Viridiraptoridae | |
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Orciraptor agilis attacking an Actinotaenium cell. | |
Scientific classification | |
Domain: | Eukaryota |
Clade: | Diaphoretickes |
Clade: | SAR |
Phylum: | Cercozoa |
Class: | Sarcomonadea |
Order: | Glissomonadida |
Suborder: | Pansomonadina |
Family: | Viridiraptoridae Hess & Melkonian, 2013 [1] |
Genera | |
Viridiraptoridae, previously known as clade X, is a clade of heterotrophic protists in the phylum Cercozoa. [2] They're a family of glissomonads, a group containing a vast, mostly undescribed diversity of soil and freshwater organisms. [3]
Members of Viridiraptoridae are unicellular 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 known glissomonad families. The amoeboid state retains flagella and shows a bridge-like morphology, with several different adhesion sites. [1]
Each cell contains a single vesicular nucleus close to flagellar apparatus, and has an apical position in the flagellate state. The nucleolus is spherical, roughly central, occasionally showing lacunae. The Golgi dictyosomes are close to the nuclear envelope. The cytoplasm 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 certain refractivity. 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 spherical extrusomes, around 0.5 μm in diameter, directly beneath plasma membrane, but not seen in the pseudopodia. 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 cells glide 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 are heterotrophic protists that feed by phagocytosis on live and dead eukaryotic cells. They are capable of degrading the cell wall of their prey to feed exclusively on the protoplast material (as seen in certain green algae; see image). [4] They are not bacterivorous. They propagate by binary fission. No plasmodia have been observed. They inhabit freshwater-fed ecosystems. [1]
Two genera, both monotypic (with one species each), comprise the family: [1]
A flagellate is a cell or organism with one or more whip-like appendages called flagella. The word flagellate also describes a particular construction characteristic of many prokaryotes and eukaryotes and their means of motion. The term presently does not imply any specific relationship or classification of the organisms that possess flagella. However, the term "flagellate" is included in other terms which are more formally characterized.
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.
Cercomonads are small amoeboflagellates, widespread in aqueous habitats and common in soils.
Monadofilosa is a grouping of Cercozoa. These organisms are single-celled amoeboid protists.
Thecofilosea is a class of unicellular testate amoebae belonging to the phylum Cercozoa. They are amoeboflagellates, organisms with flagella and pseudopodia, distinguished from other cercozoa by their scale-lacking test composed of organic material. They are closely related to the Imbricatea, a group of testate amoebae with tests composed of inorganic silica scales.
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.
Thaumatomastix is a protist genus of the order Thaumatomonadida, within the phylum Cercozoa and the class Imbricatea. Its species are aquatic, feeding on algae and appearing in waters of a wide range of temperatures and salinities, and are 15-50 micrometers long. They can interchange between flagellated and amoeboid forms, and are notable for being covered in both spiny and flattened siliceous scales.
Katabia is a genus of soil-dwelling heterotrophic flagellate cercozoans containing the single species Katabia gromovi, and the only member of family Katabiidae.
The vampyrellids, colloquially known as vampire amoebae, are a group of free-living predatory amoebae classified as part of the lineage Endomyxa. They are distinguished from other groups of amoebae by their irregular cell shape with propensity to fuse and split like plasmodial organisms, and their life cycle with a digestive cyst stage that digests the gathered food. They appear worldwide in marine, brackish, freshwater and soil habitats. They are important predators of an enormous variety of microscopic organisms, from algae to fungi and animals. They are also known as aconchulinid amoebae.
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.
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.
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.
Orciraptor is a genus of heterotrophic protists, containing the single species Orciraptor agilis. It belongs to the family Viridiraptoridae, in the phylum Cercozoa.
Viridiraptor is a genus of heterotrophic protists, containing the single species Viridiraptor invadens. It belongs to the family Viridiraptoridae, in the phylum Cercozoa.
The pansomonads, suborder Pansomonadina, are a group of heterotrophic protists that belong to the phylum Cercozoa. Some of them are helioflagellates, with characteristics of heliozoans and amoebo-flagellates.
Saccharomycomorpha is a genus of non-flagellated protists with a rare yeast-like appearance, containing the single species Saccharomycomorpha psychra. It is the only genus of the family Saccharomycomorphidae, within the cercozoan order Glissomonadida. Before its description in 2021 it was known as clade T, recovered from environmental DNA in previous phylogenetic analyses.
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.
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.
An amoeboflagellate is any eukaryotic organism capable of behaving as an amoeba and as a flagellate at some point during their life cycle. Amoeboflagellates present both pseudopodia and at least one flagellum, often simultaneously.