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Dicranastrum furcatum.
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A colonial spumellarian radiolarian (Collosphaera sp.) composed of numerous central capsules (purple porous spheres) connected to one another by cytoplasmic strands and enclosed in a clear gelatinous sheath secreted by the radiolarian cytoplasm.
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Sphaerozoum (sphere-owe-zoo-um), detail of the surface of a colony, in which many individual organisms can be seen. In the centre of each of the bright regions is the capsule. This is an example of one of the four types of large amoebae which is common in the marine water column. Dark ground image by Dave Caron.
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A living specimen of a spherical spumellarian radiolarian (Styptosphaera sp.) showing the spherical central capsule enclosed by a spongiose siliceous shell. Numerous cytoplasmic strands (axopodia) radiate outward from the central capsule and bear patches of golden-pigmented algal symbionts.
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Collozoum - a colonial radiolarian, the bright spots being the central capsules of the organisms which make up the colony. Up to 5000 capsules may be present in a colony. These colonies are like long sausages up to several centimetres in length. There is a sheath of organic material, and this may be referred to as gelatin. The colony has a segmented appearance because the components of the colony lie in a matrix around large vacuoles or alveoli. This is an example of one of the four types of large amoebae which is common in the marine water column. Image by Dave Caron.
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Collozoum, a colonial radiolarian, the bright spots being the central capsules of the organisms which make up the colony. Up to 5000 capsules may be present in a colony. These colonies are like long sausages up to several centimetres in length. The colony has a segmented appearance because the components of the colony lie in a matrix around large vacuoles or alveoli . This is an example of one of the four types of large amoebae which is common in the marine water column. Image by N. R. Swanberg.
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The older coenobium is articulated, the younger one not. Red dots are central capsules
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A living spumellarian radiolarian (Spongaster sp.) that secretes a quadrangular, siliceous, spongiose shell enclosing the central capsule. The greenish tint is caused by numerous algal symbionts enclosed by the peripheral cytoplasm. A halo of cytoplasmic strands (axopodia) radiates from the surface. The axopodia are used to capture food, usually small crustacea (e.g. copepods) or algae.
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Observed in a sample from the south east equatorial Pacific - huge (300 microns). Image by John Dolan.
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A scanning electron microscopic view of the shell of a nassellarian, polycystine radiolarian. The shells of nassellarian radiolaria are commonly conical or elongate and segmented. Some species, however, consist only of a tripodal arranged set of spines. The central capsule is enclosed within the very small segment at the top of the shell.
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Astrolithium (astro-lith-ee-um) is one of the more commonly encountered acantharea. These star-shaped organisms used to be grouped with polycystines and phaeodarea as radiolaria. These three groups all have inorganic skeletons to which the cytoplasm attaches, usually have an inner condensed area of cytoplasm and an outer more open region, and have a star-like morphology. Like other acantharea, the spines of Astrolithium are made of strontium salts which readily dissolve when the cells die. There are 20 radiating spines which are linked together at the centre of the cell. The outermost region of cytoplasm attaches to the arms with contractile ligaments or myonemes about halfway along their length. The cells often have an orange or brown colour because of the presence of symbiotic dinoflagellates. Phase contrast.
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Astrolithium (astro-lith-ee-um) is one of the more commonly encountered acantharea. These star-shaped organisms used to be grouped with polycystines and phaeodarea as radiolaria. These three groups all have inorganic skeletons to which the cytoplasm attaches, usually have an inner condensed area of cytoplasm and an outer more open region, and have a star-like morphology. Like other acantharea, the spines of Astrolithium are made of strontium salts which readily dissolve when the cells die. There are 20 radiating spines which are linked together at the centre of the cell. This image has been taken with polarised light so the the crystalline appearance of the arms is more evident. Phase contrast with polarised light.
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Astrolithium (astro-lith-ee-um) is one of the more commonly encountered acantharea. These star-shaped organisms used to be grouped with polycystines and phaeodarea as radiolaria. These three groups all have inorganic skeletons to which the cytoplasm attaches, usually have an inner condensed area of cytoplasm and an outer more open region, and have a star-like morphology. Like other acantharea, the spines of Astrolithium are made of strontium salts which readily dissolve when the cells die. There are 20 radiating spines which are linked together at the centre of the cell. As can be seen in this micrograph, the outermost region of cytoplasm attaches to the arms with contractile ligaments or myonemes about halfway along their length. Phase contrast.
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Astrolithium (astro-lith-ee-um) is one of the more commonly encountered acantharea. These star-shaped organisms used to be grouped with polycystines and phaeodarea as radiolaria. These three groups all have inorganic skeletons to which the cytoplasm attaches, usually have an inner condensed area of cytoplasm and an outer more open region, and have a star-like morphology. Like other acantharea, the spines of Astrolithium are made of strontium salts which readily dissolve when the cells die. There are 20 radiating spines which are linked together at the centre of the cell. The outermost region of cytoplasm attaches to the arms with contractile ligaments or myonemes about halfway along their length. Phase contrast.
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Astrolithium (astro-lith-ee-um) is one of the more commonly encountered acantharea. These star-shaped organisms used to be grouped with polycystines and phaeodarea as radiolaria. These three groups all have inorganic skeletons to which the cytoplasm attaches, usually have an inner condensed area of cytoplasm and an outer more open region, and have a star-like morphology. Like other acantharea, the spines of Astrolithium are made of strontium salts which readily dissolve when the cells die. There are 20 radiating spines which are linked together at the centre of the cell. The symbiotic dinoflagellates which give the acantharea an orange or brown colour can be seen here. Differential interference contrast.
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Astrolithium (astro-lith-ee-um) is one of the more commonly encountered acantharea. These star-shaped organisms used to be grouped with polycystines and phaeodarea as radiolaria. These three groups all have inorganic skeletons to which the cytoplasm attaches, usually have an inner condensed area of cytoplasm and an outer more open region, and have a star-like morphology. Like other acantharea, the spines of Astrolithium are made of strontium salts which readily dissolve when the cells die. There are 20 radiating spines which are linked together at the centre of the cell. This image shows a young cell attached to a larger cell. Phase contrast.
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A light microscopic view of a living nassellarian radiolarian (Eucyrtidium acuminata) showing the reddish pigmented cytoplasm within the siliceous, conical shell.
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Acrosphaera (ack-row-sphere-a) spinosa, spherical colonial radiolarian. This is an example of one of the four types of large amoebae which commonly occur in the marine water colum. Dark ground image by N. R. Swanberg.
