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 Different stages of Naegleria
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Acrasidae |
The Percolozoa are a group of colourless protozoa, including many that can transform between amoeboid, flagellate, and encysted stages. Naegleria fowleri (pronounced /nə'ɡlɪəɹiə/ (also known as "the Brain -eating amoeba" is a free-living Excavate form of Protist Animals Plants fungi, and Protists are eukaryotes (juːˈkærɪɒt or -oʊt Organisms whose cells are organized into complex The excavates are a major assemblage of Protists often known as Excavata. Professor Thomas (Tom Cavalier-Smith (born October 21 1942) FRS, FRSC, NERC Professorial Fellow is a Professor of Protozoa (in Greek πρῶτον proton "first" and ζῷα zoia "animals" are unicellular Eukaryotes (singular Amoeboids are Unicellular lifeforms that mainly consist of Contractile vacuoles, a nucleus, and cytoplasm as their basic structure Flagellates are cells with one or more whip-like organelles called flagella. These are collectively referred to as schizopyrenids, amoeboflagellates, or vahlkampfids. They also include the acrasids, a group of social amoebae that aggregate to form sporangia. A sporangium (pl sporangia) is a Plant or fungal structure producing and containing Spores Sporangia occur in angiosperms, The entire group is usually called the Heterolobosea, but this may be restricted to members with amoeboid stages.
Most Percolozoa are found as bacterivores in soil, freshwater, and on feces. There are a few marine and parasitic forms, including the species Naegleria fowleri, which can become pathogenic in humans and is often fatal. Naegleria fowleri (pronounced /nə'ɡlɪəɹiə/ (also known as "the Brain -eating amoeba" is a free-living Excavate form of Protist The group is closely related to the Euglenozoa, and share with them the unusual though not unique characteristic of having mitochondria with discoid cristae. The Euglenozoa are a large group of Flagellate protozoa They include a variety of common free-living species as well as a few important parasites some of which infect humans In Cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed Organelle found in most eukaryotic cells. Cristae (singular crista) are the internal compartments formed by the inner membrane of a Mitochondrion. The presence of a ventral feeding groove in the flagellate stage, as well as other features, suggests that they are part of the excavate group. The excavates are a major assemblage of Protists often known as Excavata.
The amoeboid stage is roughly cylindrical, typically around 20-40 μm in length. They are traditionally considered lobose amoebae, but are not related to the others and unlike them do not form true lobose pseudopods. Instead, they advance by eruptive waves, where hemispherical bulges appear from the front margin of the cell, which is clear. The flagellate stage is slightly smaller, with two or four anterior flagella anterior to the feeding groove.
Usually the amoeboid form is taken when food is plentiful, and the flagellate form is used for rapid locomotion. However, not all members are able to assume both forms. The genera Percolomonas, Lyromonas, and Psalteriomonas are known only as flagellates, while Vahlkampfia, Pseudovahlkampfia, and the acrasids do not have flagellate stages. As mentioned above, under unfavourable conditions, the acrasids aggregate to form sporangia. These are superficially similar to the sporangia of the dictyostelids, but the amoebae only aggregate as individuals or in small groups and do not die to form the stalk. The dictyostelids are a group of cellular Slime molds or social Amoebae When food (normally bacteria is readily available they take the form of individual amoebae
The Heterolobosea were first defined by Page and Blanton in 1985[1] as a class of amoebae, and so only included those forms with amoeboid stages. Cavalier-Smith created the phylum Percolozoa for the extended group, together with the enigmatic flagellate Stephanopogon[2]. Professor Thomas (Tom Cavalier-Smith (born October 21 1942) FRS, FRSC, NERC Professorial Fellow is a Professor of Stephanopogon is a peculiar marine Protozoan It closely resembles certain Ciliates and was originally classified with them but is now considered a He maintained the Heterolobosea as a class for amoeboid forms, but most others have expanded them to include the flagellates as well.
References
- ^ Page, F. C. ; R. L. Blanton (1985). "The Heterolobosea (Sarcodina: Rhizopoda), a new class uniting the Schizopyrenida and Acrasidae (Acrasida)". Protistologica 21: 121-132.
- ^ Cavalier-Smith, T. (1991). "Cell diversification in heterotrophic flagellates", in D. J. Patterson & J. Larsen: The Biology of Free-living Heterotrophic Flagellates. Oxford University Press, pp. 113-131.
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