Full Answer
Are Cercozoans unicellular?
The Cercozoa are a group of single-celled eukaryotes.
Are Cercozoans protozoans?
The protozoan phylum Cercozoa embraces numerous ancestrally biciliate zooflagellates, euglyphid and other filose testate amoebae, chlorarachnean algae, phytomyxean plant parasites (e.g. Plasmodiophora, Phagomyxa), the animal-parasitic Ascetosporea, and Gromia.
Are Cercozoans heterotrophic?
In a recent study conducted in the coastal dunes of the Baltic Sea, using a primer-independent method, Khanipour Roshan et al. [20] showed that Cercozoa were one of the dominant heterotrophic protist groups in young algal and cyanobacterial biocrusts.
What organisms are included in the Amoebozoans?
Amoebozoa includes many of the best-known amoeboid organisms, such as Chaos, Entamoeba, Pelomyxa and the genus Amoeba itself. Species of Amoebozoa may be either shelled (testate) or naked, and cells may possess flagella. Free-living species are common in both salt and freshwater as well as soil, moss and leaf litter.
What protist has two flagella?
DinoflagellatesDinoflagellates possess two flagella, one (the transverse flagellum) may be contained in a groove-like structure around the equator of the organism (the cingulum), providing forward motion and spin to the dinoflagellate, the other (the longitudinal flagellum) trailing behind providing little propulsive force, mainly ...
What is the primary method of locomotion for the phylum Cercozoa?
Amoeboid Protists They move primarily using pseudopodia with shapes that vary in different taxa from finely pointed and branching filose extensions to blunt lobopodia. The pseudopodia are used both for movement and for engulfing food particles.
Do Rhizaria have mitochondria?
Nearly all rhizaria have mitochondria with tubular cristae. Rhizaria descend from a heterotrophic eukaryote ancestor with two flagella.
What are Radiolarians made of?
silicaThe Radiolaria, also called Radiozoa, are protozoa of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ectoplasm. The elaborate mineral skeleton is usually made of silica.
Which of the following are characteristics of red algae?
General Characteristics of Red AlgaeLack of flagella and centrioles.Presence of photosynthetic pigments.Found both in marine and freshwater.They show biphasic or triphasic life cycle patterns.They are a multicellular, filament, blade structure.Stored food is in the form of starch and polymers of galactan sulphate.More items...•
How do Amoebozoans move?
Amoebozoan cells characteristically exhibit pseudopodia that extend like tubes or flat lobes. These pseudopods project outward from anywhere on the cell surface and can anchor to a substrate. The protist then transports its cytoplasm into the pseudopod, thereby moving the entire cell.
Where are Amoebozoans found?
Amoebozoans live in marine environments, fresh water, or in soil. In addition to the defining pseudopodia, they also lack a shell and do not have a fixed body.
Do Amoebozoans have cilia?
Phylogenetic Relationships and Specializations. Amoebozoa can be further divided into the phyla Conosa, which either have cilia or a flagellum or have secondarily lost them; Lobosa, which never have cilia or flagella; and the free-living, anaerobic, flagellated Breviatea (Fig.
Are protozoans heterotrophic?
5.2. Protozoa are unicellular, eukaryotic organisms that can be several mm in length, although most are much smaller. Most protozoa are heterotrophic and survive by consuming bacteria, yeast, fungi, and algae.
Are helminths heterotrophic or autotrophic?
Fungi, Protozoa, & Helminths (all eukaryotes, heterotrophic)
Are protozoans heterotrophic or autotrophic?
heterotrophicThe protozoans are unified by their heterotrophic mode of nutrition, meaning that these organisms acquire carbon in reduced form from their surrounding environment.
Are algae heterotrophic?
In other words, most algae are autotrophs or more specifically, photoautotrophs (reflecting their use of light energy to generate nutrients). However, there exist certain algal species that need to obtain their nutrition solely from outside sources; that is, they are heterotrophic.
How do radiolarians glow?
Of the 400–800 radiolarian and 400–500 phaeodarian living species, only around a dozen are known to be bioluminescent. Both radiolarian and phaeodarian bioluminescence is triggered by mechanical stimulation. Investigated radiolarians respond with a glow lasting typically 1–2 s, but glows lasting >3 s have also been detected, such as in the colonial Rhaphidozoum acuferum and in the solitary Thalassicolla nucleata. The light is blue with a relatively short peak wavelength of 440–460 nm, as compared to other bioluminescent members of the marine plankton, such as dinoflagellates, ctenophores, and crustaceans with wavelength maxima of 470–490 nm.
How to detect microbes in water?
Several methods have been used to detect microbes in drinking water, often aided by the amplification of specific genetic markers via polymerase chain reaction (PCR). Such methods have detected bacteria closely related to public health-relevant genera such as Legionella and Mycobacterium in drinking water ( Figure 2 ). While species of the latter genera have been associated with waterborne illness, their detection does not necessarily imply a health risk or a deficiency in water treatment, as most species within these genera are not pathogenic to humans. Nucleic acid-based methods have also detected fastidious organisms in drinking water such as nitrifying bacteria, whose presence may degrade drinking water quality and thus may reflect inadequate water treatment practices.
Where are radiolarians found?
Radiolarians and phaeodarians are unicellular zooplankton found in all oceans, with the exception of brackish areas. In older taxonomy phaeodaria were grouped with the radiolarians, but they are now within the phylum Cercozoa, while the radiolarians belong to the Retaria, both in the super-phylum Rhizaria. Recent changes in taxonomy affect descriptions of the distribution of bioluminescence in older literature, where no phaeodarian species where considered bioluminescent. Phaeodarians are solitary, while radiolarians live solitary or in colonies. Cells from both groups range in size from 30 µm to 2 mm, and radiolarian colonies can reach three meters in length. Radiolarian and phaeodarian cells are organized in a central and an outer capsule, separated by a membrane. Some radiolarians harbor symbiotic microalgae, e.g., dinoflagellates, in the outer capsule, and their most striking morphological characteristic are the species-specific skeletons of opal-silica or strontium-sulfate (Fig. 2 (A) ).
Why is global distribution important for protists?
Global distribution has been used as an argument for low protist diversity as it should prevent speciation by geographic isolation or allopatry, the speciation mechanism considered most important. However, most groups detected in environmental surveys show a large 18S rDNA sequence variability, thus strongly disagreeing with the view of low protist diversity. The significance of this large intragroup rDNA diversity is presently not understood but can be relevant, since differences as small as 1% in the 18S rDNA might imply millions of years of evolutionary distance. It is also not clear how this large phylogenetic diversity of protists translates into functional diversity in the open sea or how this diversity is generated and maintained. One possibility is to view the seemingly homogeneous pelagic habitat as a continuum of environmental niches. Thus, there is a large genetic diversity of marine protists, which may have a global distribution, but the ecological implications of this large diversity remain to be investigated.
Which supergroup contains parasites?
More contentious are the last two supergroups, the excavates and the chromalveolates, both of which contain important parasitic lineages. The chromalveolates include three major protistan groups which all contain members with chloroplasts derived from a red algal endosymbiosis [53]. The first major group, the alveolates, has long been recognised on morphological grounds [54]; it harbours parasites such as Plasmodium, Toxoplasma and Cryptosporidium. These apicomplexans are reliably placed as related to the dinoflagellates (another group with parasitic representatives) and the ciliates [55,56]. In turn, the alveolates are thought to be related to the stramenopiles, another group initially recognised on morphological grounds [57] that includes diatoms, brown algae and the oomycetes. The third major group in the chromalveolates includes the haptophytes, kathablepharids and cryptophytes [51,58]. The support joining alveolates, stramenopiles and the cryptophyte–haptophyte lineage is variable [59]. Recent analyses have placed the Rhizaria as robustly sister to the group of chromists and alveolates ( Fig. 1 C) which even raises the question of whether there should be six supergroups or five [45,51,60].
What is the radiolarian bioluminescence reaction?
The radiolarian bioluminescence reaction involves the luciferin coelenterazine in combination with a Ca 2+ -dependent photoprotein or luciferase. Coelenterazine is the most widespread luciferin, also utilized by some crustaceans, coelenterates, squid, brittlestars, and fish. Small crustaceans (copepods) are one original producer of coelenterazine, which is then distributed throughout the food web and obtained by other organisms that have a dietary requirement for the substance. Whether radiolarians are producers or consumers of coelenterazine is not known, but they are unlikely to obtain the substance from copepod prey as these feed on bacteria and other microorganisms.
What are the closest relatives of Cercozoa?
The closest relatives of Cercozoa are the Retaria (Foraminifera and Radiozoa; Cavalier-Smith 1999). Radiozoa are all marine unicellular organisms with microtubule-supported axopodia; they comprise the classical polycystine Radiolaria (with silica skeletons), the Acantharea (with strontium sulphate skeletons), which both also possess axopodia, and the curious floating and axopodially swimming Sticholonche which is not mineralized. Radiozoa now excludes the Phaeodarea, which despite their silica skeleton and axopodia, clearly belong in Cercozoa. Phaeodarea appear to be related to the filosan group known as Thecofilosea, which includes filose testate amoebae without silica scales and also the exclusively marine ebriid flagellates, which like the Phaeodarea have a hollow silica endoskeleton, which might therefore have been a common ancestral character for both groups. A hollow silica endoskeleton is unknown in any other eukaryotes. Two groups of Cercozoa (the euglyphid testate amoebae and the amoeboflagellate thaumatomonads) bear silica scales on their cell surface and are relatively closely related, but apparently not sisters. They have been grouped together as the Imbricatea.
What is the name of the group of cercozoa?
Cercozoa were only recently recognised as a monophyletic group (Cavalier-Smith 1997) and were named Cercozoa in 1998 (Cavalier-Smith 1998). The name is based on the cercomonads, amoeboflagellates that are abundant in soil and freshwater, which were first discovered by Dujardin (1841) the father of protozoology, who first realised that protozoa were cells. Even earlier Dujardin (1835) had discovered the reticulose testate cercozoan amoeba Gromia. Cercomonad means ‘tailed monad’, because almost all cercomonads have an extensible pseudopodial tail that is typically drawn out along the posterior gliding cilium, sometimes obscuring it. Dujardin coined the name Rhizopoda (root feet) for organisms having filose or reticulose pseudopods. Unfortunately other authors later confusingly expanded that term to include also the unrelated Amoebozoa, which generally have broad lobose, non-root-like pseudopods. Cercozoa are now known to be one of the most diverse, speciose and ecologically important of all protozoan phyla and include the majority (not all) of eukaryotes with filose pseudopods or cilia that glide on surfaces instead of swimming (Cavalier-Smith and Chao 2003). Many lineages are currently known only from environmental DNA sequencing (Bass and Cavalier-Smith 2004; Bass et al. 2009), so cercozoan diversity must be even greater than is now appreciated.
What is the supergroup of Retaria and Cercozoa?
Irrespective of the uncertainty over the precise position of Foraminifera, and thus the monophyly of Retaria and Cercozoa, the grouping of Retaria and Cercozoa as the supergroup Rhizaria is extremely robust. This makes it highly probable that the common ancestor of both Cercozoa and Retaria was a marine benthic amoeboflagellate protozoan with reticulose pseudopods. The name Rhizaria was chosen for this supergroup to perpetuate Dujardin’s idea enshrined in his name Rhizopoda, that slender root-like pseudopods were extremely important for the motility, feeding and general life style of a major group of eukaryotes (Cavalier-Smith 2002). Such tenuous root-like pseudopods can ramify around sediment particles and over surfaces to catch bacteria or eukaryotic prey over large areas or volumes with a minimal investment in protoplasm.
What are the phylogenetic patterns of Filosa?
Within Filosa there are similarly interesting phylogenetic patterns and marine-freshwater dichotomies, some major lineages (e.g. chlorarachneans) being exclusively marine, and others exclusively soil/freshwater (e.g. cercomonads and glissomonads, two groups of zooflagellate gliders). The basal branching order of Filosa is poorly resolved, suggesting very rapid radiation of the major lineages. Four early diverging early-diverging lineages are the zooflagellates that glide on both cilia, the chlorarachnean algae, the marine metromonad gliding flagellates (possibly including the metopiids), and the Granofilosea (naked filose amoebae with granular pseudopods). They all appear to have mutually diverged before cercomonads evolved. The other testate filose amoebae (euglyphids, tectofilosids) are phylogenetically interspersed amongst the large cluster of zooflagellates that has long ciliary transitional regions and dense upper plates (Thaumatomonadida, Spongomonadida, Cryomonadida, Glissomonadida, Pansomonadida). There are weak indications that Glissomonadida are sisters to Pansomonadida and that sainouroids (zooflagellates with exceptionally short centrioles and transition regions and vestigial anterior cilia) may be related to one or both of them and that Thaumatomonadida and Spongomonadida may be sisters, but multigene evidence is essential to resolve the branching order within the long-transition region cluster and to confirm that they are a clade that may be sister to cercomonads.
What are the two structures of the ciliary transition region?
The ciliary transition region bears two characteristic structures absent from all other eukaryotes: the proximal hub-lattice and the distal nonagonal fibre (Cavalier-Smith et al. 2008). In most Cercozoa the ciliary transition region (which lies between where the centriolar triplets end and the ciliary centre pair begins) is very short, but in a few groups that constitute a single derived clade (together with related amoebae) it is rather long, and their nonagonal fibre is obscured by a dense upper transitional plate (Spongomonadida, Thaumatomonadida, Cryomonadida, Pansomonadida, Glissomonadida). The anterior cilium is younger, and the posterior cilium the mature one; thus ciliary transformation occurs over two cell cycles as in other bikont eukaryotes. Cilia typically lack scales (except for the Thaumatomastix anterior cilium) or hairs; simple non-tubular hairs are present in some Allas (anterior) and in Aurigamonas (posterior).
What is an extrusome?
Extrusomes (typically simple and rounded; more elongate in thaumatomonads; very long in cryomonads) are widely present in filosan flagellates and in granofilosans, but not in other cercozoan amoebae.
Is Endomyxa a marine parasite?
Within Endomyxa, the marine parasites of invertebrates (Ascetosporea) seem to be more closely related to the reticulose marine Gromia and Filoreta . Unsurprisingly, the land-plant parasites are closer to the predominantly terrestrial aconchulinid reticulose amoebae such as Arachnula and Platyreta that tend to eat fungi or algae. Thus parasitism evolved independently in the plant and animal parasites and their plasmodial body form is a convergent adaptation to parasitism; plasmodiophorids retained zoospores for dispersal; Ascetosporea did not.
What is a cercozoa?
The Cercozoa are a group of single-celled eukaryotes. They lack shared morphological characteristics at the microscopic level, [5] being defined by molecular phylogenies of rRNA and actin or polyubiquitin. [6]
What are the groups of amoebae that form a reticulating net?
Another important group placed here are the chlorarachniophytes, strange amoebae that form a reticulating net. They are set apart by the presence of chloroplasts, which apparently developed from an ingested green alga. They are bound by four membranes and still possess a vestigial nucleus, called a nucleomorph. As such, they have been of great interest to researchers studying the endosymbiotic origins of organelles.
Why do scientists look at radiolarian shells?
Also, because these shells react differently to chemicals and are quickly buried by new shells, researches can look at radiolarian shells and determine the global temperature, levels of oxygen, amount of volcanic activity and other things about climates five hundred million years ago. Cercozoans.
What happens to radiolarians when they die?
When radiolarians die, their silica shells sink to the ocean floor. Since radiolarians are so common, we're actually talking about hundreds of thousands of these tiny shells being deposited, and in some places they can form layers up to one hundred meters thick! The silica in these shells builds up what is called a siliceous ooze, which is both really cool to think about and really fun to say. Siliceous ooze. Come on, say it with me. Siliceous ooze. Anyway, these dense layers of sediment, made of millions of tiny radiolarian shells are a major part of the fossil record. Also, because these shells react differently to chemicals and are quickly buried by new shells, researches can look at radiolarian shells and determine the global temperature, levels of oxygen, amount of volcanic activity and other things about climates five hundred million years ago.
What is the purpose of Rhizarians?
Rhizarians are categorized by a specific kind of pseudopodia that are thin and needle-like. What is their purpose? Partly to catch food and partly for locomotion. These things help the rhizarians get around. So, what do you say? Want to see some rhizarians upclose and personal? We're at the right place, but to experience microorganisms we need to get down to their scale. This is going to be one trip to the beach you'll never forget!