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Centers for Disease Control/Division of Parasitic Diseases and Malaria
EOL staff
Life cycle of Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense, cause of African Sleeping SicknessDuring a blood meal on the mammalian host, an infected tsetse fly (genus Glossina) injects metacyclic trypomastigotes into skin tissue (trypomastigotes are the characteristic developmental stage that infects humans. The parasites enter the lymphatic system and pass into the bloodstream (1). Inside the host, they transform into bloodstream trypomastigotes (2), are carried to other sites throughout the body, reach other blood fluids (e.g., lymph, spinal fluid), and continue to replicate by binary fission (3). The entire life cycle of this parasite is represented by extracellular stages. The tsetse fly becomes infected with bloodstream trypomastigotes when taking a blood meal on an infected mammalian host (4,5). In the fly’s midgut, the parasites transform into procyclic trypomastigotes, multiply by binary fission (6), leave the midgut, and transform into epimastigotes (7). The epimastigotes reach the fly’s salivary glands and continue multiplication by binary fission (8). The cycle in the fly takes approximately 3 weeks. Humans are the main reservoir for Trypanosoma brucei gambiense, but this species can also be found in animals. Wild game animals are the main reservoir of T. b. rhodesiense. The subspecies Trypanosoma brucei brucei infects domestic and wild animals but usually not humans (but see the phylogeographic analysis by Balmer et al. 2011, which concludes that the three "subspecies"of T. brucei are not actually genetically or historically distinct lineages).From
Centers for Disease Control Parasites and Health website.
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Phacus (fake-us) is a genus of autotrophic euglenids. It can be distinguished from Euglena by being flattened or twisted and rigid. The most species of the genus are flat and leaf-shaped often with ridges or fins running helically or longitudinally. The chloroplasts are small, discoid and pyrenoids are usually absent. There is a single red eyespot and one locomotive flagellum. Phacus contains conspicuous paramylon bodies, mostly with one ore two large bodies in the centre of the cell. The genus is common in freshwater ecosystems, in muds and associated with detritus. This specimen was collected in freshwater ponds near Konstanz, Germany. Phacus skujai is a small member of the genus. The cells are slender and ovoid. The large paramylon body (often accompanied by a second smaller body) in the mid-cell and the short spine point to the ventral side are said to be distinctive for the species. 28 µm.
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Heteramoeba clara Droop, 1962. The flagellate stage can form a more or less spherical cell up to 30 microns in diameter. There are two equal nearly equal flagella, 60 microns long, held, as far as one can see, tangentially when the organism is moving, they cause the cell to rotate about the axis of forward motion with a period varying from about a second in the larger, to a quarter of a second in the smaller individuals. There is deep cytostome, a furrow lying between the main body and a curved enfolding collar: In the globular mature cell the collar forms an incomplete circle around what appears to be the anterior pole, with the flagellar insertion at the outer edge of one end of it, but it is clear from smaller pyriform cells that the true orientation of collar and cytostome is lateral. The cytoplasm is clear in the absence of ingested food: there are no contractile vacuoles and no stigma or chloroplasts, but the large spherical, empty nucleus is conspicuous in the anterior part of the cell. It lies very close to the flagellar insertion and is surrounded mostly towards the rear, by a layer of small highly refractive inclusions. The cell membrane is firm, but can easily be deformed when food taken in, the cytostomal collar especially is so elastic as to enable the flagellate to surround and engulf prey twice its riormal size.
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Monocercomonoides are small oval to pyriform oxymonad flagellates (5-15 µm) with four flagella separated in two pairs, one trailing flagellum. Anterior large nucleus capped with a pelta. The axostyle originates from a preaxostyle stretched between the two pairs of flagellar base, it traverses the cell and protrudes posteriorly. A thin fiber or funis follows the adhering zone of the recurrent flagellum. Phagocytoses wood particles and bacteria. Occurs as endocommensal in vertebrates and invertebrates gut such as rumen, caecum of rodents, gut of termites, larvae of xylophagous insects. This species (unidentified) from from Porotermes adamsoni (phase contrast).
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Surface view of Euglena acus (Ehrenberg,1830). Cell body is an elongate cylinder with a sharply pointed posterior end. The flagellum is about one-fourth the body length; Delicate pellicular striations are visible here. The small discoid chloroplasts are numerous. Paramylon bodies are rod-shaped. The nucleus is central. The stigma is prominent. Moves sluggishly among debris. Collected from a freshwater pond near Boise, Idaho. September 2006.DIC
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Stephanopogon apogon (steff-anne-owe-poe-gone) is a marine genus of uncertain affinities and include a small handful of species. Cells are dorso-ventrally flattened, with a wide anterior mouth which may or may not have some barbs. It moves by using flagella which are laid out in longitudinal rows. For a long time erroneously considered to be a primitive ciliate (distinguished from real ciliates because it does not have macronuclei and micronuclei). Eats diatoms and detritus. Phase contrast.
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Stephanopogon apogon (steff-anne-owe-poe-gone) is a marine genus that was recently placed in the Heterolobosea. ATCC culture 50096.
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Motion study of Distigma proteus. Scale bar indicates 50 µm. Sample from the pond Hegne Moor situated in the vicinity of Lake Constance (Bodensee, Southern Germany). Images were taken using Zeiss Universal with Olympus C7070 CCD camera.
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Centers for Disease Control/Division of Parasitic Diseases and Malaria
EOL staff
Life cycle of Leishmania protozoans, the cause of leishmaniasis in humansProtozoans in the family Leishmania are well known as the cause of
leishmaniasis in humans.
Leishmaniasis is transmitted by the bite of infected female phlebotomine sandflies (Psychodidae:Phlebotominae). The sandflies inject the infective stage (i.e., promastigotes) from their proboscis during blood meals (1). Promastigotes that reach the puncture wound are phagocytized by macrophages (2) and other types of mononuclear phagocytic cells. Progmastigotes transform in these cells into the tissue stage of the parasite (i.e., amastigotes) (3), which multiply by simple division and proceed to infect other mononuclear phagocytic cells (4). Parasite, host, and other factors affect whether the infection becomes symptomatic and whether cutaneous or visceral leishmaniasis results. Sandflies become infected by ingesting infected cells during blood meals (5,6). In sandflies, amastigotes transform into promastigotes, develop in the gut (7) (in the hindgut for leishmanial organisms in the Viannia subgenus; in the midgut for organisms in the Leishmania subgenus), and migrate to the proboscis (8).From
Centers for Disease Control Parasites and Health website.
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Phacus (fake-us) is a genus of autotrophic euglenids. It can be distinguished from Euglena by being flattened or twisted and rigid. The most species of the genus are flat and leaf-shaped often with ridges or fins running helically or longitudinally. The chloroplasts are small, discoid and pyrenoids are usually absent. There is a single red eyespot and one locomotive flagellum. Phacus contains conspicuous paramylon bodies, mostly with one ore two large bodies in the centre of the cell. The genus is common in freshwater ecosystems, in muds and associated with detritus. This specimen was collected in freshwater ponds near Konstanz, Germany. Phacus skujai is a small member of the genus. The cells are slender and ovoid. The large paramylon body (often accompanied by a second smaller body) in the mid-cell and the short spine point to the ventral side are said to be distinctive for the species. These cells are 'starved', the large paramylon body is considerably reduced and the nucleus is visible. 28 µm.
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Monocercomonoides are small oval to pyriform oxymonad flagellates (5-15 µm) with four flagella separated in two pairs, one trailing flagellum. Anterior large nucleus capped with a pelta. The axostyle originates from a preaxostyle stretched between the two pairs of flagellar base, it traverses the cell and protrudes posteriorly. A thin fiber or funis follows the adhering zone of the recurrent flagellum. Phagocytoses wood particles and bacteria. Occurs as endocommensal in vertebrates and invertebrates gut such as rumen, caecum of rodents, gut of termites, larvae of xylophagous insects. This species (unidentified) from from Porotermes adamsoni (phase contrast).
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Euglena spirogyra (EHRENBERG, 1831), elongate gliding species distinguished by warty surface. This species with numerous paramylon granules, but two of these are very large. From freshwater pond near Boise, Idaho.
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Stephanopogon apogon (steff-anne-owe-poe-gone) is a marine genus of uncertain affinities and include a small handful of species. Cells are dorso-ventrally flattened, with a wide anterior mouth which may or may not have some barbs. It moves by using flagella which are laid out in longitudinal rows. This organism was for a long time through to be a ciliate - because it looks like a ciliate. But examination of the cellular organization revealed that it s internal architecture was very different to that of ciliates - and they don t have two kinds of nuclei - like ciliates. Like many ciliates, it has flagella in rows or kineties. The anterior margin is the mouth, and the eat bacteria. Differential interference contrast.
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Stephanopogon (steff-anne-owe-poe-gone) is a marine genus of uncertain affinities and include a small handful of species. Cells are dorso-ventrally flattened, with a wide anterior mouth which may or may not have some barbs. This is one of the species with barbs. It moves by using flagella which are laid out in longitudinal rows. For a long time considered to be a primitive ciliate (distinguished from real ciliates because it does not have macronuclei and micronuclei), but ciliate affinities have subsequently been rejected. Eats diatoms and detritus. Phase contrast.
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Portrait of the euglenid flagellate, Eutreptia viridis (Perty, 1852). The cells are fusiform during swimming. The pellicle shows fine spiral striations. There are two equal length emergent flagella. The cells swim rapidly with the anterior end tracing a wide circle. When cells stop swimming they exhibit marked metaboly (euglenoid movement). There are numerous bright green discoid to ellipsoid chloroplasts. Paramylon granules are rod or disc-shaped. There is a prominent red eyespot associated with one of the flagella. There is an anterior subapical opening into the reservoir. A single contractile vacuole empties into the reservoir. The nucleus is central in swimming cells. Eutreptia has been most often reported from marine and brackish habitats but is also found uncommonly in fresh water.Collected from surface samples of a slow flowing organically enriched freshwater stream overgrown with duckweed (Lemnaceae) near Boise, Idaho. DIC.
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Trachelomonas (track-ell-owe-moan-ass) is an autotrophic euglenid flagellate. The genus is distinguished from others because the cells live within a loose fitting lorica with a small opening. The lorica of many species is elaborated with spikes or spines. The lorica accumulates metal salts with age, becoming brown and brittle and often obscuring the bright green colour of the chloroplasts within the cell. Red eyespot evident as dark region near the anterior of the cell. There is one emergent flagellum which emerges from the opening of the lorica. After division of the daughter cells will emerge from the opening of the lorica. Most freshwater but occasionally found in brackish habitats. Phase contrast.
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Saccinobaculus (sax-in-o-back-you-lus) (snake-in-a-sack) is a highly active oxymonad flagellate in which the massive contractile axostyle inside the cell seems to have a life of its own. Axostyle curves around the nucleus before extending the length of the cell. Four flagella emerging from anterior right corner. Endobiotic in the gut of the wood-eating cockroach, Cryptocercus. Differential interference contrast.
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Euglena spirogyra (EHRENBERG, 1831). Cell observed in freshwater habitats in the vicinity of Broome, Western Australia in September 2003. This image was taken using phase contrast optics. This work was supported by the Australian Biological Resources Study.
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Stephanopogon (steff-anne-owe-poe-gone) is a marine genus of uncertain affinities and include a small handful of species. Cells are dorso-ventrally flattened, with a wide anterior mouth which may or may not have some barbs. This is one of the species with barbs. It moves by using flagella which are laid out in longitudinal rows. For a long time considered to be a primitive ciliate (distinguished from real ciliates because it does not have macronuclei and micronuclei), but ciliate affinities have subsequently been rejected. Eats diatoms and detritus. Phase contrast.
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Eutreptiella (you-trep-tea-ella), a marine euglenid. The autotrophic euglenids (the ones with chloroplasts) are usually thought of as being freshwater organisms. A small number of species are found in marine habitats - the most commonly reported being Eutreptia (flagella equal in length) and Eutreptiella (flagella unequal in length) . Both have two or more emergent flagella, and these beat actively to propel the cell through the water. Euglenids have chlorophyll b in the plastids, and this gives them a bright green colour. The eyespot (stigma) lies outside the plastids. Euglenids are distinguished, in part, by the ridges under the cell membrane. Differential interference contrast.
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Trachelomonas (track-ell-owe-moan-ass) is an autotrophic euglenid flagellate. The genus is distinguished from others because the cells live within a loose fitting lorica with a small opening. The lorica of many species is elaborated with spikes or spines. The lorica accumulates metal salts with age, becoming brown and brittle and often obscuring the bright green colour of the chloroplasts within the cell. Red eyespot evident as dark region near the anterior of the cell. There is one emergent flagellum which emerges from the opening of the lorica. After division of the daughter cells will emerge from the opening of the lorica. Most freshwater but occasionally found in brackish habitats. Phase contrast.