View source for Orciraptor

{{Short description|Genus of predatorial protists}}
{{Italic title}}
{{Speciesbox|taxon=Orciraptor agilis|authority=Hess & Melkonian, 2013<ref name="Orciraptor and Viridiraptor"/>|image=Orciraptor attacking Actinotaenium.webp|image_caption=''Orciraptor agilis'' attacking an ''[[Actinotaenium]]'' cell.}}
'''''Orciraptor''''' is a [[genus (biology)|genus]] of [[heterotrophic]] [[protist]]s, containing the single species '''''Orciraptor agilis'''''. It belongs to the family [[Viridiraptoridae]], in the phylum [[Cercozoa]].<ref name="Orciraptor and Viridiraptor"/><ref name="Enzymatic dissolution feeder"/>
==Morphology==
''Orciraptor'' are [[unicellular]] organisms with two flagella: a short anterior and a long posterior. The [[cell nucleus]] is spherical, surrounded by several [[dictyosome|Golgi dictyosomes]]. They have cortical [[extrusome]]s homogenously distributed in the cell's periphery.<ref name="Orciraptor and Viridiraptor"/>

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 [[Viridiraptoridae|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.<ref name="Orciraptor and Viridiraptor"/>

==Ecology and behavior==
[[File:Perforated Actinotaenium cell with lid.webp|thumb|Image 1. Empty ''[[Actinotaenium]]'' cell excised by ''Orciraptor'', with lid attached.]]
[[File:Perforated dead Actinotaenium cells.webp|thumb|Image 2. ''[[Actinotaenium]]'' cells perforated by ''Orciraptor''.]]
''Orciraptor'' are predominantly [[gliding motility|gliding]] [[flagellate]]s, 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.<ref name="Orciraptor and Viridiraptor"/><ref name="Enzymatic dissolution feeder"/>

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 [[algae|algal]] [[cell wall]]s 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:<ref name="Orciraptor and Viridiraptor"/>
#Extracting cell contents from dead or morbid cells of diverse [[freshwater]] algae, such as [[Zygnematophyceae]] (''[[Mougeotia]]'', ''[[Spirogyra]]'', ''[[Zygnema]]'') and [[Chlorophyceae]] ([[Oedogoniales]], [[Volvocales]]).
#Removing whole cells from gelatinous colonies, such as in [[Volvocales]] and [[Tetrasporales]].
#Invading dead cells of certain size, such as in certain [[Zygnematales]] and [[Oedogoniales]], digesting and propagating in their interior.
==Etymology==
The name ''Orciraptor'' ({{etymology|lat|orcus|[[Orcus]]||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'' ({{etymology|lat|agilis|agile}}) is due to its remarkably fast and continuous gliding movement of the cells.<ref name="Orciraptor and Viridiraptor"/>
==References==
{{Reflist|refs=

<ref name="Orciraptor and Viridiraptor">{{cite journal|vauthors=Hess S, Melkonian M|title=The Mystery of Clade X: Orciraptor gen. nov. and Viridiraptor gen. nov. are Highly Specialised, Algivorous Amoeboflagellates (Glissomonadida, Cercozoa)|journal=Protist|volume=164|issue=5|date=2013|pages=706–747|issn=1434-4610|doi=10.1016/j.protis.2013.07.003}}</ref>

<ref name="Enzymatic dissolution feeder">{{cite journal|vauthors=Moye J, Schenk T, Hess S|title=Experimental evidence for enzymatic cell wall dissolution in a microbial protoplast feeder (Orciraptor agilis, Viridiraptoridae)|journal=BMC Biol|volume=20|pages=267|date=2022|issue=1 |doi=10.1186/s12915-022-01478-x|pmid=36464670 |pmc=9721047 |doi-access=free }}</ref>

}}
{{Taxonbar|from1=Q113352166}}

[[Category:Rhizaria genera]]
[[Category:Taxa described in 2013]]