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Peritricha (protist)
The peritrichs (Latin: Peritrichia) are a large and distinctive group of ciliates. The peritrichs were first defined by Friedrich von Stein in 1859. Initially they were considered spirotrichs, then treated as a separate category, before receiving their modern placement. Structure They are usually bell or disc shaped, with a prominent paroral membrane arising from the oral cavity and circling counter-clockwise around the anterior of the cell, accompanied by a smaller series of membranelles. The oral cavity is apical and funnel shaped, with a contractile vacuole discharging directly into it. When disturbed, the anterior of the cell can contract. The rest of the body is unciliated, except for a ''telotroch band'' circling the posterior in mobile species and stages. Order Sessilida The larger order of Peritrichia are the Sessilida. Most of these have modified posterior kinetosomes which secrete a contractile stalk. The unattached stage, called a telotroch, is mouthless. These a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryote
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacteria and Archaea (both prokaryotes) make up the other two domains. The eukaryotes are usually now regarded as having emerged in the Archaea or as a sister of the Asgard archaea. This implies that there are only two domains of life, Bacteria and Archaea, with eukaryotes incorporated among archaea. Eukaryotes represent a small minority of the number of organisms, but, due to their generally much larger size, their collective global biomass is estimated to be about equal to that of prokaryotes. Eukaryotes emerged approximately 2.3–1.8 billion years ago, during the Proterozoic eon, likely as flagellated phagotrophs. Their name comes from the Greek εὖ (''eu'', "well" or "good") and κάρυον (''karyon'', "nut" or "kernel"). E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spirotrich
The spirotrichs are a large and diverse group of ciliate protozoa. They typically have prominent oral cilia in the form of a series of polykinetids, called the adoral zone of membranelles, beginning anterior to the oral cavity and running down to the left side of the mouth. There may also be one or two paroral membranes on its right side. The body cilia are fused to form polykinetids called cirri in some, and are sparse to absent in others. Forms with cirri are common throughout soil, freshwater, and marine environments. Individuals tend to be flattened, with cirri confined to the ventral surface. These are variously used for crawling over objects, acting as feet, swimming, or assisting in food capture. They are generally divided into hypotrichs and stichotrichs, but were originally all considered hypotrichs. Forms with sparse or absent body cilia tend to be smaller and are mostly marine, but a few are common in freshwater. Again, they are generally divided into oligotr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lorica (biology)
In biology, a lorica is a shell-like protective outer covering, often reinforced with sand grains and other particles that some protozoans and loriciferan animals secrete. Usually it is tubular or conical in shape, with a loose case that is closed at one end. An example is the protozoan genus '' Stentor'', in which the lorica is trumpet-shaped. In the tintinnids, the lorica is frequently transparent and is used as domicile. '' Halofolliculina corallasia'' has a lorica that is attached as an outer structure, and into which it retracts when disturbed. There are three phases in the formation of lorica: agglomeration in a natural cast; helical extension; and stabilization. The original meaning of the word is: cuirass, a type of chest armor, originally made of leather, afterward of plates of metal or horn sewed on linen or the like. See also * Chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telotroch
Telotroch is the free-swimming stage of members of the order Sessilida. Sessilida are ciliates of the subclass Peritrichia. A sessile individual can turn into a motile one to migrate to a better place. Micscape Magazine; January 2002 |
Kinetosome
A basal body (synonymous with basal granule, kinetosome, and in older cytological literature with blepharoplast) is a protein structure found at the base of a eukaryotic undulipodium ( cilium or flagellum). The basal body was named by Theodor Wilhelm Engelmann in 1880 It is formed from a centriole and several additional protein structures, and is, essentially, a modified centriole. The basal body serves as a nucleation site for the growth of the axoneme microtubules. Centrioles, from which basal bodies are derived, act as anchoring sites for proteins that in turn anchor microtubules, and are known as the microtubule organizing center (MTOC). These microtubules provide structure and facilitate movement of vesicles and organelles within many eukaryotic cells. Assembly, structure Cilia and basal bodies form during quiescence or the G1 phase of the cell cycle. Before the cell enters G1 phase, i.e. before the formation of the cilium, the mother centriole serves as a compo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuole
A vacuole () is a membrane-bound organelle which is present in plant and fungal cells and some protist, animal, and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules including enzymes in solution, though in certain cases they may contain solids which have been engulfed. Vacuoles are formed by the fusion of multiple membrane vesicles and are effectively just larger forms of these. The organelle has no basic shape or size; its structure varies according to the requirements of the cell. Discovery Contractile vacuoles ("stars") were first observed by Spallanzani (1776) in protozoa, although mistaken for respiratory organs. Dujardin (1841) named these "stars" as ''vacuoles''. In 1842, Schleiden applied the term for plant cells, to distinguish the structure with cell sap from the rest of the protoplasm. In 1885, de Vries named the vacuole membrane as tonoplast. Function The function and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Biological Membrane
A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the cell and another. Biological membranes, in the form of eukaryotic cell membranes, consist of a phospholipid bilayer with embedded, integral and peripheral proteins used in communication and transportation of chemicals and ions. The bulk of lipids in a cell membrane provides a fluid matrix for proteins to rotate and laterally diffuse for physiological functioning. Proteins are adapted to high membrane fluidity environment of the lipid bilayer with the presence of an annular lipid shell, consisting of lipid molecules bound tightly to the surface of integral membrane proteins. The cell membranes are different from the isolating tissues formed by layers of cells, such as mucous membranes, basement membranes, and serous membranes. C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliate
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of the group (although the peculiar Suctoria only have them for part of their life cycle) and are variously used in swimming, crawling, attachment, feeding, and sensation. Ciliates are an important group of protists, common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils. About 4,500 unique free-living species have been described, and the potential number of extant species is estimated at 27,000–40,000. Included in this number are many ectosymbiotic and endosymbiotic species, as well as some obligate and opportunistic parasites. Ciliate species range in size from as little as 10 µm in some colpodeans to as much as 4 mm in length in s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SAR Supergroup
The SAR supergroup, also just SAR or Harosa, is a clade that includes stramenopiles (heterokonts), alveolates, and Rhizaria. The name is an acronym derived from the first letters of each of these clades; it has been alternatively spelled "RAS". The term "Harosa" (at the subkingdom level) has also been used. The SAR supergroup is a node-based taxon. Note that as a formal taxon, "Sar" has only its first letter capitalized, while the earlier abbreviation, SAR, retains all uppercase letters. Both names refer to the same group of organisms, unless further taxonomic revisions deem otherwise. Members of the SAR supergroup were once included under the separate supergroups Chromalveolata ( Chromista and Alveolata) and Rhizaria, until phylogenetic studies confirmed that stramenopiles and alveolates diverged with Rhizaria. This apparently excluded haptophytes and cryptomonads, leading Okamoto ''et al.'' (2009) to propose the clade Hacrobia to accommodate them. Phylogeny Based on a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mobilida
Mobilida is a group of parasitic or symbiotic peritrich ciliates, comprising more than 280 species. Mobilids live on or within a wide variety of aquatic organisms, including fish, amphibians, molluscs, cnidarians, flatworms and other ciliates, attaching to their host organism by means of an aboral adhesive disk. Some mobilid species are pathogens of wild or farmed fish, causing severe and economically damaging diseases such as trichodinosis. Morphology and Feeding As the name suggests, mobilida cells are mobile, capable of moving about on the body of a host organism, and of swimming between hosts. This sets them apart from the predominantly sessile peritrichs of the order Sessilida, such as Vorticella and Epistylis, which, during the feeding, or vegetative, phase of the life cycle remain attached to submerged surfaces, often by means of a stalk. Like all peritrichs, the mobilids possess a spiral wreathe of cilia running counterclockwise around the oral region (peristome), a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
