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Didinium
''Didinium'' is a genus of unicellular ciliates with at least ten accepted species. All are free-living carnivores. Most are found in fresh and brackish water, but three marine species are known. Their diet consists largely of ''Paramecium'', although they will also attack and consume other ciliates. Some species, such as ''D. gargantua'', also feeds on non-ciliate protists, including dinoflagellates, cryptomonads, and green algae. Appearance and reproduction ''Didinia'' are rounded, oval, or barrel-shaped and range in length from 50 to 150 micrometres. The cell body is encircled by two ciliary bands, or ''pectinelles'', an upper band and a lower band just below the midline. This distinguishes them from the related genus '' Monodinium'', which have only a single band, except during cell division. The pectinelles are used to move ''Didinium'' through water by rotating the cell around its axis. At the anterior end, a cone-shaped structure protrudes, supported by a palisade ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Paramecium
''Paramecium'' ( , , plural "paramecia" only when used as a Common name, vernacular name) is a genus of eukaryotic, unicellular ciliates, widespread in freshwater, brackish, and Ocean, marine environments. Paramecia are often abundant in stagnant basins and ponds. Because some species are readily cultivated and easily induced to sexual conjugation, conjugate and divide, they have been widely used in classrooms and laboratories to study biological processes. ''Paramecium'' species are commonly studied as model organisms of the ciliate group and have been characterized as the "laboratory rat, white rats" of the phylum Ciliophora. Historical background ''Paramecium'' were among the first ciliates to be observed by microscopy, microscopists, in the late 17th century. They were most likely known to the Dutch pioneer of protozoology, Antonie van Leeuwenhoek, and were clearly described by his contemporary Christiaan Huygens in a letter from 1678. The earliest known illustration of a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Ciliate
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different wikt:undulating, undulating pattern than flagella. Cilia occur in all members of the group (although the peculiar Suctoria only have them for part of their biological life cycle, 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, including anoxic and oxygen-depleted habitats. 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 Ectosymbiosis, ectosymbiotic and endosymbiotic species, as well as some Obligate parasite, obligate and Facultative paras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Litostomatea
The Litostomatea are a class of ciliates. The group consists of three subclasses: Haptoria, Trichostomatia and Rhynchostomatia. Haptoria includes mostly carnivorous forms such as '' Didinium'', a species of which preys primarily on the ciliate ''Paramecium''. Trichostomatia (trichostomes) are mostly endosymbionts in the digestive tracts of vertebrates. These include the species '' Balantidium coli'', which is the only ciliate parasitic in humans. The group Rhynchostomatia includes two free-living orders previously included among the Haptoria, but now known to be genetically distinct from them, the Dileptida and the Tracheliida. Morphology In litostomes, the body cilia arise from structures in the cell cortex called monokinetids, which are made up of a single cilium and its associated structures, such as basal bodies and microtubular fibres. These have an ultrastructural arrangement characteristic to the group. The cell "mouth" (cytostome) is apical or subapical. In trichostomes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Vladimir Timofeyevich Szewiakow
Vladimir Timofeyevich Shevyakov (; 29 October 1859, St. Petersburg – 18 October 1930, Irkutsk) publishing under the German spelling of his name as W. Shewiakoff, was a Russian biologist who worked on Protozoa, and a professor. Shevyakov studied under Konstantin Mereschkowski in St. Petersburg and Otto Bütschli at the University of Heidelberg. He was married to Lydia Kovalevskaya, the youngest daughter of Alexander Kovalevsky. Shevyakov, together with Konstantin Arsenyev, was editor-in-chief of additional volumes of the ''Brockhaus and Efron Encyclopedic Dictionary''. He was a professor at St. Petersburg University until 1911 when he left science and became a vice-minister in the government of Tsar Nicholas. During the revolution he and his family moved first to Perm in Ural and in 1920 he became professor in Irkutsk. He is mainly known for his work on Radiolaria, Ciliata and Acantharea. He described many taxa. Works Über die karyokinetische Kerntheilung der ''Euglypha a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Contractile Vacuole
A contractile vacuole (CV) is a sub-cellular structure (organelle) involved in osmoregulation. It is found predominantly in protists, including unicellular algae. It was previously known as pulsatile or pulsating vacuole. Overview The contractile vacuole is a specialized type of vacuole that regulates the quantity of water inside a cell. In freshwater environments, the concentration of solutes is hypotonic, lower outside than inside the cell. Under these conditions, osmosis causes water to accumulate in the cell from the external environment. The contractile vacuole acts as part of a protective mechanism that prevents the cell from absorbing too much water and possibly lysing (rupturing) through excessive internal pressure. The contractile vacuole, as its name suggests, expels water out of the cell by contracting. The growth (water gathering) and contraction (water expulsion) of the contractile vacuole are periodical. One cycle takes several seconds, depending on the sp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Cytostome
A cytostome (from ''cyto-'', cell and ''stome-'', mouth) or cell mouth is a part of a cell specialized for phagocytosis, usually in the form of a microtubule-supported funnel or groove. Food is directed into the cytostome, and sealed into vacuoles. Only certain groups of protozoa, such as the Ciliophora and Excavata, have cytostomes. An example is '' Balantidium coli'', a ciliate. In other protozoa, and in cells from multicellular organisms, phagocytosis takes place at any point on the cell or feeding takes place by absorption. Structure The cytostome forms an invagination on the cell surface and is typically directed towards the nucleus of the cell.Okuda, Kendi, et al. "The cytostome of Trypanosoma cruzi epimastigotes is associated with the flagellar complex." Experimental parasitology 92.4 (1999): 223-231. The cytostome is often labeled as the entire invagination, but in fact the cytostome only constitutes the opening of the invagination at the surface of the cell. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Macronucleus
A macronucleus (formerly also meganucleus) is the larger type of nucleus in ciliates. Macronuclei are polyploid and undergo direct division without mitosis. It controls the non-reproductive cell functions, such as metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co .... During conjugation, the macronucleus disintegrates, and a new one is formed by karyogamy of the micronuclei. Macronuclei contain hundreds to thousands of chromosomes, each present in many copies. There is no mechanism to precisely partition this complex genome equally during nuclear division; thus, how the cell manages to maintain a balanced genome after generations of divisions is unknown. See also * Micronucleus References . Cell nucleus Ciliate biology {{Ciliate-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Asexual Reproduction
Asexual reproduction is a type of reproduction that does not involve the fusion of gametes or change in the number of chromosomes. The offspring that arise by asexual reproduction from either unicellular or multicellular organisms inherit the full set of genes of their single parent and thus the newly created individual is genetically and physically similar to the parent or an exact clone of the parent. Asexual reproduction is the primary form of reproduction for single-celled organisms such as archaea and eubacteria, bacteria. Many Eukaryote, eukaryotic organisms including plants, animals, and Fungus, fungi can also reproduce asexually. In Vertebrate, vertebrates, the most common form of asexual reproduction is parthenogenesis, which is typically used as an alternative to sexual reproduction in times when reproductive opportunities are limited. Some Monitor lizard, monitor lizards, including Komodo dragons, can reproduce asexually. While all prokaryotes reproduce without the fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Anal Pore
The anal pore or cytoproct is a structure in various single-celled eukaryotes where waste is ejected after the nutrients from food have been absorbed into the cytoplasm. In ciliates, the anal pore (cytopyge) and cytostome are the only regions of the pellicle that are not covered by ridges, cilia or rigid covering. They serve as analogues of, respectively, the anus and mouth of multicellular organisms. The cytopyge's thin membrane allows vacuoles to be merged into the cell wall and emptied. Location The anal pore is an exterior opening of microscopic organisms through which undigested food waste, water, or gas are expelled from the body. The anal pore is located on the ventral surface, usually in the posterior half of the cell. The anal pore itself is actually a structure made up of two components: piles of fibres, and microtubules. This structure is found in different unicellular eukaryotes like paramecium organelles. Function Digested nutrients from the vacuole pass ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
Biological Reproduction
Reproduction (or procreation or breeding) is the biological process by which new individual organisms – "offspring" – are produced from their "parent" or parents. There are two forms of reproduction: asexual and sexual. In asexual reproduction, an organism can reproduce without the involvement of another organism. Asexual reproduction is not limited to single-celled organisms. The cloning of an organism is a form of asexual reproduction. By asexual reproduction, an organism creates a genetically similar or identical copy of itself. The evolution of sexual reproduction is a major puzzle for biologists. The two-fold cost of sexual reproduction is that only 50% of organisms reproduce and organisms only pass on 50% of their genes.John Maynard Smith ''The Evolution of Sex'' 1978. Sexual reproduction typically requires the sexual interaction of two specialized reproductive cells, called gametes, which contain half the number of chromosomes of normal cells and are created by me ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] [Amazon] |
