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Actinophrys (ack-tin-off-riss), one of two genera of actinophryid heliozoa. Typically with many stiff radiating arms (not many are visible here) and with large central nucleus. These cells typically eat protozoa, algae and other small swimming microbes. Several cells observed from cooler locations. Differential interference contrast. Material from heated thermal sites of Nymph Creek and Nymph Lake in Yellowstone National Park, photograph by Kathy Sheehan and David Patterson.
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Portrait of Actinophrys ingesting a rotifer. Prey is immobilized by axopodial extrusomes then engulfed by pseudopodial extensions from the cell. From freshwater pond near Boise, Idaho. Phase contrast.
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Actinophrys (ack-tin-off-riss), one of two genera of actinophryid heliozoa. Typically with many stiff radiating arms and with large central nucleus. These cells typically eat protozoa, algae and other small swimming microbes.
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Scanning electron micrograph of the cyst of Actinophrys sol, from which the surrounding mucus layer has been removed. The image shows the layer of irregular siliceous plates that gives the cyst its rigidity.
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Individual cleaned and washed siliceous plates from the cyst of Actinophrys sol, whole plates observed by transmission electron-microscopy.
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Transmission electron micrograph through the wall of the cyst of Actinophrys. The outermost layer is a loose mucoid material that attached to the substrate and engages debris. Below this is a layer of siliceous scales. This is followed by four discrete organic layers, the innermost of which is arranged helicoidally.
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The cyst wall of Actinophrys has a helicoidal layer. Helicoids are used widely in biology, from the chromosomes of dinoflagellates to the body wall of nematodes. They provide flexibility and strength. They look like this when sectioned. Of course, this is not a picture of helicoids in Actinophrys, but of a cobble-stone road somewhere in France.
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Cysts of Actinophrys sol as observed live by differential interference contrast microscopu.
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Transmission electron micrograph of a thin section of an encysting Actinophrys. It shows the developing flat siliceous plates under the surface of the cell. Mucus has already started to appear around the outside of the cell, there are numerous dark extrusomes lying adjacent to the cell membrane. Food vacuoles and lipid droplets fill much of the cytoplasm between the central nucleus and the forming cyst wall.
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Transmission electron micrograph of a thin section through the surface of an encysting cell. The encystment process has just started - as can be seen from the sintered appearance of the siliceous scales. There is a layer of mucus outside the cell, extrusomes under the cell surface, and many mitochondria below the siliceous scales.
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Transmission electron micrograph through the surface of an encysting cell. The siliceous plates are becoming solid structures though are still not glassy. There is mucus outside the cell, numerous extrusomes attached to the underside of the cell membrane, and mitochondria with bleb-shaped cristae near the forming scales.
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The prey (a Colpidium cell) has been caught on the axopodia of Actinophrys. A pseudopodial funnel has begun to develop. It will extend to the Colpidium, and enclose the prey.
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The heliozoon has enclosed a Colpidium (ciliate) cell. A Polytomella (flagellate) cell is caught on the arms. Two Polytomella cells have already been lysed - a fate that will befall the ciliate. Nucleus is evident in the center of the actinophryid cell.
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Transmission electron micrograph of a thin section through an actinophryid that has ingested two Colpidium ciliates and was in the middle of digesting them. The nucleus is in the center of the cell.
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Focus on nucleus in the center of the cell. Scale bar indicates 50 µm. Sample from a pond situated in the vicinity of Lake Constance. The image was built up using several photomicrographic frames with manual stacking technique. Images were taken using Zeiss Universal with Olympus C7070 CCD camera.Image under Creative Commons License V 3.0 (CC BY-NC-SA).
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Focus on food vacuole. Scale bar indicates 50 µm. Sample from a pond situated in the vicinity of Lake Constance. The image was built up using several photomicrographic frames with manual stacking technique. Images were taken using Zeiss Universal with Olympus C7070 CCD camera.Image under Creative Commons License V 3.0 (CC BY-NC-SA).
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Actinosphaerium (act-in-o-sphere-ee-um) (=Echinosphaerium), one of the largest freshwater heliozoa, may measure up to 500 microns, often with outer layer being very vacuolated. Multiple nuclei and nucleating sites for the arms line at the interface between the inner and outer regions of cytoplasm. Yellowy zone in the centre is some food being digested - these heliozoa can consume small metazoa. Dark ground illumination.
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Actinosphaerium, the large multinucleate actinophryid heliozoon. These cells may be quite large - up to half a millimetre or so. Stiff arms (axopodia) radiate out from the body, the the outer region is highly vacuolated. Prey mostly on other protists and small metazoa. Bright field.
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Actinosphaerium, the large multinucleate actinophryid heliozoon. These cells may be quite large - up to half a millimetre or so. Stiff arms (axopodia) radiate out from the body, the the outer region is highly vacuolated. Prey mostly on other protists and small metazoa.Phase contrast micrograph.
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Portrait of Actinosphaerium, a naked, usually large heliozoan. Multiple small nuclei are located at the inner boundary of the peripheral well-demarcated layer of large vacuoles. Food vacuoles are seen in the central cytoplasm in this image. The axonemes of the tapering axopodia terminate on or near the nuclei. From freshwater pond near Boise, Idaho. Brightfield
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Isolated from Carolina Actinosphaerium culture # 29-5366. Freshwater heliozoon classified in the stramenopiles. Image by L. W. Parfrey
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Actinosphaerium (act-in-o-sphere-ee-um) (=Echinosphaerium), one of the largest freshwater heliozoa, may measure up to 500 microns, often with outer layer being very vacuolated. Arms taper from base to tip. Multiple nuclei and nucleating sites for the arms line at the interface between the inner and outer regions of cytoplasm. Brown inclusions are food vacuoles. Phase contrast illumination.
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Actinosphaerium (act-in-o-sphere-ee-um) (=Echinosphaerium), one of the largest freshwater heliozoa, may measure up to 500 microns, often with outer layer being very vacuolated. Multiple nuclei and nucleating sites for the arms line at the interface between the inner and outer regions of cytoplasm. This micrograph shows an axoneme and a nucleus - which has a round nucleolus at its centre. Differential interference contrast.