 15 μm and is usually 33–35 % the length of the posterior flagellum. Their spherical nucleus averages 5 μm in diameter, while the nucleolus averages 3 μm, the mitochondria measure 1.5 × 0.7 μm, and the Golgi bodies appear 1.5–3 in length and 0.5 μm in width. In gliding cells, about six Golgi bodies can be seen surrounding the nucleus in one plane. The cortical extrusomes appear at a density of 25 to 30 granules per 10 μm² of cell surface. Up to about five contractile vacuoles are simultaneously recognisable. The crystals present in the cytoplasm, as is common in the family, are spherical or slightly elongated, measuring 0.7–1 μm, and accumulate in large numbers during starvation, which makes the cells glisten when seen under a differential interference contrast microscope. [1]
Orciraptor are predominantly gliding flagellates, rarely swimming flagellates and surface-attached amoebae. During gliding, their anterior flagellum moves by waving or flapping regularly, which causes a slight rotation or a periodic jiggling of the cell. Cells that are starving glide fast and smoothly. They feed through phagocytosis on a wide range of dead or morbid eukaryotic cells, such as diverse green algae. The behaviors of digestion and reproduction through binary fission in the free-living state are very common, but they are also capable of invading certain algae to digest and reproduce. [1] [2]
In particular, Orciraptor agilis has a gliding velocity averaging 12 μm per second, and a flapping frequency of the anterior flagellum of 1.4–2.3 beats per second at a temperature of 20°C. It is capable of perforating algal cell walls in a circular manner, often leaving behind cell wall lids attached to empty algal cells (see image 1). It leaves elliptical holes on the cell wall (see image 2), measuring 9–11 μm in the largest dimension, seen in Mougeotia prey. It has at least three strategies of feeding: [1]
The name Orciraptor (from Latin orcus ' Orcus ',and raptor 'thief'), meaning 'robber related to the underworld or death', refers to its preference for feeding from the contents of dead cells. The epithet agilis (from Latin agilis 'agile') is due to its remarkably fast and continuous gliding movement of the cells. [1]
Chlamydomonas is a genus of green algae consisting of about 150 species of unicellular flagellates, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae". Chlamydomonas is used as a model organism for molecular biology, especially studies of flagellar motility and chloroplast dynamics, biogenesis, and genetics. One of the many striking features of Chlamydomonas is that it contains ion channels (channelrhodopsins) that are directly activated by light. Some regulatory systems of Chlamydomonas are more complex than their homologs in Gymnosperms, with evolutionarily related regulatory proteins being larger and containing additional domains.
Cercozoa is a phylum of diverse single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, and are instead united by molecular phylogenies of rRNA and actin or polyubiquitin. They were the first major eukaryotic group to be recognized mainly through molecular phylogenies. They are the natural predators of many species of bacteria. They are closely related to the phylum Retaria, comprising amoeboids that usually have complex shells, and together form a supergroup called Rhizaria.
Auranticordis is a genus of rare tetraflagellate eukaryotic organisms within the phylum Cercozoa. Currently there is only one characterized species within this genus: Auranticordis quadriverberis.Auranticordis cells are heart shaped and can range from 35 - 75 µm long and 25 - 70 µm wide. These cells move in a forward gliding motion, and are predators in interstitial marine sand habitats. Auranticordis cells contain several features that are unique and dissimilar from other cercozoans, such as black bodies, reduced acristate mitochondria, putative primary endosymbionts, many orange pigmented extrusomes and the absence of permanently condensed chromosomes.
The sarcomonads or class Sarcomonadea are a group of amoeboid biciliate protists in the phylum Cercozoa. They are characterized by a propensity to move through gliding on their posterior cilium or through filopodia, a lack of scales or external theca, a soft cell surface without obvious cortical filamentous or membranous skeleton, two cilia without scales or hairs, tubular mitochondrial cristae, near-spherical extrusomes, and a microbody attached to the nucleus.
Katabia is a genus of soil-dwelling heterotrophic flagellate cercozoans containing the single species Katabia gromovi, and the only member of family Katabiidae.
Platysulcus tardus is an eukaryotic microorganism that was recently discovered to be the earliest diverging lineage of the Heterokont phylogenetic tree. It is the only member of the family Platysulcidae, order Platysulcida and class Platysulcea.
Rhodelphis is a single-celled archaeplastid that lives in aquatic environments and is the sister group to red algae and possibly Picozoa. While red algae have no flagellated stages and are generally photoautotrophic, Rhodelphis is a flagellated predator containing a non-photosynthetic plastid. This group is important to the understanding of plastid evolution because they provide insight into the morphology and biochemistry of early archaeplastids. Rhodelphis contains a remnant plastid that is not capable of photosynthesis, but may play a role in biochemical pathways in the cell like heme synthesis and iron-sulfur clustering. The plastid does not have a genome, but genes are targeted to it from the nucleus. Rhodelphis is ovoid with a tapered anterior end bearing two perpendicularly-oriented flagella.
Stygiella /ˌstɪ.d͡ʒiˈɛ.lə/ is a genus of free-living marine flagellates belonging to the family Stygiellidae in the jakobids (excavata).
Mesofila is a genus of freshwater heterotrophic protists of the phylum Cercozoa. It is the only genus in the family Mesofilidae. It is a monotypic genus, with the sole species M. limnetica.
Minimassisteria is a marine bacterivorous genus of protists with only one species, M. diva, that presents three different lifestyle forms. It has a widespread geographic distribution. It is an amoeboflagellate most closely related to Massisteria, and together comprise the family Massisteriidae.
The glissomonads are a group of bacterivorous gliding flagellated protists that compose the order Glissomonadida, in the amoeboflagellate phylum Cercozoa. They comprise a vast, largely undescribed diversity of soil and freshwater organisms. They are the sister group to cercomonads; the two orders form a solid clade of gliding soil-dwelling flagellates called Pediglissa.
Pediglissa is a subclass of phagotrophic protists that inhabit soil or freshwater habitats. They were defined in 2018 according to phylogenetic analyses that showed a clade containing the orders Cercomonadida and Glissomonadida. They're the sister group of Paracercomonadida.
Viridiraptoridae, previously known as clade X, is a clade of heterotrophic protists in the phylum Cercozoa. They're a family of glissomonads, a group containing a vast, mostly undescribed diversity of soil and freshwater organisms.
Viridiraptor is a genus of heterotrophic protists, containing the single species Viridiraptor invadens. It belongs to the family Viridiraptoridae, in the phylum Cercozoa.
Aurigamonas is a genus of predatory protists of an unusual cell structure, with two flagella and numerous haptopodia. It is a monotypic genus containing the single species Aurigamonas solis. It is the only genus of the family Aurigamonadidae.
Helkesida is a group of microscopic protists belonging to the supergroup Rhizaria, both discovered through molecular phylogenetic analyses. It contains amoeboid flagellates with two flagella. They are either free-living, mostly on fecal matter, or live inside the gut of animals. Among these amoebae, one lineage has independently evolved aggregative multicellularity similarly to slime moulds.
Bihospites is a genus of symbiontid euglenozoans characterized by the presence of two species of epibiotic bacteria on the cell surface. Bihospites cells are clear, biflagellated, and uninucleated, that range between 40–120 μm long and 15–30 μm wide. Bihospites, as well as other members of the symbiontids, are found in semi-anoxic to anoxic sediments in benthic marine environments. Each cell surface is covered by both rod-shaped and spherical-shaped epibiotic bacteria that may share a commensalistic or mutualistic relationship with Bihospites host cells. Bihospites cells are highly contractile and contain several morphological synapomorphies which are present in euglenozoans, however they also contain several unique morphological traits including a unique C-shaped feeding apparatus.
Heliorapha is a genus of heliozoan protists, amoeboid eukaryotes with stiff axopodia radiating from their cells. It contains one species, Heliorapha azurina. It is classified within a monotypic family Helioraphidae inside the actinophryids, a group of heliozoa that belong to the Ochrophyta along with other protists such as diatoms and brown algae.
Commation eposianum is a species of heterotrophic protists discovered in 1993 in Antarctic waters. It is one of two species in the Commatiida, an order of stramenopiles closely related to actinophryids, a group of heliozoan protists, and to raphidophytes, a group of algae.
Colponemids are free-living alveolates, unicellular flagellates related to dinoflagellates, apicomplexans and ciliates. They are predators of other small eukaryotes, found in freshwater, marine and soil environments. They do not form a solid clade, but a sparse group of deep-branching alveolate lineages.